The California Department of Food and Agriculture (CDFA) is seeking comments on the appropriate pest rating for Leptosillia pistaciae, a recently discovered fungus that causes pistachio canker.
The
Department’s draft pest ranking assigns the highest Economic Impact score –
three. It assigns a medium Environmental Impact – two. This is because the
pathogen can kill an important native shrub, with possible follow-on
consequences of reduced biodiversity, disrupted natural communities, or changed
ecosystem processes.
CDFA
states that there is no uncertainty in its evaluation, but I see, and describe
here, numerous questions about the possible true extent of the invasion and
possible host range.
Comments are due
on April 4, 2020.
The
pathogen was detected in June 2019, when a habitat manager from an ecological
reserve in San Diego County noticed multiple dead lemonade berry shrubs (Rhus integrifolia) in one of the parks.
This is the first known detection of Leptosillia
pistaciae in the United States and on this host. USDA APHIS has classified Leptosillia pistaciae as a federal quarantine
pest. Rhus and Pistacia are in the same family, Anacardiaceae (cashews and sumacs).
According
to the CDFA, Leptosillia pistaciae is
the only member of this fungal genus known to be associated with disease
symptoms on plants. Other species are endophytes or found in dead plant
tissues. [It is not at all unusual for fungal species to be endophytes on some
plant hosts but pathogenic on others. A California example is Gibberella
circinata (anamorph Fusarium circinatum), which causes
pitch canker on Monterey pine (Pinus
radiata) but is an endophyte on various grass species (Holcus lanatus and Festuca
arundinacea).]
(Reminder: this is the second new pest of native species detected in California state in 2019; I blogged about an ambrosia beetle in Napa County here. )
Rhus integrifolia (lemonade berry
or lemonade sumac) is native to California. It grows primarily in the south, along
the coast – from San Diego to San Luis Obispo. However, some populations are
also found in the San Francisco Bay area. This and other sumacs are also sold
in the nursery trade.
On
pistachio trees in Italy, symptoms are observed in the winter and late spring. During
the winter dormant season, trees had gum exudation and cracking and peeling of
bark on trunks and branches. On trunks and large branches, cankers appeared
first as light, dead circular areas in the bark; subsequently they became
darker and sunken. Under the bark, cankers were discolored with necrotic
tissues; in some cases, these extended to the vascular tissues and pith. During
the active growing season, the symptomatic plants also showed canopy decline.
Inflorescences and shoots, originating from infected branches or twigs, wilted
and died. When the trunk was girdled by a canker, a collapse of the entire tree
occurred.
range map for Rhus integrifolia
On
lemonade berry, large clumps of dead
adult shrubs were observed on the edge of hiking trails. Some shrubs that had completely
dead foliage were re-sprouting from their bases. Trunks of shrubs that were not
completely dead were copiously weeping sap and fluids and showed foliage
browning and die back with symptoms of stress.
It
is thought that spores could be spread by wind, rain splashing, and the
movement of dead or dying trees, greenwaste, and infected nursery stock. Contaminated
pruning tools might also transport the spores. The possibility of a latent
phase – or perhaps asymptomatic hosts – adds to the probability of
anthropomorphically assisted spread.
I question how much effort has been put into detection surveys, especially in natural systems with native Rhus species. California has three other native sumacs: R. ovata, R. aromatica, and Malosma laurina (CNPS; full citation at the end of the blog). In addition, there are numerous other species in the family, including poison oaks (Toxicodendron spp.) and the widespread invasive plant genus Schinus.
Furthermore, some plants in the family (other than pistachios) are grown for fruit or in ornamental horticulture, including two of the native sumacs and two non-native species, Rhus glabra and R. lanceolata, cashew, mango, and smoke trees (Cotinus spp.).
Yet
CDFA confidently states that there are only two hosts and that it has been
detected in only one population – that in San Diego. This is because CDFA
considers only official records identified by a taxonomic expert and supported
by voucher specimens.
CDFA
states that the pathogen is likely to survive in all parts of the state where
pistachios are grown – primarily in the Central Valley. California supplies 98%
of the pistachios grown in the United States; the remainder is raised in
Arizona and New Mexico. California production occurred on 178,000 acres in
2012. A map is included in a flyer on production available at the url listed at
the end of this blog.
In
discussing spread potential, no mention is made of possible human-assisted
spread.
The CDFA document includes instructions for submitting comments; the deadline is April 4.
Sources:
Rhus and related
species native to California: California Native Plant Society
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
prickly pear cacti in Big Bend National Park photo by Blake Trester, National Park Service
The cacti that are such important components of desert ecosystems across nearly 2 million square miles straddling the U.S.-Mexico border are under threat from non-native insects – as I have noted in earlier blogs. Of course, cacti are important in other ecoregions, too – I wrote recently about the columnar cacti in the dry forests of Puerto Rico.
Flat-padded prickly pear cacti of the genus Opuntia are threatened by the cactus moth, Cactoblastis cactorum.
In 1989, the cactus moth was found
in southern Florida, to which it had spread from the Caribbean islands (Simonson
2005). Recently, the moth was found to have spread west as far as the Galveston,
Texas, area and near I-10 in Columbus, Texas, about 75 miles west of central
Houston (Stephen Hight, pers. com.) Two
small outbreaks on islands off Mexico’s Caribbean coast have been eradicated.
In Florida, the cactus moth has
caused considerable harm to six native species of prickly pear, three of which
are listed by the state as threatened or endangered.
When the cactus moth reaches the
more arid regions of Texas, it is likely to spread throughout the desert
Southwest and into Mexico. In the American southwest, 31 Opuntia species are at risk; nine of them are endemic, one is endangered.
Mexico is the center of endemism for the Opuntia
genus. In Mexico, 54 Opuntia species
are at risk, 38 of which are endemic (Varone et al. 2019; full citation at end of this blog).
The
long-term effects of the cactus moth on these North American Opuntia are unknown because there may be
substantial variations in tolerance. The attacks observed in the Caribbean
islands have shown great variability in various cactus species’ vulnerability (Varone et al. 2019).
The Opuntia cacti
support a diversity of pollinators as well as deer, javalina (peccaries),
tortoises, and lizards. Prickly pears also shelter packrats and nesting birds (which
in turn are fed on by raptors, coyotes, and snakes), and plant seedlings. Their
roots hold highly erodible soils in place (Simonson 2005).
While scientists have been concerned about the possible impacts of the cactus moth since it was detected in Florida 30 years ago, a substantial response began only 15 years later. The U.S. Department of Agriculture began trying to slow the spread of the cactus moth in 2005 (Mengoni Goñalons et al. 2014), with a focus on surveys and monitoring, host (cactus) removal, and release of sterile males. This program was successful at slowing the moth’s spread and eradicating small outbreaks on offshore islands of Alabama, Mississippi, and Mexico.
Cactus moth damage to native cacti in Florida photo by Christine Miller, UF/IFAS
However,
the moth continued to spread west and the program never received an appropriation from Congress. The primary funding source was a US – Mexico
Bi-National Invasive Cactus Moth Abatement Program. Both countries contributed
funds to support the research and operational program to slow the spread in the
U.S. Funds were provided through USDA Animal and Plant Health and Inspection
Service (APHIS) and the Mexican Secretariat of Agriculture, Livestock, Rural
Development, Fisheries and Food (SEGARPA). Unfortunately,
funding was reduced by both entities and became inadequate to maintain the
Bi-National Program.
Therefore, in 2012, APHIS abandoned
its regional program and shifted the focus to biocontrol. This is now
considered the only viable control measure in the desert Southwest where vulnerable
cacti are numerous and grow close together. The biocontrol project has been funded
since 2012 through the Plant Pest and Disease Management and Disaster
Prevention program (which receives funding through the Farm Bill). It has
received a total of slightly more than $2
million over seven years. More than half the funds went to the quarantine
facility to support efforts to rear non-target hosts and verify the biocontrol
agent’s host specificity. About a quarter of the funds supported complementary
work of an Argentine team (both the cactus moth and the most promising
biocontrol agent are native to Argentina). Much smaller amounts have supported
U.S.-based scientists who have studied other aspects of the cactus moth’s
behavior and collected and identified the U.S. moths being tested for their
possible vulnerability to attack by a biocontrol wasp.
Here are
details of what these dedicated scientists achieved in just the past seven
years at the relatively low cost of roughly $2 million. Unfortunately, the project now faces a funding crisis and
we need to ensure they have the resources to finish their work.
Some
Specifics of the BioControl Program
After literature reviews, extensive collections,
and studies in the cactus moth’s native habitat in Argentina (Varone et al. 2015), a newly described wasp, Apanteles
opuntiarum (Mengoni Goñalons et al. 2014), has been determined to be host
specific on Argentine Cactoblastis species and the most promising
candidate for biocontrol. Wasps were collected in Argentina and sent to
establish a colony in a quarantine facility in Florida to enable host
specificity studies on North American Lepidoptera (Varone et al. 2015).
Quarantine
host specificity studies and development of rearing technology has not been straightforward. Initially, it was
difficult to achieve a balanced male/female ratio in the laboratory-bred generations;
this balance is required to maintain stable quarantine laboratory colonies for
host range testing. This difficulty was overcome. A second challenge was high
mortality of the cactus-feeding insects collected in the Southwest that were to
be test for vulnerability to the biocontrol wasp. These desert-dwellers don’t
do well in the humid, air-conditioned climate of the quarantine facility! For
these difficult-to-rear native insects, scientists developed a molecular
genetics method to detect whether eggs or larvae of the cactus moth parasitoid were
present inside test caterpillars after they were exposed to the wasps. For easy
to rear test insects, caterpillars are exposed to the wasps and reared to
adulthood. Host specificity tests have been conducted on at least five species
of native U.S. cactus-feeding caterpillars and 11 species of non-cactus-feeding
caterpillars (Srivastava
et al. 2019; Hight pers.comm.).
To
date there has been no instance of
parasitism by Apanteles opuntiarum on either lepidopteran non-target species or
non-cactus-feeding insects in the Florida quarantine or in field collections in
Argentina (Srivastava et al.
2019; Varone et al. 2015; Hight pers.comm.).
The scientists expected to complete host-specificity testing in the coming months, then submit a petition to APHIS requesting the release of the wasp as a biocontrol agent. Unfortunately, the project’s request for about $250,000 in the current year was not funded. This money would have funded completion of the host specificity testing, preparation of a petition to APHIS in support of release of the biocontrol agent into the environment, and preparation of the release plan.
Meanwhile,
what can we expect regarding the probable efficacy of the anticipated biocontrol
program?
Some
of the wasp’s behavioral traits are encouraging. The wasp is widely present in
the range of the cactus moth, and persisted in these areas over the years of
the study. The wasp can deposit multiple eggs with each “sting”. Multiple wasps
can oviposit into each cactus moth without detriment to the wasp offspring. Unmated wasp females
produce male offspring only, whereas mated females produce mixed offspring
genders. In the field, female wasps attack cactus moth larvae in a variety of
scenarios: they wait at plant access holes to sting larvae when they come
outside to defecate; they attack larvae when they are moving on the surface of
the pads; they can sting the youngest cactus moth larvae through the thin plant
wall of mined the pads; and they enter large access holes created by older
larvae and attack larger larvae. The wasps are attracted by the frass
(excrement) left on the outside of the cactus pads by cactus moth larvae (Varone
et al. 2020).
However, I wonder about the extent
to which the cactus moth is controlled by parasitoids in Argentina. Cactoblastis eggs are killed
primarily by being dislodged during weather events (rain and wind) and by
predation by ants. First instar larvae are killed primarily by the native Argentine
cactus plants’ own defenses – thick cuticles and release of sticky mucilage when
the young larvae chew holes into the pads where they enter and feed internally.
As larvae feed and develop inside the pads, the primary cause of mortality is
natural enemies.
Of
all the parasitoid species that attack C. cactorum, A. opuntiarum
is the most abundant and important. When the larvae reach their final state (6th
instars), they leave the pads and find pupation sites in plant litter near the
base of the plants. It is at this stage that the parasitism from A.
opuntiarum is detected in the younger larvae that were attacked while
feeding inside pads. As the moth larva begins to spin silk into which to
pupate, larvae of the wasp erupt through the skin of the caterpillar and pupate
within the silk spun by the moth. Predation by generalists (ants, spiders,
predatory beetles) accounted for high mortality of the unprotected last instar
and pupae (Varone et al. 2019).
Finally,
the cactus moth has three generations per year when feeding on O. stricta in the subtropical and tropical coastal areas of the Americas
and the Caribbean. In Argentina, on its native host, the moth completes
only two generations per year (Varone et
al. 2019).
How to
Get the Program Support Needed
Opuntia in Big Bend National Park Photo by Cookie Ballou, National Park Service
To date, no organized
constituency has advocated for protection of our cacti from non-native insect pests.
Perhaps now that the Cactoblastis
moth is in Texas, the threat it represents to our desert ecosystems will become
real to conservationists and they will join the struggle. The first step is to
resolve the funding crisis so that the agencies can complete testing of the biocontrol
agent and gain approval for its release. So now there is “something people can
do” – and I hope they will step forward.
I hope Americans are not actually indifferent
to the threat that many cacti in our deserts will be killed by non-native
insects. Many are key components of the ecosystems within premier National
Parks, and other protected areas. Cacti also are beautiful treasures in
botanical gardens. I hope conservationists will agree that these threats must
be countered, and will help to ensure
funding of the final stages of the biocontrol tests.
Sources
Mengoni Goñalons, C., L. Varone, G. Logarzo, M. Guala, M.
Rodriguero, S.D. Hight, and J.E. Carpenter. 2014. Geographical range & lab
studies on Apanteles opuntiarum (hymenoptera: braconiDae) in AR, a candidate
for BC of Cactoblastis cactorum (Lepidoptera: Pyralidae) in North America. Florida
Entomologist 97(4) December 2014
Srivastava, M., P. Srivastava, R. Karan, A. Jeyaprakash,
L. Whilby, E. Rohrig, A.C. Howe, S.D. Hight,
and L. Varone. 2019. Molecular detection method developed to track the
koinobiont larval parasitoid Apanteles opuntiarum (Hymenoptera: Braconidae) imported from Argentina to control Cactoblastis cactorum (Lepidoptera:
Pyralidae). Florida Entomologist 102(2): 329-335.
Varone, L., C.M. Goñalons, A.C. Faltlhauser, M.E. Guala,
D. Wolaver, M. Srivastava, and S.D. Hight. 2020. Effect of rearing Cactoblastis cactorum on an artificial
diet on the behavior of Apanteles
opuntiarum. Applied Entomology DOI: 10.1111/jen.12731.
Varone,
L., G. Logarzo, J.J. Martínez, F. Navarro, J.E. Carpenter, and S.D. Hight.
2015. Field host range of Apanteles
opuntiarum (Hymenoptera: Braconidae) in Argentina, a potential biocontrol
agent of Cactoblastis cactorum
(Lepidoptera: Pyralidae) in North America. Florida Entomologist — Volume 98,
No. 2 803
Varone, L., M.B. Aguirre, E. Lobos, D. Ruiz Pérez, S.D. Hight, F. Palottini, M. Guala, G.A. Logarzo. 2019. Causes of mortality at different stages of Cactoblastis cactorum in the native range. BioControl (2019) 64:249–261
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
wiliwili flower photo by Forrest and Kim Starr, courtesy of creative commons
Hawaii’s
dryland forest is a highly endangered ecosystem. More than 90% of dry forests
are already lost due to habitat destruction and the spread of invasive plant
and animal species. However, a new publication documents some recovery of
wiliwili trees from one major pest. At the same time, a new pest is spreading
and killing naio, a critical dryland shrub. Both pests originated in countries that have rarely
if ever been a source of U.S. pests. This is worrying because phytosanitary
agencies have their hands full with imports from the usual sources. The role of
California as a source of invasive species in Hawai`i has long deserved federal
attention – but as far as I know has not received it.
Hope for Wiliwili Trees
The
Hawaiian endemic wiliwili tree, Erythrina
sandwicensis, occurs in lowland dry forests on all the major islands from
sea level to 600 m. Wililwili is a dominant overstory tree in these habitats.
(Unless otherwise noted, the principal source is Kaufman et al. in press – full
citation at end of blog.)
The tree has been severely affected by the introduced Erythrina gall wasp, Quadrastichus erythrinae (EGW). The gall wasp was detected on Oahu in 2005 and quickly spread to the other Hawaiian islands.
Arrival
of the EGW on Oahu was part of the insect’s rapid global range expansion. Originally from East Africa, it was first
detected in the Mascarene Islands and Singapore in 2003. At the time, it was unknown
to science. Within a few years it had spread across Asia, many Pacific islands
(including Hawai`i), and to the Americas, including Florida in 2006, Brazil in 2014
(Culik 2014), and Mexico in 2017 (Palacios-Torres 2017). Although apparently restricted
to the Erythrina genus as host, it
has lots of opportunities. This genus has 116 species distributed across
tropical and subtropical regions: 72 species in the Americas, 31 in Africa, and
12 in Asia.
The
severe damage to wiliwili (and to non-native Erythrina trees planted in urban areas and as windbreaks) prompted Hawaiian
officials to immediately initiate efforts to find a classical biological
control agent. The process moved rapidly. A candidate – a parasitic wasp
species new to science, Eurytoma
erythrinae – was found in East Africa in 2006. Host specificity testing was
carried out. Scientists quickly learned to rear the parasitic wasp in laboratories.
Release of the biocontrol agent was approved in November 2008 – only three and
a half years after the EGW was detected on Oahu.
The
biocontrol agent’s impact was quickly apparent. Establishment was confirmed
within 1–4 months at all release locations throughout Hawai`i. Reduced pest impacts
to trees were detected within two years. By 2018, only 33% of the foliage was
damaged on the majority of wiliwili trees. Damage to non-native Erythrina had also declined.
Results of Biocontrol
Agent’s Release
The
biocontrol agent’s efficacy in reducing EGW’s impacts on trees has been
evaluated for 10 years after the agent’s release. Monitoring was conducted at
sites on four of the six main islands. (The monitoring program and its findings
are described in Kaufman et al. in press).
I wonder how
many other biocontrol agents have been monitored so closely for such a long
time? Shouldn’t they all be?
Given
the uniqueness and importance of such long-term assessment, it is worth looking
at the data in detail.
1) Foliar Damage
and Tree Health
In
2008, before release of the biocontrol agent, more than 70% of young shoots in
wiliwili trees that were inspected were severely infested. The damage rating of
“severe” fell from about 80% of trees in 2008 to about 40% in 2011. About 20%
of trees surveyed – at sites on all islands – had no gall damage.
By
three years after release of the biocontrol agent (2011), mortality rates
attributed to stress from the EGW infestation for trees in natural areas fell
to 21%. Mortality rates for trees in botanical gardens was somewhat higher –
34%. Kaufman et al. proposed several
possible reasons: a) lingering presence of systemic insecticides that might
have harmed the biocontrol agents early in the releases; b) year-round sustenance
for the EGW as a result of the i) presence of alternative hosts and ii) supplemental
irrigation which maintained fresh foliage on the trees.
Less
intensive monitoring occurred during 2013 – 2018. It showed continuing substantial
suppression of EGW damage on Erythrina
foliage, although levels varied among locations. Sites with the lowest
precipitation and higher temperatures throughout the year had the slowest
recovery of wiliwili. Still, trees are now producing vegetative flushes and
healthier canopies during non-dormant periods.
2) Flower and Seed
Damage
Successful
reduction of infestations in flowers and seedpods was less immediate. Still, by
2011, seed-set had increased from less than 3% of trees setting and maturing
seed, to almost 30% with mature seed. The proportion of trees bearing
inflorescences also increased, with more than 60% of trees blooming three years
after introduction of the biocontrol agent. There was also a slow but steady
increase in seed production.
However,
in 2019, it remains unclear how infestation of seedpods will affect germination
and therefore future plant recruitment.
More
worrying, little recruitment was observed over the 10 years. Hawaiian
authorities have completed tests on, and are preparing a petition for release of,
a second biocontrol agent, Aprostocitus
nites. It is hoped that it will further suppress EGW in flowers and
seedpods.
Still, poor recruitment is likely due to the combined impacts of multiple invasive species in native environments. A significant factor is a second insect pest – a bruchid, Specularius impressithorax – which can cause loss of more than 75% of the seed crop. I hope authorities are seeking methods to reduce this insect’s impacts.
The Hawaiian species group of the IUCN has given the wiliwili tree the Reed Book designation of “vulnerable”.
Worries for Naio
naio in bloom photo by Forrest and Kim Starr, courtesy of creative commons
Naio
(Myoporum sandwicense)is an integral component of native Hawaiian
ecosystems, especially in dry forests, lowlands, and upland shrublands.
However, it is also found in mesic and wet forest habitats. Naio is found on all
of the main Hawaiian Islands at elevations ranging from sea level to 3000 m.
The loss of this species would be not only a significant loss of native biological
diversity but also a structural loss to native forest habitats.
The
invasive non-native Myoporum thrips, Klambothrips
myopori, was detected on the Big Island (Hawai‘i Island) in 2009 – four
years after it was first detected on ornamental Myoporum species in California. At the time of the California
detection, the species was unknown to science. It is now known that this
species is native to Tasmania.
The
thrips feeds on and causes galls on plants’ terminal growth and can eventually
lead to death of the plant.
For close to a decade, the Myoporum thrips was restricted to the Big Island. It has now been found on Oahu (Wright pers. comm.) Alarmed by the high mortality of plants in California, in September 2010, the Hawaii Department of Lands and Natural Resources Division of Forestry and Wildlife and the University of Hawai‘i initiated efforts to determine spatial distribution, infestation rates, and overall tree health of naio populations on the Big Island. Monitoring took place at nine protected natural habitats for four years. This monitoring program was supported by the USFS Forest Health Protection program. (See also the chapter on naio by Kaufman et al. 2019 in Potter et al. 2019 – full citation at the end of this blog.)
naio damaged by thrips photo by Leyla Kaufman, University of Hawaii
The monitoring confirmed that the myoporum thrips has spread and colonized natural habitats on the leeward side of Hawai`i Island. Infestation rates increased considerably at all sites over the duration of the four-year sampling period. Trees experiencing high infestation levels also showed branch dieback.
Medium-elevation sites (between 500–999 m) had the highest infestations and dieback: over 70% of the shoots had the worst damage.. At two sites, over 70% of the monitored trees have died.
Even
though flowers and fruits were still seen at all sites, little to no plant
recruitment was observed at these sites. Thus another plant species important
in this endangered plant community is in decline.
Few
management strategies are available for this pest. They include preventing
spread to other islands and early detection followed by rapid application of pesticides.
Implications
and Conclusions
The Erythrina gall wasp and myoporum thrips are only two of the thousands of invasive species established in Hawai`i. Island ecosystems, especially Hawai`i, are well recognized as especially vulnerable to invasive species. It has been estimated that on average 20 new arthropod species become established in Hawai`i every year.
East Africa and Tasmania are new sources for invasive species. Phytosanitary agencies need to adjust their targetting of high-risk imports to recognize this reality. Regarding the Hawaiian introduction of the thrips, there was probably made an intermediary stop in California – which is not unusual. (See also ohia rust.)
I
applaud Hawaiian officials’ quick action to counter these pests. I wish their
counterparts in other states did the same.
There
are multiple threats to Hawaii’s dry forests, including habitat modification
and fragmentation; wild fires; seed predation by rodents; predation on seeds, seedling,
and saplings by introduced ungulates (e.g.
feral goats, pigs and deer); competition with invasive weeds; and damage by
invasive insect pests and diseases.
With
so much of Hawaii’s dry forests already lost, the release of biocontrol agents
targetting specific pests is only one element of a much-needed effort. Long-term protection of wiliwili and naio
depends on greater efforts to reduce all threats and to stimulate natural
regeneration of this ecosystem. These programs could include predator-proof
fencing to keep out ungulates; baiting rodents and snails; and active
collection. Breeding, and planting of threatened plant species in an effort to
protect both the individual species and the habitat.
Kaufman,
L.V., J. Yalemar, M.G. Wright. In press. Classical biological control
of the erythrina gall wasp, Quadrastichus erythrinae, in Hawaii.: Conserving an
endangered habitat. Biological Control. Vol. 142,
March 2020
Potter,
K.M. B.L. Conkling. 2019. Forest Health Monitoring: National Status, Trends,
and Analysis 2018. Forest Service Research & Development Southern Research
Station General Technical Report SRS-239
Kaufman,
L.V, E. Parsons, D. Zarders, C. King, and R. Hauff. 2019. CHAPTER 9. Monitoring
Myoporum thrips, Klambothrips myopori (Thysanoptera: Phlaeothripidae), in
Hawaii
Wright, Mark. 2005. Assistant
Professor and Extension Specialist, University of Hawaii. Personal
communication.
The National Park Service has a legal mandate to manage lands and waters under its jurisdiction so as to “preserve unimpaired” their natural and cultural resources (NPS Organic Act 54 U.S.C. § 100101, et seq.) Invasive species undermine efforts to achieve that mission. In 2000, the NPS adopted a program to coordinate management of invasive plants. It’s not as effective as needed – see the strategic plan.
However, only recently has NPS begun trying to prioritize and coordinate programs targetting the many animals and animal diseases which threaten Park resources. These organisms range from emerald ash borer and quagga mussels; to pythons, goats, and pigs; to diseases such as white nose syndrome of bats and avian malaria in Hawai`i.
In 2017, NPS released an internal study of the pervasive threat to Park resources posed by invasive animals and discussed steps to overcome barriers to more effective responses (Redford et al., 2017; full citation at end of this blog). The Chief of the Biological Resources Division initiated this report by asking a Science Panel to evaluate the extent of the invasive animal problem, assess management needs, review best practices, and assess potential models that could serve as a service-wide organizational framework. The report was to pay particular attention to innovative and creative approaches including, but not limited to, new genomic tools. I summarized the Panel’s findings and conclusions in a blog when its report appeared in 2017.
Significantly, the
Panel’s final report states that “a general record of failure to control
invasive species across the system” was caused principally by a lack of support
for invasive species programs from NPS leadership.
This
report has now appeared in the form of a peer-reviewed article in the journal Biological Invasions by Dayer et al. 2019 (full citation at end of
this blog). Although nine of the ten authors are the same on both reports there
are substantive differences in content. For example, the journal article
reiterates the principal findings and conclusions of the Panel’s final report,
but in less blunt language.
What’s Been Watered
Down
The
toning down is seen clearly in the statements some of the panel’s six key
findings.
Finding
#1
The panel’s report says: invasive animals pose a significant threat to
the cultural and natural values and the infrastructure of U.S. national parks.
To date, the NPS has not effectively addressed the threat they pose.
Dayer et al. says: the ubiquitous presence of invasive animals in parks
undermines the NPS mission.
Finding
#2
The panel’s report says: managing
invasive animals will require action starting at the highest levels, engaging
all levels of NPS management, and will require changes in NPS culture and
capacity.
Dayer et al. says: coordinated action is required to meet the challenge.
Finding
#4
The panel’s report states: effective
management of invasive animals will require stakeholder engagement, education,
and behavior change.
Dayer et al. says: public engagement, cooperation and support is [sic]
critical.
Wording
of the other three “key findings” was also changed, but these changes are less
substantive.
Drayer
et al. also avoid the word “failure”
in describing the current status of NPS” efforts to manage invasive animal
species. Instead, these authors conclude that the invasive species threat “is
of sufficient magnitude and urgency that it would be appropriate for the NPS to
formally declare invasive animals as a service-wide priority.”
Where the
Documents Agree – Sort of
Both
the Panel’s report and Dayer et al.
state that invasive animal threats are under-prioritized and under-funded. They
say that addressing this challenge must begin at the highest levels within the
NPS, engage all levels of management, and will require investments from the NPS
leadership. Even within individual parks,
they acknowledge that staffs struggle to communicate the importance of invasive
animal control efforts to their park leadership, especially given competition with
other concerns that appear to be more urgent. And they admit that parks also
lack staff capacity in both numbers and expertise.
Also,
both the Panel’s report and Dayer et al.
urge the NPS to acknowledge formally that invasive animals represent a crisis
on par with each of the three major crises that drove Service-wide change in
the past: over-abundance of ungulates due to predator control; Yellowstone fire
crisis (which led to new wildfire awareness in the country); and recognition of
the importance of climate change.
The
Panel suggested ways to update NPS’ culture and capacity: providing incentives
for staff to (1) address long-term threats (not just “urgent” ones) and (2) put
time and effort into coordinating with potential partners, including other park
units, agencies at all levels of government, non-governmental organizations,
private landowners, and economic entities. Dayer et al. mention these barriers but does not directly mention
changing incentives as one way to overcome them.
Both
the Panel’s report and Dayer et al.
suggest integrating invasive animal threats and management into long-range
planning goals for natural and cultural landscapes and day-to-day operations of
parks and relevant technical programs (e.g., Biological Resources Division,
Water Resources Division, and Inventory and Monitoring Division).
What is Missing
from the Journal Publication
The
Panel’s final report noted the need for increased funding. It said that such
funding would need to be both consistent and sufficiently flexible to allow
parks to respond to time-sensitive management issues. It proposes several
approaches. These include incorporating some invasive species control programs
(e.g., for weeds and wood borers)
into infrastructure maintenance budgets; adopting invasive species as
fundraising challenges for non-governmental partners (e.g., “Friends of Park” and the National Park Foundation); and
adopting invasive species as a priority threat. Dayer et al. do not discuss funding issues.
The final internal report envisioned the
NPS becoming a leader on the invasive species issue by 1) testing emerging best
management practices, and 2) educating visitors on the serious threat that
invasive species pose to parks’ biodiversity. As part of this process, the
authors suggest that the NPS also take the lead in countering invasive species
denialism. Dayer et al. do not mention the issue of invasive species deniers.
Common Ground:
Status of Invasive Animals in the Parks
The
Panel’s report and Dayer et al. describe
the current situation similarly:
More than half of the National parks that responded to the internal survey (245 of the 326 parks) reported problems associated with one or more invasive animal species.
The total number of species recorded was 331. This is considered to be an underestimate since staffs often lack the ability to thoroughly survey their parks – especially for invertebrates.
Invasive species threats to Parks’ resources have been recognized for nearly 100 years. The original report notes that 155 parks reported the presence of one or more exotic vertebrate species in 1977. At that time, exotic animals were the fourth most commonly reported source of threats. In 1991, parks identified 200 unfunded projects to address exotic species, costing almost $30 million.
Only a small percentage of non-native animal invasions are under active management. Dayer et al. stated that 23% have management plans at the park unit level, and only 11% are reported as being ‘‘under control”.
Individual parks have effective programs targetting specific bioinvaders (examples are described in Redford et al; a brief summary of these efforts is provided in my previous blog.
Common Ground on
Some Solutions
The
report and Dayer et al. promote the
same steps to improve invasive animal management across the Service. Both note
that the NPS is adopting formal decision support tactics to update and
strengthen natural resource management across the board. More specific steps include
establishing
a coordination mechanism that enables ongoing and timely information sharing.
mainstreaming
invasive species issue across the NPS branches or creating a cross-cutting IAS
initiative among the Biological Resources Division, Water Resources Division,
Inventory and Monitoring Division, Climate Change Response Program, and the
regional offices.
While
both documents call on the NPS to develop and test emerging technologies, the
Panel’s final report is more detailed,
providing, in Table 5, a list of several areas of special interest, including
remotely triggered traps, species-specific toxicants, toxicant delivery
systems, drones, environmental DNA, and sterile-male releases. Dayer et al. mention eDNA and metabarcoding
for ED/RR, biocontrol, and gene drives to control invasive pathogens. (Neither
document discusses possible concerns regarding use of CRISPR and other
gene-altering technologies, other than to say there would be public concerns that
would need to be addressed.)
Both
documents note the necessity of working with resource managers beyond park
boundaries to detect and manage species before they arrive in parks. They note
that developing and operationalizing such partnerships requires time and
resources. Furthermore, invasive species prevention, eradication, and
containment programs can be effective only with public support. They suggest
strengthening NPS’ highly regarded public outreach and interpretation program
to build such support, including through the use of citizen scientists.
The
Panel’s final report said that the NPS should recognize that the condition of
the ecosystem is the objective of efforts.
Its authors recognized that achieving this goal might require
reconsidering how ecosystem management is organized within NPS so interacting
stressors (e.g., fire) and management
levers (e.g., pest eradication/suppression, prescribed fire) would be addressed.
For this, the NPS would need to create a focused capacity to address the
pressing issue of invasive animals in such a way that fosters integrated
resource management within parks, focusing on fundamental values of ecosystem
states, and not eradication targets. Dayer et
al. called for the same changes without specifically labelling “condition
of the ecosystem” as the goal.
Publication of
Dayer et al. prompted me to find out
what progress the NPS has made in responding to the “key findings” in the
Panel’s final report (neither publication calls them “recommendations”).
The
National Park Service has acted on the recommendation to appoint an “invasive
animal coordinator” within the Biological Resources Division. That person is Jennifer Sieracki. However, I wonder whether a person located in BRD is of sufficient stature to
influence agency policy across all divisions. It is not clear whether there is active
coordination with the national-level invasive plant coordinator.
Dr.
Sieriaki responded to my query by noting the following new efforts 1) to
improve outreach to partners and
the public, and 2) to expand formal and informal partnerships with local,
state, federal and tribal entities and local communities near parks.
NPS should soon finalize
two formal partnerships with other agencies and organizations for outreach and
management of invasive animal species.
NPS is working with
researchers at the US Geological Survey to expand an existing modeling tool for
identifying potential suitable habitat for invasive plant species to include
invasive insects. This will help staff focus on the most likely locations for
introductions and thus assist with early detection and control.
NPS has created a
Community of Practice so NPS employees can seek each other’s advice on addressing
invasive animal issues. A workshop of regional invasive species coordinators is
planned for the coming months to guide direction of the service-wide program
and identify other top priorities. (Seriacki pers. comm.)
I also wonder whether the NPS can achieve the top-level coordination and outreach to the public called for by both reports while complying with the terms of Public Law 116-9 – the John N. Dingle Jr. Conservation, Management, and Recreation Act, which was enacted a year ago. Title VII, Section 10(i) of this law limits spending to carry out invasive species program management and oversight to 10% of appropriated funds. Less than 15% may be spent on investigations (research), development activities, and outreach and public awareness efforts (Section 10(h)). The law does allow spending for investigations regarding methods for early detection and rapid response, prevention, control, or management; as well as inspections and interception or confiscation of invasive species to prevent in-park introductions.
For more information, see my previous criticism of NPS failure to address invasive species issues here.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
See also my earlier discussion of the new legislation here.
SOURCES
Dayer,
A.A., K.H. Redford, K.J. Campbell, C.R. Dickman, R.S. Epanchin-Niell, E.D.
Grosholz, D.E. Hallac, E.F. Leslie, L.A. Richardson, M.W. Schwartz. 2019. The
unaddressed threat of invasive animals in U.S. National Parks. Biol Invasions
Redford,
K.H., K. Campbell, A. Dayer, C. Dickman, R. Epanchin-Niell, T. Grosholz, D.
Hallac, L. Richardson, M. Schwartz. 2017. Invasive animals in U. S. National Parks:
By a science panel. Natural Resource Report NPS/NRSS/BRD/NRR—2017/1564. NPS,
Fort Collins, Colorado. Commissioned by the NPS Chief of Biological Resources
Division. https://irma.nps.gov/DataStore/DownloadFile/594922
Jennifer Sieracki, Invasive Animal Coordinator,
Biological Resources Division, National Park Service
Faith Campbell receives award for activism from National Association of State Foresters; 2016
For nearly 30 years I have documented bioinvasion threats and gaps, first in three Fading Forests reports (available here), then in five years of blogging. Here I pull together that information and suggest — in most cases reiterate — steps to address these threats and gaps. I list sources of discussion of the underlying issues – other than my reports and blogs – in references at the end of this blog.
My
first premise is: robust federal leadership is crucial:
The Constitution gives primacy to
federal agencies in managing imports and interstate trade.
Only a consistent approach can
protect trees (and other plants) from non-native pests.
Federal agencies have more
resources than state agencies individually or in any likely collective effort
— despite decades of budget and staffing cuts.
My
second premise is: success depends on a continuing, long-term effort founded on
institutional and financial commitments commensurate with the scale of the threat.
This requires stable funding; guidance by research and expert staff; and engagement
by non-governmental players and stakeholders. Unfortunately, as I discuss
below, funding has not been adequate or stable.
My third premise is that programs’ effectiveness needs to be measured, not just effort (see the NECIS document referenced at the end of the blog).
SPECIFICS
Preventing
new introductions continues to be the most effective action. Mitigating options
decrease and damages increase once a non-native pest has entered the country –
much less become established (see Lovett et
al. 2016 and Roy et al. 2014). I
recognize that preventing new introductions poses an extremely difficult
challenge given the volume and speed of international trade and the strong
economic forces supporting free trade. These challenges have been exacerbated over
several decades by the political zeitgeist – the anti-regulatory ideology, the emphasis
on “collaborating” with “clients” rather than imposing requirements through
regulations. Although the current “America First” policy might reduce import
volumes and therefore reduce the invasive species threat to some extent, the
anti-regulatory stance has only strengthened.
containers at the Port of Long Beach, California
Decades of cutting key agencies’ budgets and personnel are another factor. However, the damage to America’s natural systems is so great that we must try harder to find more effective strategies (See the Fading Forest reports; my previous blogs; Lovett et al. 2016; and APHIS annual reports – e.g., the 2019 report here)
Prevention
Despite adoption and implementation of new international and national regulations to stem pest introductions, introductions continue – although probably at a lower level than would otherwise be the case. Delays in adoption of regulations (documented in Fading Forests II and III and my two recent 30-years-in-review blogs have facilitated damaging introductions and spread.
Solutions
Stakeholders press USDA
leadership to initiate rules intended to strengthen phytosanitary protection and
expedite their completion
APHIS promote and facilitate
analysis of current programs and policies by non-agency experts to ensure the
agency is applying most effective strategies (Lovett et al. 2016).
Adoption
of insufficiently protective regulations (documented in FFII, FFIII, two
30-years-in-review blogs) – adopted in part because APHIS is trying to
“balance” trade facilitation and phytosanitary protection – has further
contributed to damaging pests’ introduction and spread.
Solutions:
Boost
priority of preventing pest introductions by amending the Congressional finding
in the Plant Protection Act [7 USC 7701(3)] as follows
Existing language: “[I]t is the
responsibility of the Secretary [of Agriculture] to facilitate exports, imports
and interstate commerce in . . . commodities that pose a risk of harboring
plant pests or noxious weeds in ways that
will reduce, to the extent practicable, as determined by the Secretary, the
risk of dissemination of plant pests and noxious weeds .… “
Amend to read as follows: “…. in ways that will reduce prevent, to the greatest extent practicable feasible, as determined by the Secretary, …” [emphasis added]
Adopt several actions to
strengthen phytosanitary protections at the point of origin (Lovett et al. 2016)
Expand
pre-clearance partnerships — as authorized for plants under Q-37 regulations
and ISPM-36
Expand
sentinel tree programs
Promote
voluntary substitution of packaging made from materials other than solid wood.
APHIS
doesn’t use the enforcement powers that it has under Plant Protection Act (see
several of my past blogs)
Solutions:
CBP inspectors search for pests in a pallet; CBP photo
APHIS follow the lead of Customs and Border Protection and begin penalizing importers on the first instance of their wood packaging not being in compliance with ISPM#15 (see blog here).
APHIS prohibit use of wood packaging by countries and importers of categories of imports that – over the 13 years since implementation – have developed a record of frequent violations of ISPM#15.
APHIS use its authority per revised Q-37 regulations to negotiate with countries that export plants to the U.S. to establish “integrated measures” programs aimed at minimizing the risk of associated pests being transported to the U.S.
APHIS use its authority per revised Q-37 to place in the “Not Authorized for Import Pending Pest Risk Assessment (NAPPRA) “limbo” category genera containing North American “woody” plants (see Roy et al. 2014; Lovett et al. 2016).
Spread within the
U.S.
The
United States lacks a coordinated system to prevent pest spread within the
country (see Fading Forests III Chapter 5). Even our strictest methods, like APHIS’s
quarantines regulating interstate movement of goods, have failed to curtail
spread of significant pests. The most obvious example is the emerald ash borer.
The regulations governing movement of the sudden oak death pathogen in the nursery trade have also failed: there have been periodic outbreaks in which the pathogen has been spread to nurseries across the country. Between 2003 and 2011, a total of 464 nurseries located in 27 states tested positive for the pathogen, the majority as a result of shipments traced from infested wholesalers. In 2019, plants exposed to the pathogen were again shipped to 18 states; eight of those states have confirmed that their plant retailers received infected plants (see my blog from summer here).
Another
serious gap is the frequent failure of APHIS and states to adopt official
programs targetting bioinvaders that will be difficult to control because of
biological characteristics or cryptic natures – even when severe impacts are
demonstrated. Recent examples include the laurel wilt disease complex, goldspotted
oak borer, polyphagous and Kuroshio shot hole borers and associated pathogens,
and even the spotted lanternfly (although the last has received significant
funds from APHIS.)
redbay killed by laurel wilt disease, Georgia; photo by Scott Cameron
Solutions:
APHIS apply much more stringent
regulations to interstate movement, based on a heightened priority for
prevention in contrast to facilitating interstate trade. E.g., prohibit nurseries on the West Coast from shipping P. ramorum hosts to states where the pathogen
is not established.
APHIS encourage states to adopt
quarantines and regulations aimed at preventing spread of invasive pests to
regions of the state that are not yet infested. For example, the sudden oak
death pathogen in California and Oregon; the borers in southern California.
APHIS abandon plans to deregulate
emerald ash borer and step up its support for state regulations on firewood.
APHIS stop dumping pests it no
longer wants to regulate onto the states through the “Federally Recognized
State Manage Phytosanitary (FRSMP) program”.
APHIS revise its policies so that
the “special needs exemption” [7 U.S.C. 7756] actually allows states to adopt
more stringent regulations to prevent introduction of APHIS-designated
quarantine pests (see Fading Forests III Chapter 3).
To help fill the gaps, the states are trying to coordinate their regulations in some important areas. The most advanced example is the voluntary Systems Approach to Nursery Certification, or SANC program. APHIS has supported this initiative, including by funding from the Plant Pest and Disease Management and Disaster Program (see below). However, it is a slow process; USDA funds first became available in 2010. The states are trying to coordinate on firewood, but we don’t yet know what the process will be.
Funding shortfalls (See the three Fading Forests
reports, my blogs about appropriations)
Increase APHIS’ access to emergency
funds from the Commodity Credit Corporation by
amending the Plant Protection Act [7 U.S.C. 7772 (a)] to include this
new definition of “emergency”:
the term “emergency” means any
outbreak of a plant pest or noxious weed which directly or indirectly threatens
any segment of the agricultural production of the United States and for which
the then available appropriated funds are determined by the Secretary to be
insufficient to timely achieve the arrest, control, eradication, or prevention
of the spread of such plant pest or noxious weed.
Although APHIS has the most
robust prevention program of any federal agency, its funding is still
inadequate. Stakeholders should lobby the Congress in support of higher annual
appropriations.
The Plant
Pest and Disease Management and Disaster Program (now under Section 7721 of the
Plant Protection Act) has provided at least $77 million for tree-pest
programs (excluding NORS-DUC & sentinel plant programs and other programs)
since FY 2008. Much useful work has been carried out with these funds. However,
these short-term grants cannot substitute for stable, long-term funding. I
reiterate my call for stakeholders to lobby the Congress to provide larger
appropriations to the APHIS Plant Protection program and Forest Service Forest
Health Protection and Research programs.
Long-term Responses
to Bioinvasive Challenge
More stakeholders are advocating raising the priority of – and providing adequate resources to – such long-term solutions as biocontrol and breeding trees resistant to pests and restoring them to our forests. Advocates include the state forestry agencies of the Northeast and Midwest, some non-governmental organizations, some academics, and individual USFS scientists. One effort resulted in inclusion of language in the 2018 Farm Bill (see blog here) – although this approach has apparently run into a dead end. The new emphasis on breeding has so far not been supported by agency or Congressional leaderships.
test planting of an American chestnut bred to be resistant to chestnut blight
Solutions:
USFS convene workshop of the
federal, state, National Academy, academic, and NGO groups promoting resistance
breeding in order to develop consensus on priorities and general structure of program.
Explicitly include evaluation of the
CAPTURE Project’s (see blog here) efforts to
set priorities to guide funding allocations and policies; and proposals for
providing needed supportive infrastructure – facilities, trained staff in
various disciplines. (See my blogs here.)
Report results of meeting to USDA
leadership, Congress, and stakeholders
Then ensure implementation of the
accepted approach by both Research and Development and Forest Health Protection
programs. Include provisions to provide sustainable funding.
These proposed actions still do not address ways to correct the provisions of the international phytosanitary agreements (World Trade Organization and International Plant Protection Convention) that complicate – or preclude – efforts to prevent introduction of pests currently unknown to science. This issue is discussed in Fading Forests II. A current example is beech leaf disease (described here).
Continuing
inadequate engagement by stakeholders
Most
constituencies that Americans expect to protect our forests don’t press
decision-makers to fix the problems I have identified above: inadequate
resources, weak and tardy phytosanitary measures. Some of these stakeholders
are other federal agencies, or state agencies – or their staffs. They face
restrictions on how “political” they can be. But where are the professional and scientific associations,
representatives of the wood products industry, forest landowners, environmental NGOs and their funders, urban
tree advocates Efforts by me, USDA, and others to better engage these groups
have had disappointing results.
As
I have documented, groups of USFS scientists have made several attempts to
document the extent of invasive species threats and impacts and to set
priorities. So far, they have not gained much traction. Another USFS attempt,
Poland et al. in press, will appear
at the end of the year. Will this be more successful?
I
detect growing attention to educating citizen scientists for early detection;
but if there is an inadequate – or no – official response to their efforts
won’t people become discouraged?
SOURCES
Lovett,
G.M., M. Weiss, A.M. Liebhold, T.P. Holmes,
B. Leung, K.F. Lambert, D.A. Orwig, F.T. Campbell, J. Rosenthal, D.G. McCullough,
R. Wildova, M.P. Ayres, C.D. Canham, D.R. Foster, SL. Ladeau, and T. Weldy.
2016. NIS forest insects and pathogens in the US: Impacts and policy options. Ecological
Applications, 26(5), 2016, pp. 1437–1455
National Environmental Coalition on Invasive Species “Tackling the Challenge.”
Poland,
T.M., Patel-Weynand, T., Finch, D., Miniat, C. F., and Lopez, V. (Eds) (2019),
Invasive Species in Forests and Grasslands of the United States: A
Comprehensive Science Synthesis for the United States Forest Sector. Springer Verlag. (in press).
Roy,
B.A., H.M Alexander, J. Davidson, F.T Campbell, J.J Burdon, R. Sniezko, and C.
Brasier. 2014. Increasing forest loss worldwide from P&Ps requires new
trade regulations. Front Ecol Environ 2014; 12(8): 457–465
dead whitebark pine in Crater Lake National Park photo by F.T. Campbell
I began studying and writing about the threat to North America’s forests from non-native insects and pathogens in the early 1990s – nearly 30 years ago. I reported my analyses of the evolving threat in the three “Fading Forests” reports – coauthored by Scott Schlarbaum – in 1994, 2003, and 2014. These reports are available here.
So what has changed over those 30 years? What remains the same? Why have both the changes and the stasis occurred? What can we do to fix the gaps, close unaddressed pathways, strengthen flabby policies? I will address these issues in this and following blogs.
experimental American chestnut planted in Fairfax County, VA photo by F.T. Campbell
What has changed
since the early 1990s:
Adoption and implementation of significant new international and national regulations and programs aimed at preventing introductions of non-native invasive species.
Despite the welter of new regulations, an alarming increase in numbers of highly damaging forest pests established in the country. (By my count, about 50 new species have established on the continent, six on Pacific islands; see details below.)
Alarming spread of established pests to new geographic regions and new hosts (e.g., emerald ash borer in 35 states and 5 provinces; laurel wilt disease across the range of redbay and swamp bay; rapid ‘ōhi‘a death on three of the main Hawaiian islands).
Introductions via unexpected pathways and vectors far removed from phytosanitary agencies’ usual targets, e.g., ship superstructures, imported steel and stone …
What has remained the
same since the early 1990s:
Inadequate
resources provided to response and recovery efforts.
Available
funding focused on only a few of the more than 90 species causing damage.
Adoption
of insufficiently protective regulations that have failed to prevent
introduction and spread of tree-killing pests.
Lengthy
delays in implementing programs that tighten controls – another factor in
continuing introductions and spread.
Continued
importance of expected pathways – nursery stock and raw wood, especially
crates, pallets, and other forms of wood packaging.
Federal
and state agencies still choose not to take action on pests e.g., goldspotted oak borer, polyphagous
and Kuroshio shothole borers, beech leaf disease.
Inadequate
coordination despite several efforts to set priorities.
Spurts
of attention by media and political decision-makers, contrasted by lengthy
periods of inattention.
Failure
of most stakeholders to support efforts to prevent and respond to introductions
of tree-killing pests.
Details: The Situations
Then and Now
(Many of the individual species mentioned here are described more fully here. Full citations of sources are at the end of blog.)
American elm on the National Mall, Washington, D.C.
photo by USDA Agricultural Research Service
In 1993:
The number of non-native forest pest species established in the U.S. was estimated at between 300 (Millers et al. 1993) and 380 (Mattson et al., 1994; Liebhold et al., 1995) .
The area suffering the greatest numbers and impacts was the Northeast.
Several highly damaging pests that had been established for decades, including chestnut blight, white pine blister rust, Port-Orford-cedar root disease, Dutch elm disease, hemlock woolly adelgid, butternut canker, and dogwood anthracnose were receiving some attention but continued to spread.
USDA Forest Service funding for management of exotic pest infestations was crisis-oriented, with “… priorities … set under political pressures for immediate answers, with too much regard for short-term problems and too little consideration for broader management objectives.” (NAS 1975)
Since few high-profile pests had been introduced in recent years, APHIS was not actively engaged. In FY92, APHIS spent $20 million on efforts to eradicate the Asian gypsy moth. The narrow focus is illustrated by the fact that in FY93, more than two-thirds of all USDA tree pest control funds were devoted to efforts to suppress or eradicate the European gypsy moth (See FFI).
Concern about possible new introductions had grown; it focused on proposals to import unprocessed wood from Siberia, New Zealand, and Chile. The USDA Forest Service, academic scientists, and therefore APHIS emphasized the risks of known Asian pests, e.g., Asian gypsy moth, to western coniferous forests (See FFI). While individual scientists had expressed concern about wood packaging material, there was little public discussion of this threat.
We would learn later that several of the most damaging pests were already present in the country but not yet recognized – Asian longhorned beetle, sudden oak death pathogen, probably emerald ash borer.
beech leaf disease
photo by John Pogacnik
In 2019:
Numbers of non-native insects and pathogens attacking trees in North America approach 500 species. (In Fading Forests III, I calculated that by the first decade of the 21st Century, the number had risen to at least 475. Several more have been detected since 2014. More than 181 exotic insects that feed on woody plants had established in Canada. (Source: USDA APHIS. 2000. Wood packaging risk assessment.)
Of these, 91 are considered “serious” threats (Guo et al. 2019). This estimate excludes pests native to portions of North America that are causing severe damage in naïve hosts – e.g., goldspotted oak borer; pests of palms; and pests attacking trees on U.S. Pacific and Caribbean islands.
Introductions had continued.
Between 1980 and 2016, at least 30 non-native species of wood- or bark-boring insects (Scolytinae / Scolytidae) were newly detected in the U.S. (Haack and Rabaglia 2013; Rabaglia et al. 2019). A few of these are highly damaging, e.g. redbay ambrosia beetle, polyphagous and Kuroshio shothole borers.
In addition to these 30 new pests, other highly damaging tree-killing pests probably introduced since the 1980s include (on the continent):
Eight Cerambycids such as Asian longhorned beetle (Wu et al. 2017)
7 Agrilus, including emerald ash borer and soapberry borer; plus goldspotted oak borer transported from Arizona to California (Digirolomo et al. 2019; R. Haack, pers. comm.)
Sirex woodwasp
Pests of palm trees, e.g., red palm mite, red palm weevil, South American palm weevil
Spotted lanternfly
Beech leaf disease
Also not included in the above estimate and lists are tree-killing pests on America’s Pacific Islands :
‘ōhi‘a rust
Cycad scale
Cycad blue betterfly
Erythrina gall wasp
two Ceratocystis pathogens that cause rapid ‘ōhi‘a death
Coconut rhinoceros beetle
Authorities also carried out approximately 25 eradication programs targetting introductions of the Asian gypsy moth (USDA Pest Alert Asian Gypsy Moth plus additional outbreaks since 2014).
Impacts of exacerbated tree mortality rates linked to these introduced pests are seen across wide swaths of the country, and affect widespread species, genera, and families.
dead redbay in Claxton, Georgia photo by Scott Cameron
I will discuss the risk of continuing new introductions in a separate blog.
Trying to Develop
the Big Picture and Set Priorities
In
recent years, USDA Forest Service scientists have made several attempts to
provide nation-wide assessments of the impact of these pests and criteria for
establishing priorities.
The
National Insect and Disease Forest Risk Assessment predicted the loss of basal
area to various pests over the 15-year time period 2012 – 2027. The assessment
predicted the following losses for specific species: 90% for redbay; 60% for whitebark
pine; more than 40% for limber pine; 24% for tanoak; 11% for coast live oak; 6%
for eastern and Carolina hemlock; 27% for eight species of ash; 20% for
American elm; 19% for red oak; 18% for American beech (Krist et al. 2014).
A separate group of scientists found that, nation-wide, non-native forest pests are causing an approximate 5% increase in total mortality by tree volume (Randy Morin at NEFPC). For details on Dr. Morin’s findings, see my blog here.
A third approach to developing a nation-wide picture, Project CAPTURE, (and my blog here) utilized FIA data to develop priorities for conservation action. Fifteen species were placed in the highest priority category, including Florida torreya (Torreya taxifolia), American chestnut and Allegheny and Ozark chinquapins, redbay, five species of ash, two species of hemlock, Port-Orford cedar, tanoak, and butternut (Potter et al. 2019(b).
According
to Project CAPTURE, the non-native pests affecting the largest number of hosts
are the European gypsy moth, which attacks 65 hosts; and oak wilt (Bretziella fagacearum), which infects 61
hosts. The Asian longhorned beetle attacks 43 hosts (Potter et al. 2019(b).
I note that several other non-native pests also have high numbers of host species. In the Project CAPTURE study, these pests are ranked lower because the project limited its evaluation to the five agents with the greatest effect on any particular host. Thus, of the 18 native tree species that host one or both of the invasive shothole borers and associated Fusarium disease complex (PSHB website), the project included only six. Of the 22 tree species listed by APHIS as hosts of Phytophtora ramorum, the project included 12 (K. Potter, pers. comm. April 17, 2019).
SOD-killed tanoak on the Big Sur peninsula, California photo by Matteo Garbelotto, University of California Berkeley
More extensive discussions of
non-native pests’ impacts are provided in Lovett et al. 2006, Lovett et al.
2016, and Potter et al. 2019. A
book-length discussion of invasive species impacts – ranging from feral hogs to
invasive plants, is expected in December; look for Poland et al. (in press).
SOURCES
Aukema,
J.E., D.G. McCullough, B. Von Holle, A.M. Liebhold, K. Britton, & S.J.
Frankel. 2010. Historical Accumulation of Nonindigenous Forest Pests in the
Continental United States. Bioscience. December
2010 / Vol. 60 No. 11
Digirolomo, M.F., E. Jendek, V.V. Grebennikov, O. Nakladal. 2019. First North American
record of an unnamed West Palaearctic Agrilus (Coleoptera:
Buprestidae) infesting European beech (Fagus sylvatica) in New York
City, USA. European Journal of
Entomology. Eur. J.
Entomol. 116: 244-252, 2019
Guo,
Q., S. Fei, K.M. Potter, A.M. Liebhold, and J. Wenf. 2019. Tree diversity
regulates forest pest invasion. Proceedings of the National Academy of Sciences
of the United States of America. www.pnas.org/cgi/doi/10.1073/pnas.1821039116
Haack,
R.A. and R.J. Rabaglia. 2013. Exotic Bark and Ambrosia Beetles in the USA:
Potential and Current Invaders. CAB International 2013. Potential Invasive
Pests of Agricultural Crops (ed. J. Peña)
Krist,
F.J. Jr., J.R. Ellenwood, M.E. Woods, A. J. McMahan, J.P. Cowardin, D.E. Ryerson,
F.J. Sapio, M.O. Zweifler, S.A. Romero 2014. National Insect and Disease Forest
Risk Assessment. United States Department of Agriculture Forest Service Forest
Health Technology Enterprise Team FHTET-14-01
Leung,
B., M.R. Springborn, J.A. Turner, E.G. Brockerhoff. 2014. Pathway-level risk
analysis: the net present value of an invasive species policy in the US. The
Ecological Society of America. Frontiers of Ecology.org
Liebhold, A. M., W. L. MacDonald, D. Bergdahl, and V. C. Mastro. 1995. Invasion by exotic forest pests: a threat to forest ecosystems. Forest Sci., Monograph 30. 49 pp.
Lovett,
G.M., C.D. Canham, M.A. Arthur, K.C. Weathers, and R.D. Fitzhugh. Forest
Ecosystem Responses to Exotic Pests and Pathogens in Eastern North America. BioScience
Vol. 56 No. 5 (May 2006)
Lovett,
G.M., M. Weiss, A.M. Liebhold, T.P. Holmes,
B. Leung, K.F. Lambert, D.A. Orwig, F.T. Campbell, J. Rosenthal, D.G.
McCullough, R. Wildova, M.P. Ayres, C.D. Canham, D.R. Foster, SL. Ladeau, and
T. Weldy. 2016. NIS forest insects and pathogens in the US: Impacts and policy
options. Ecological Applications, 26(5), 2016, pp. 1437–1455
Mattson,
W. J., P. Niemela, I. Millers, and Y. Ingauazo.
1994. Immigrant phytophagous insects on woody plants in the United
States and Canada: an annotated list.
USDA For. Ser. Gen. Tech. Rep. NC-169, 27 pp.
Millers, I. United States
Department of Agriculture, Forest Service Entomologist, Forest Health
Protection Northeastern Area State and Private Forestry. Durham, NH. Personal
communication to F.T. Campbell, 1993.
Morin, R. presentation at Northeastern Forest Pest Council 81st Annual
Meeting, March 12 – 14, 2019, West
Chester, Pennsylvania
National Academy of Sciences. 1975. Forest Pest Control. Washington, D.C.
Poland,
T.M., Patel-Weynand, T., Finch, D., Miniat, C. F., and Lopez, V. (Eds) (2019),
Invasive Species in Forests and Grasslands of the United States: A
Comprehensive Science Synthesis for the United States Forest Sector. Springer Verlag. (in press).
Potter,
K.M., M.E. Escanferla, R.M. Jetton, and G. Man. 2019. Important Insect and
Disease Threats to US Tree Species and Geographic Patterns of Their Potential
Impacts. Forests 2019, 10, 304.
Potter,
K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S. 2019. Prioritizing
the conservation needs of US tree spp: Evaluating vulnerability to forest insect
and disease threats, Global Ecology and Conservation (2019), doi:
https://doi.org/10.1016/
Rabaglia,
R.J., A.I. Cognato, E. R. Hoebeke, C.W. Johnson, J.R. LaBonte, M.E. Carter, and
J.J. Vlach. 2019. Early Detection and Rapid Response. A Ten-Year Summary of the
USDA Forest Service Program of Surveillance for Non-Native Bark and Ambrosia
Beetles. American Entomologist Volume 65, Number 1
U.S.
Department of Agriculture, Animal and Plant Health Inspection Service. 2009.
Risk analysis for the movement of wood packaging material (WPM) from
Canada into the US.
Wu,Y.,
N.F. Trepanowski, J.J. Molongoski, P.F. Reagel, S.W. Lingafelter, H. Nadel1,
S.W. Myers & A.M. Ray. 2017. Identification of wood-boring beetles
(Cerambycidae and Buprestidae) intercepted in trade-associated solid wood
packaging material using DNA barcoding and morphology Scientific Reports 7:40316
feral hogs in Missouri; photo by Missouri Department of Conservation
A new report by several experts confirms fears that the feral pig threat is widespread and re-emphasizes the value of taking action early. (I have blogged several times about efforts to manage damaged caused by feral hogs – see here and here.
Lewis
et al. (full reference at end of
blog) used two national-scale data sets to estimate historical, current, and
future potential population size of wild pigs in the U.S. from 1982 to 2016.
They
found that both wild pig distribution and abundance have nearly tripled over
this period (from ~2.4 to 6.9 million). If no effective action is taken and pigs
spread to all available habitat, the U.S.
wild pig population could reach ~21.4 million at some unspecified future date. This
would represent a 210% increase above the 2016 population; or a 784% increase
above the 1982 population.
The authors cite successful control of wild pigs in Colorado, New Mexico, Michigan, and Nebraska as evidence of the value of early detection and rapid response.
Lewis
et al. provide brief summaries of
economic and ecological damage caused by feral hogs. They damage a wide range
of ecological communities, especially riparian areas, grasslands, and deciduous
forests. Biological diversity is hurt through habitat destruction, direct
predation, and competition for resources. In addition, wild pigs can host a
suite of viruses, bacteria, and parasites, many of which can be transmitted to
other wildlife, humans, and livestock.
The
report notes that much of the recent spread of pigs has been caused by widespread
and illegal releases of wild animals for sport hunting. Other contributing factors
are land-use patterns, because hogs do well in agricultural areas. Warmer
winter temperatures and increased forest mast production are also to blame –
both related to climate-change
Wild
pigs can persist in a range of environments, including cold northern climates,
arid regions, and mixed forests. That is, all regions of the continental U.S. The
vast majority of states – especially in the West, North, and East – could see
major expansions in wild pig populations if animals are allowed to become
established over currently unoccupied habitat.
While
states that have had large established wild pig populations – e.g., Texas, California, and Florida – will
not see major expansions, damage is already severe and widespread. Texas alone
has an estimated 2.5 million feral hogs!
Preventing
the alarming expansion of feral hog populations outlined above, Lewis et al. call for adoption and
implementation of proactive management. The
priority is to quickly identify and eradicate populations that invade
unoccupied habitat. This applies particularly to those states which currently
have low populations of feral hogs.
The
same approach can be applied within states. Officials can use one data set to
identify areas where wild pigs are currently absent and the predicted
population density data to designate priority areas to counter spread. Such
efforts should include public education and outreach, regulatory enforcement,
and surveillance.
Lewis
et al. note that implementation of the
proposed strategy will require a coordinated
effort among federal, state, and local governments and the public. They
call especially for state regulations
classifying feral hogs as an invasive and harmful species supported by action
to halt pig translocation for the purposes of recreational sport hunting.
The authors promised that the findings of the study would be applied by the National Feral Swine Damage Management Program, which is led by USDA APHIS. One of the “tactics” to achieve Objective 2.4 in the APHIS Strategic Plan for 2019-2023 says the agency will “expand feral swine damage management for agricultural, livestock, property, ecological and human health and safety purposes.” Still, states will find it challenging to take any actions opposed by hunters.
At the end of June 2019, the U.S. Department of Agriculture (USDA) announced a $75 million program called the Feral Swine Eradication and Control Pilot Program (FSCP). (This works out to about $15 million per year.) The program is a joint effort by the Natural Resources Conservation Service (NRCS) and APHIS. It was established by the 2018 Farm Bill. Additional information is available at the program webpage.
The
webpage describes how to apply for funding for projects lasting up to three
years. The pilot projects will
consist broadly of three coordinated components: 1) feral swine removal by
APHIS; 2) restoration efforts supported by NRCS; and 3) assistance to producers
for feral swine control provided through partnership agreements with
non-federal partners.
The initial funding will target specific locations in the South that have experienced recent increases in wild pigs (shown on the map below). The goal is to reduce the numbers of pigs (and associated damage) in those identified localized areas of the South. These “pilot” areas have been identified by the USDA Secretary as under threat from feral swine. The first round of projects – 20 projects – are targetted at a few counties in Alabama, Arkansas, Florida, Georgia, Louisiana, Oklahoma, North Carolina, South Carolina, and Texas. APHIS has determined these states and California have highest feral swine populations.
The new program builds on successes in recent years. Funding of APHIS’ feral hog program at about $20 million per year has helped several states become “pig free”. Idaho, Iowa, Maine, New Jersey and New York are currently monitoring (using eDNA and scat dogs) to make sure that the pigs are truly gone.
SOURCE
Lewis, J.S., J.L. Corn, J.J. Mayer, T.R. Jordan, M.L. Farnsworth, C.L. Burdett, K.C. VerCauteren, S.J. Sweeney, R.S. Miller. 2019. Historical, current, and potential population size estimates of invasive wild pigs (Sus scrofa) in the United States. Biological Invasions, Vol. 21, No. 7, pp. 2373-2384.
Posted by Faith Campbell
We
welcome comments that supplement or correct factual information, suggest new
approaches, or promote thoughtful consideration. We post comments that disagree
with us — but not those we judge to be not civil or inflammatory.
frogs in California killed by chytrid fungus photo by Rick Kyper, US Fish and Wildlife Service
I expect you have heard about the report issued on May 6 by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. The executive summary is available here
Based on thousands of scientific
studies, the report concludes that the biosphere, upon which humanity as a whole
depends, is being altered to an unparalleled degree across all spatial scales. The
trends of decline are accelerating. As many as 1 million species (75% of which are
insects) are threatened with extinction, many within decades.
Humans dominate Earth: natural
ecosystems have declined by 47% on average. Especially hard-hit are inland
waters and freshwater ecosystems: only 13% of the wetland present in 1700
remained by 2000. Losses have continued rapidly since then.
The report lists the most important
direct drivers of biodiversity decline – in descending order – as habitat loss
due to changes in land and sea use; direct exploitation of organisms; climate
change; pollution; and invasive species. The relative importance of each driver
varies across regions.
If you have been paying attention, these
conclusions are not “news”.
However, the report serves two valuable
purposes. First, it provides a global overview, a compilation of all the data
and trends. Second, the report ties the direct drivers to underlying causes
which are in turn underpinned by societal values and behaviors. Specifically
mentioned are production and consumption patterns, human population dynamics
and trends, trade, technological innovations, and governance (decision making
at all levels, from local to global).
The report goes to great lengths to
demonstrate that biological diversity and associated ecosystem services are
vital for human existence and good quality of life – especially for supporting
humanity’s ability to choose alternative approaches in the face of an uncertain
future. The report concludes that while more food, energy and materials than
ever before are now being supplied to people, future supplies are undermined by
the impact of this production and consumption on Nature’s ability to provide.
The report also emphasizes that both the
benefits and burdens associated with the use of biodiversity and ecosystem
services are distributed and experienced inequitably among social groups,
countries and regions. Furthermore, benefits provided to some people often come
at the expense of other people, particularly the most vulnerable. However, there are also synergies – e.g., sustainable agricultural practices
enhance soil quality, thereby improving productivity and other ecosystem
functions and services such as carbon sequestration and water quality
regulation.
The report contains vast amounts of data
on the recent explosion of human numbers and – especially – consumption – of
agricultural production, fish harvests, forest products, bioenergy production …
and on the associated declines in “regulating” and “non-material contributions”
ecosystem services. In consequence, the report concludes, these recent gains in
material contributions are often not sustainable.
While invasive species rank fifth as a
causal agent of biodiversity decline globally, alien species have increased by
40% since 1980, associated with increased trade and human population dynamics
and trends. The authors report that nearly 20% of Earth’s surface is at risk of
bioinvasion. The rate of invasive species introduction seems higher than ever
and shows no signs of slowing.
The report notes that the extinction
threat is especially severe in areas of high endemism. Invasive species play a
more important role as an extinction agent in many such areas, especially
islands. However, some bioinvaders also have devastating effects on mainlands;
the report cites the threat of the pathogen Batrachochytrium
dendrobatidis to nearly 400 amphibian species worldwide.
The report also mentions that the combination
of species extinctions and transport of species to new ecosystems is resulting
in biological communities – both managed and unmanaged — becoming more similar
to each other — biotic homogenization.
The report notes that human-induced
changes are creating conditions for fast biological evolution of species in all
taxonomic groups. The authors recommend adopting conservation strategies
designed to influence evolutionary trajectories so as to protect vulnerable species
and reduce the impact of unwanted species (e.g.,
weeds, pests or pathogens).
The report says conservation efforts
have yielded positive outcomes – but they have not been sufficient to stem the
direct and indirect drivers of environmental deterioration. Since 1970, nations
have adopted six treaties aimed at protection of nature and the environmental,
but few of the strategic objectives and goals adopted by the treaties’ parties
are being realized. One objective that is on track to partial achievement is
the Aichi Biological Diversity Target that calls for identification and
prioritization of invasive species.
That might well be true – but I would not consider global efforts to manage invasive species to be a success story in any way. I have blogged often about studies showing that introductions continue unabated … and management of established bioinvaders only rarely results in measurable improvements. [For example, see here and here.]
The report gives considerable attention
to problems caused by some people’s simultaneous lack of access to material
goods and bearing heavier burden from pollution and other negative results of
biodiversity collapse. Extraction of living biomass (e.g. crops, fisheries) to meet the global demand is highest in
developing countries whereas material consumption per capita is highest in developed countries. The report says that
conservation of biodiversity must be closely linked to sustainable approaches
to more equal economic development. The authors say both conservation and economic
goals can be achieved – but this will require transformative changes across
economic, social, political and technological factors.
One key transformation is changing
people’s conception of a good life to downplay consumption and waste. Other
attitudinal changes include emphasizing social norms promoting sustainability
and personal responsibility for the environmental impacts of one’s consumption.
Economic measures and goals need to address inequalities and integrate impacts
currently considered to be “economic externalities”. The report also calls for inclusive
forms of decision-making and promoting education about the importance of
biodiversity and ecosystem services.
Economic instruments that promote
damaging, unsustainable exploitation of biological resources (or their damage
by pollution) include subsidies, financial transfers, subsidized credit, tax
abatements, and commodity and industrial goods prices that hide environmental
and social costs. These need to be changed.
Finally, limiting global warming to well
below 2oC would have multiple co-benefits for protecting
biodiversity and ecosystem services. Care must be exercised to ensure that large-scale
land-based climate mitigation measures, e.g.,
allocating conservation lands to bioenergy crops, planting of monocultures,
hydroelectric dams) do not themselves cause serious damage to biodiversity or
other ecosystem services.
The threats to biodiversity and
ecosystem services are most urgent in South America, Africa and parts of Asia. North
America and Europe are expected to have low conversion to crops and continued
reforestation.
Table SPM.1 lays out a long set of approaches
to achieve sustainability and possible actions and pathways for achieving them.
The list is not exhaustive, but rather illustrative, using examples from the
report.
Posted by Faith Campbell
We
welcome comments that supplement or correct factual information, suggest new
approaches, or promote thoughtful consideration. We post comments that disagree
with us — but not those we judge to be not civil or inflammatory.
Photo of infested cactus at Cabo Rojo National Wildlife Refuge, Puerto Rico. Taken August 20, 2018 by Yorelyz Rodríguez-Reyes
Three and a half years ago, I blogged about the threat to columnar cacti in Puerto Rico from the Harrisia cactus mealybug. The mealybug clearly threatens the endemic cacti of the Caribbean islands, and possibly some of the hundreds of other columnar cacti growing across two million square miles of desert ecosystems that straddle the U.S.-Mexico border region.
I am pleased to report that scientists continue efforts to find biocontrol agents to reduce this insect’s damage on Caribbean islands. Much of this work is being done by the Center for Excellence in Quarantine and Invasive Species at University of Puerto Rico. The team consists of Michael West Ortiz, Yorelys Rodrígues Reyes, Ferdinand Correa and Jose Carlos Verle Rodrigues.
As of February 2019, the Center is conducting host specificity tests on a primary parasitoid of the Harrisia Cactus mealybug — Anagyrus cachamai. This wasp was found as a result of almost a decade of searching in South America and other locations. It is native to Argentina and Paraguay (Triapitsyn et al. 2018; sources listed at the end of the blog).The Center also continues surveys and studies of other primary and secondary parasitoids of the mealybug.
The work to develop a biocontrol agent for the
mealybug continues despite continuing uncertainty about the true species of the mealybug. At the time
of its discovery on Puerto Rico, the mealybug was believed to belong to a
species used as a biocontrol agent for invasive cacti in Australia and South
Africa, designated as Hypogeococcus
pungens.
However, H. pungens is now thought to
be a species complex, and the species in Puerto Rico differs from the earlier
designation (Triapitsyn et al.
2018).
Apparently
the mealybug was introduced in Puerto Rico around 2000 — probably on the ornamental common
purslane (Portulaca olerácea), an
annual succulent. (Note: the
introduction was on a host different from the vulnerable cacti.) Within five
years of the first detection in San Juan, the mealybug was sighted on cacti on
the other side of the island in the Guánica State Forest and Biosphere Reserve.
By 2010, the mealybug was widely distributed in most dry districts. Surveys
found it in all 11 municipalities surveyed in southern Puerto Rico. At some
locations, infestation levels were extremely high – e.g., 86% of stems surveyed were infested at Guánica. Infestation
rates were lower in other municipalities. As of 2010, infestations were
estimated to be present on about 1,400 km2 on the southern coast;
the rate of new infestations suggests that the mealybug was spreading rapidly
(Segarra-Carmona et al. 2010). I have been unable to obtain more recent
estimates.
The
mealybug impacts seven of 14 native cactus species occurring in dry forests of
the island, including three endemic and two endangered species in the subfamily
Cactoideae. The two endangered species are Harrisia
portoricensis and Leptocereus grantianus (USDA ARS). The tissue
damage caused by the mealybug interferes with sexual reproduction and can cause
direct mortality of the plant (Triapitsyn et
al. 2018). These
cacti provide food or shelter for endemic bats, birds, moths and other
pollinators (Segarra & Ramirez; USDA ARS). The mealybug is also now killing
native cacti on the U.S. Virgin Islands (H. Diaz-Soltero pers. comm. August
2015).
USDA Funds Conservation Efforts Despite
Apparent Absence of a Constituency Calling for Such Action
Efforts
to identify and test possible biocontrol agents targetting the Harrisia cactus
mealybug received significant funds from the Plant
Pest and Disease Management and Disaster Prevention Program. This is a
competitive grant program managed by APHIS. It is permanently funded and thus
not subject to the vagaries of annual appropriations. Until last year, this
program operated under Section
10007 of the 2014 Farm Bill. With passage of a new Farm Bill, it is now
designated as Section 7721 of the Plant Protection Act.
Since Fiscal Year 2018, APHIS has had authority to spend more than $60 million per year on this program. In Fiscal Year 2017, , the program provided $120,000 to an unspecified federal agency, $70,000 to an academic institution in Puerto Rico (presumably the Center), $15,000 to another academic institution in California, and $3,000 divided among two APHIS facilities – for a total of $208,000. The next round of funds came in FY19, when the program provided $277,267 to an unspecified federal agency to continue work on biocontrol. In addition, the program provided $78,507 to an unspecified federal agency to “safeguard[e] genetic diversity of native and listed cacti threatened by Harrisia cactus mealybug in Puerto Rico”.
No Apparent Action on
Threats to Opuntia Cacti
In my earlier blog, I also described the threat to flat-padded Opuntia (prickly pear) cacti from the cactus moth Cactoblastis cactorum. Various federal, state, and academic entities received $463,000 from the permanent fund in Fiscal Year 2016 and another $100,000 in FY2017. No cactus moth programs have received funds in more recent years.
SOURCES
Segarra-Carmona, A.E., A.
Ramirez-Lluch. No date. Hypogeococcus pungens (Hemiptera: Pseudococcidae): A
new threat to biodiversity in fragile dry tropical forests.
Segarra-Carmona,
A.E., A. Ramírez-Lluch, I. Cabrera-Asencio and A.N. Jiménez-López. 2010. FIRST REPORT OF A NEW INVASIVE MEALYBUG, THE
HARRISIA CACTUS MEALYBUG HYPOGEOCOCCUS PUNGENS (HEMIPTERA: PSEUDOCOCCIDAE). J.
Agrie. Univ. RR. 94(1-2):183-187 (2010)
Triapitsyn,
Aguirre, Logarzo, Hight, Ciomperlik, Rugman-Jones, Rodriguez. 2018. Complex of
primary and secondary parasitoids (Hymenoptera: Encyrtidae and Signiphoridae)
of Hypogeococcus spp. mealybugs (Hemiptera: Pseudococcidae) in the New World. Florida
Entomologist Volume 101, No. 3 411
USDA Agriculture Research Service, Research Project:
Biological Control of the Harrisia Cactus Mealybug, Hypogeococcus pungens
(Hemiptera:pseudococcidae) in Puerto Rico Project Number: 0211-22000-006-10
Project Type: Reimbursable
West Ortiz, M. pers. comm. February 2019
Posted
by Faith Campbell
We
welcome comments that supplement or correct factual information, suggest new
approaches, or promote thoughtful consideration. We post comments that disagree
with us — but not those we judge to be not civil or inflammatory.
a blight-resistant chestnut tree bred using traditional breeding techniques by The American Chestnut Foundation; photo by F.T. Campbell
Nearly one-third of the continental United States is covered by forests, more than 1 million square miles. As demonstrated by many authorities and – I hope! – in my blogs, these forests face increasing threats, including introduction of rising numbers of non-native insects and pathogens that kill or severely damage the tree species that comprise those forests.
One
response has been a request by the U.S. Endowment for Forestry and Communities,
the Environmental Protection Agency, and U.S. Department of Agriculture
(Agricultural Research Service, Animal and Plant Health Inspection Service,
U.S. Forest Service, and National Institute of Food and Agriculture) that the
National Academies of Sciences, Engineering, and Medicine consider the
potential for the use of biotechnology to mitigate these threats to forest
health.
The resulting report was released in January 2019 (see full citation at the end of the blog). The report is 240 pages long, very thorough, and wide-ranging. It does have a 12-page summary, listing the Panel’s many conclusions and its recommendations. While the preponderance of the report concerns forests on the North American continent, the panel did seek information about threats to endemic trees in Hawai`i, which (to my mind) are especially severe. See earlier blogs here and here.
To
me, one of the report’s most important conclusions is that while there are
multiple options for dealing with forest pests, their feasibility and success
vary widely. Saying that no single management practice is likely to be
effective by itself, the report calls
for increasing investment in the full range of strategies other than
biotechnology,i.e.,
preventing
arrival of non-native pests (recognized as the first line of defense and the
most cost-effective strategy);
site
management practices;
biocontrol;
and
enhancement
of genetic resistance naturally present in affected tree species (including developing human capital in professions related to tree
breeding).
The
panel was not asked to examine the potential for biotech to reduce threats to
forest health by altering the pests affecting North American tree species so it
does not do so.
Summarizing the
Threat
Citing
Aukema et al. 2010 and other sources,
the Academy panels reports that approximately 450 species of insects and at
least 16 species of pathogens have been introduced and have established in
continental U.S. forests. Of those, 62 insects and all of the pathogens are
determined to have a high impact. A USDA Forest Service study estimates that 81.3
million acres (about 7% of all forested or treed land in the U.S.) are at risk
of losing at least 25% of tree vegetation by 2027 due to insects and pathogens.
These pests are both non-native, introduced species and native pests that are spreading
to new regions as a result of climate change.
The
Academy panel notes that loss of a tree species can have cascading adverse
effects on the forest ecosystem and on the range of services it provides and
the values it represents to human populations.
Part A. The Technology for Trees
The
Academy panel was asked to assess the ecological, economic, and social
implications of deploying genetically engineered trees. The experts also were asked
to identify the knowledge needed to evaluate the ways such a tree might affect
the prospects for forest health. The analysis was to include social and
cultural impacts as well as impacts on forest and associated ecosystems –
including their structure, composition, processes, function, productivity, and
resilience.
This
use of biotechnology to restore healthy forests differs from applications in
industrial plantations or annual agricultural crops in that the biotech tree is
intended to proliferate in a natural forest setting.
The
authors chose four taxa — American chestnut (Castanea dentata), whitebark pine (Pinus albicaulis), ash (Fraxinus
spp.), and poplars (Populus spp.) —
to illustrate the variety of threats to forest health and efforts to date to
protect the resource.
The
committee defined forest health as:
A condition that sustains the structure,
composition, processes, function, productivity, and resilience of forest
ecosystems over time and space.
The
panel says that “forest health” is assessed based on current knowledge and is
influenced by human needs, cultural values, and land management objectives.
1. A Balanced
Analysis
The
report does not hype biotechnology for solving problems. The panel called for
research on even the foundational question: whether resistance imparted to tree
species through a genetic change will be sufficient to persist in trees that
are expected to live for decades to centuries as well as in the generations
they parent.
The
report compares the two approaches to enhancing genetic resistance to pests, i.e., selective (traditional) breeding
and relying on biotechnology. Both
involve multiple steps, expense, and risks of pursuing what ultimately turn out
to be dead ends.
Thus,
in traditional selective breeding, scientists must complete the following
steps:
1)
Determine whether genetic resistance exists within the affected tree species’
population. According to the Academy report, while many tree species have some
degree of resistance to particular native or non-native pests, finding suitable
parent trees can be difficult, and even when they are found, not all the
progeny will be resistant.
2)
Evaluate the durability of resistance in order to protect trees over decades.
3)
Propagate the resistant progeny in greenhouses or seed orchards to create
sufficient resistant genotypes for restoration and reforestation. Many tree
species are difficult to propagate using cell culture and regeneration.
In
applying biotechnology techniques, scientists must complete the following
steps:
1)
Identify the genes carrying pertinent traits – which are to be modified, introduced,
or silenced. Scientists don’t know what genetic mechanisms underlie important
traits. This discovery process is more difficult for tree species than for
agronomic crops due to the plants’ large size, long generation time, and (in
the case of conifers) immense genomes. Another problem is that forest trees
have high levels of heterozygosity due to their large population sizes and
outcrossing breeding systems, which complicates genome assembly and modification.
Still, recent technological improvements are making this identification process
easier.
2)
Insert the genes using various biotechnology tools such as transgenesis and
genome editing.
3)
Produce trees containing the desired gene sequence to
regenerate plants from disorganized callus tissue. As noted above, many tree species
are difficult to propagate using cell culture and regeneration. Even when this
approach is possible, the regeneration of a plant from a single cell may not
produce an individual that has the desired genetic change in every cell.
The
time line for applying either approach to protect forest health will depend on several
factors, including the biology of both the tree and the pest, and the
environments in which the target tree species exists. It can vary from a few
years to multiple decades.
2. Who Should
Carry Out Genetic Improvement of Trees (and by implication, all long-term
strategies to protect forest health)?
Trees
provide private as well as public benefits, such as income from timber sales. However,
the costs of developing a genetically resistant tree – whether achieved through
traditional breeding or biotechnology processes – will be incurred up front and
the benefits will follow later – often decades or even centuries later. Consequently,
the sponsors need a long time horizon!
The
panel suggests that the public sector can have greater patience when it
perceives that significant public benefits will be forthcoming. The private
sector is not likely to invest in the protection of forest health because it
cannot fully capture the benefits that may accrue. The authors define “public
sector” to include government agencies and non-profit organizations.
Part B. Impacts, Ethics, and Policy
1. Impacts
The
report provides careful analysis of the ecological impacts that should be
considered in evaluating the use of biotechnology to maintain or improve forest
health. The report emphasizes that if the modified trees are to spread and
restore the species to its role in the ecosystem, the modified trees must be
competitive in the ecosystem (while not being invasive!). The trees must be suited
to the variety of climates and other biophysical conditions found throughout
the tree species’ range. The report even said that establishing the rangewide
patterns of distribution of the target species’ natural standing genetic variation
should be researched before a project is begun aimed at inserting pest
resistance genes.
2. Public
attitudes and ethical considerations
The
panel was charged to consider social, cultural, and ethical issues related to
the potential use of biotechnology to develop trees resistant to pests. They
devote 13 pages to examining this complex set of issues, which range from
Native Americans’ use of black ash to concepts of “wildness” and competing
models of “conservation”. There have
been few surveys or other studies of Americans’ attitudes. The panel also notes
that the public lacks in-depth knowledge about genetic interventions and processes,
so their attitudes are likely to change — for or against use of the technology
— as they learn more or associate biotech with strongly held beliefs.
The
Panel notes that important ethical questions fall outside any current “impact
analysis” evaluation system, or any new analysis that focuses on “ecosystem
services”. It calls for additional research
on societal response to biotechnology applied to forest health and development
of new forms of engaging full range of stakeholders.
3. Need for a New
Impact Assessment Framework
The panel
concludes that the current regulatory system does not provide for consideration
of most aspects of forest health in assessing the safety of a tree developed
through biotechnology, including those described above. Consequently, the
panel calls for an entirely new assessment process in order to evaluate both
the ecological and social/ethical considerations.
The
long-standing Coordinated Framework for the Regulation of Biotechnology relies
on existing federal statutes. Under this system, the regulatory agencies (USDA Animal
and Plant Health Inspection Service, Environmental Protection Agency, sometimes
Food and Drug Administration) regulate specific products, not the process by
which the products are produced. For example, USDA regulates only the small
subset of biotech trees which were transformed via use of a bacterium, Agrobacterium tumefaciens, to insert the
desired trait.
The
panel says that an agency undertaking an environmental analysis under the terms
of the National Environmental Protection Act would need to add an analysis of
some components of forest health.
To rectify these analytical gaps, the panel suggests creation of an integrated impact assessment framework that combines ecological risk assessment with consideration of ecosystem services. This integrated framework would evaluate the effect of the pest threat – and responses to that threat – on forest processes –as well as on associated cultural and spiritual values. The impact assessment must make explicit the links between specific forest protections and their effects on important ecosystem services. The panel points to an EPA guidance document on economic impact analysis (see reference at the end of this blog) as a useful starting point. The panel suggests that this framework should be used to evaluate any forest health intervention, including use of selectively bred trees.
Because
of the length of time until tree reproductive maturity and long life span of
most trees, collecting data for an impact assessment might take years. The
panel suggests adopting a tiered system which would allow field trials of low-risk
transgenic trees to reach flowering stage so as to provide data on gene flow
and climatic tolerances – data that are essential for a proper impact
assessment that would evaluate the likelihood of ultimate success of the
restoration effort. Such experiments and
carefully developed models must also identify sources of uncertainty.
Adoption
of such a stepwise, iterative process
requires abandonment of the current regulatory system, which does not permit
the flowering of biotech trees in most cases.
My Conclusions
The
report makes clear several realities:
1)
the magnitude of the threat to our forests from non-native pests – which
warrants an effective response;
2)
the strengths and weaknesses of the several response strategies – none of which
can solve this problem in isolation;
3)
the scientific challenges that need to be overcome to apply strategies aimed at
enhancing tree species’ genetic resistance to pests;
4)
the need for greatly expanded programs to implement the various strategies.
Also, the report shows how unprepared our country is to systematically assess the full impacts of new forms of tree breeding and forest health. To rectify this gap, the report also calls for a complete overhaul of the procedures by which the government currently evaluates the environmental risks associated with applying one of the strategies, genetic transformation of the plant host – which is defined (in the Glosssary) as including transgenesis, cisgenesis, RNA interference, genome editing, and insertion of synthetic DNA.
The
recommended actions in this report – taken either individually or collectively
– require a level of commitment by government and conservation organizations
that far exceeds the current level.
I
hope the Academies’ prestige can prompt such commitment. For example,
development of a sufficiently robust coalition of groups could re-invigorate
our society’s response to the invasive pest threat. The report has received
some encouraging attention. It was reported in Nature and Scientific
American. About 130 people tuned in live to
the launch webinar on January 8th. So far, almost 1,200 people have
downloaded the report.
The
government shutdown has delayed the sponsoring agencies’ (USDA and EPA) official reactions to the report. It probably curtailed
some publicity efforts among all the sponsoring agencies. Also, the report will
be only one item in the overflowing inboxes of agency scientists and managers
after 35 days on furlough. I hope it won’t be lost, especially with the threat
of a second shut-down.
How
can those of us in the public who care about our forests ramp up our activity to
support these recommendations?
A reminder: Scott Schlarbaum and I addressed the need for a greatly expanded restoration component as part of a comprehensive response to non-native tree-killing pests in our report Fading Forests III, released five years ago. It is available here.
SOURCES
Aukema, J.E., D.G.
McCullough, B. Von Holle, A.M. Liebhold, K. Britton, & S.J. Frankel. 2010.
Historical Accumulation of Nonindigenous Forest Pests in the Continental United
States. Bioscience. December 2010 /
Vol. 60 No. 11
National
Academies of Sciences, Engineering, and Medicine. 2019. Forest Health and
Biotech: Possibilities and Considerations. Washington, DC: The National
Academies Press. doi: https://doi.org/10.17226/25221.
U.S.
Environmental Protection Agency. 2014. Guidelines for Preparing Economic
Analyses. Washington, D.C.
