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SOUTHERN APPALACHIAN BIOLOGICAL CONTROL INITIATIVE WORKSHOP
The North Carolina Arboretum, Asheville, NC
September 2627, 1996
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A Southern Appalachian Biological Control Initiative workshop
was held at the North Carolina Arboretum near Asheville, North
Carolina, on September 2627, 1996 (enclosures 1 & 2).
The workshop was sponsored by the National Biological Service
(Biological Resources Division) and the Southern Appalachian Man
and the Biosphere (SAMAB) Program, with funding assistance from
the National Biological Control Institute. A funding limit of
$200,000 has been provided for conducting the initiative. The
work is to be carried out on Department of Interior lands in the
southern Appalachians though it is recognized that pests do not
recognize political boundaries.
The most serious pest problems that confront park managers in
the southern Appalachians are exotic pests introduced from outside
of North America. These include insect, disease, and weed species.
The Department of Interior does not presently have a comprehensive
strategy to identify, prioritize, and manage exotic pests on department
lands. However, National Park Service policies promote the use
of biological control methods, if any exist, in preference to
chemical control techniques in most situations.
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This workshop was therefore organized to accomplish several objectives:
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To accomplish these goals, the workshop was organized into two
sections. The first day was devoted to invited presentations on
biological control including a discussion of concepts, practices,
and requirements of biocontrol.
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Ernest S. Delfosse, Nationa1 Biological Control Institute, presented
his thoughts on (1) definitions, principles, and bases, (2) strategies
of pest management, (3) types of biological control, (4) targets
and agents, (5) anthropods vs. plants, antagonists and competitors,
(6) steps in a classical biological control program, (7) host
specificity testing, (8) environmental risk assessment, and (9)
postrelease monitoring.
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Roy G. van Driesche, Department of Entomology, University of Massachusetts,
then discussed the biological control of anthropod pests of the
northeastern and northcentral forests of the United States. He
also identified opportunities for future biocontrol. In a report
to be published soon, he identified 94 species of forest anthropods,
58 of which are believed to be native to North America. Twenty
nine species are exotics. Detailed recommendations for biological
control of these pests were outlined in the report. The details
of biological control were grouped into several categories as
follows: (1) natural enemy introductions, (2) augmentation of
natural enemies through artificial propagation and release, (3)
studies or population dynamics to clarify the importance of natural
enemies or identify modifications of silvicultural practices to
enhance the effects of existing natural enemies at production
sites, and (4) no role for biological control.
Van Driesche stated that 27 exotic pests lend themselves to control
via natural enemy introductions. Fourteen species were identified
for which studies of augmentative biological control seemed useful.
A need for population dynamics studies was identified for 17 species.
For 29 species, there appeared to be no opportunity for biological
control.
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Gary Johnston, National Park Service, discussed concerns and opportunities
for biological control in national parks. He acknowledged that
it was well known that exotic pests present in this country generally
became established without their natural enemies. Opportunities
to undertake biocontrol programs will be limited by the availability
of funds and policy constraints though there is support for biocontrol
efforts where there are opportunities for success. Gary enumerated
severa1 concerns of park managers including (1) the fact that
exotic pests have become established and are causing perceptible
damage. (2) the feeling that exotic pests should be eliminated
rather than reduced and held at acceptable levels, (3) the question
as to whether biocontrol agents are or could be effective, (4)
conflicts between policies and practices, (5) a concern about
possible side effects of introducing biocontrol agents, (6) the
feasibility of accomplishing areawide vs. localized success combined
with direct control where desired, and (7) the possibility of
"upsetting the balance of nature."
On the positive side, Gary thinks there are opportunities for
using or enhancing biological control. These could take the form
of (1) setting up longterm study sites on park lands, (2)
taking steps to expand our biological understanding of biocontrol
agents and/or exotic pest populations working through the Biological
Resources Division of USGS (formerly NBS), (3) seeking and capitalizing
on opportunities for expanded environmenca1 education for park
visitors and at nearby educational institutions, (4) interacting
with a APHIS biocontrol advisory group, and (5) getting assistance
or advice from the National Biological Control Institute in effectively
applying biological controls .
Gary said that the NPs views biocontrol as a very useful approach,
sees it as an opportunity for environmental education, and considers
biocontrol. where it is effective, a valuable alternative to chemical
control.
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Randy Westbrooks, USDAAPHIS, and Faith Campbell, National
Associatior1 of Exotic Pest Plants Councils, presented an overview
of biological invasion and strategies to prevent the world movement
of weeds. Randy made several important points:
Randy identified examples of several problems that have received
serious consideration: Kudzu, purple loosestrife, mellaluca. and
the biomagnification of pesticides in the food chain.
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Faith Campbell pointed to the invasion of exotic plants in natural
areas in the southern Appalachians (enclosures 4 and 5). This
is significant in terms of the acreage involved, the number of
species involved, and the resulting threat to other natural resources.
She went on to state that invading exotics are not getting the
attention in the Appalachians that is being given to them in other
region8. Some or the perceptions of pest impacts are effected
by changes in soil characteristics, changes in susceptibility
to fire, and a lack of understanding of pest impacts on wildlife
foods and other illy defined economic impact3.
Faith went on to describe what is being done to combat exotic
plant pests. This included mechanical removal, use of herbicides,
and consideration of promising biocontrol resources. She felt
that if biocontrol efforts are to receive adequate attention,
several things must happenwe must have political support,
an adequate environmental education effort, and information sharing/
networking between affected agencies.
Faith indicated that an interagency committee is now working to
develop improved strategies and better coordination of effort
for dealing with invasive species. There is a similar ongoing
international effort.
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The morning's speakers then led a panel discussion on biological
control. Some highlights included:
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Scott Schlarbaum, OTKnoxville, moderated the afternoon session.
He set the stage by presenting a brief, illustrated overview entitled
"Troubles in paradise . . . decline of southern Appalachian
forests." It covered the problems of chestnut blight, dogwood
anthrachnose, beech bark disease, butternut canker, hemlock wooly
adelgid, gypsy moth, balsam woolly adelgid, oak decline, pear
thrips, and exotic plant pests. He then introduced the speakers
who dealt with specific exotic pests, their status and spread,
the use of and needs for biocontrol, and related information.
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Bill MacDonald, University of West Virginia, discussed chestnut
and chestnut blight. He indicated that many people in several
organizations are working on chestnut and are optimistic that
a resistant hybrid will soon be available for outplanting.
Bill pointed out that prior to the blight, chestnut was a major
tree species in the Appalachians and was highly prized for its
lumber and other wood products. When the blight was introduced
from Japan, it quickly spread throughout the range of the species
killing every tree. Today, all that remain are clumps of sprouts
that never reach maturity.
Research on chestnut has focused on breeding. Early work was done
improperly. More recently, backcrossing efforts, largely carried
out by the Chestnut Foundation, have resulted in the development
of blightresistant trees.
Another approach has dealt with hypervirulence. This phenomenon
was first discovered in Italy in the 1970's and revealed a new
class of viruses. Since then, it has been determined that the
viruses in Michigan and Italy are different. Some success in treating
chestnut trees in the U.S. has been achieved but problems remain.
In Wisconsin, use of the Michigan virus has yielded promising
results.
A third approach involving microbiology has produced encouraging
results, too.
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Mark Windham, UTKnoxville, discussed the dogwood anthracnose.
He briefly summarized its history of development in the Northeast
and Pacific Northwest. The disease was found near Crossnore, NC,
in 1986 and has since spread throughout western North Carolina.
Dogwood anthracnose has also been found in Ireland, Great Britain,
and may be in ports of Europe.
Mark pointed out that the disease conidia are built for survival
and are able to resist dessication. Dispersal is thought to be
associated with insects and splashing rain. Proximity to water,
elevation, and aspect all seem to be related to the occurrence
of the disease.
At present, it is not known how resistance is inherited. Other
dogwood species are moderately to very resistant to the disease.
Breeding is going on using material from such trees as the Presidential
tree at Camp David, MD, in hopes of developing resistant flowering
dogwood,
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David Houstin, USDAForest Service retired, discussed the
beach bark disease which involves beech, the beech scale, and
a nectria fungus. He described the factors influencing the establishment
and distribution of the disease and "factors contributing
to the abundance of beech.
In talking about the disease, he covered the causel complex, fungus
bark pathogens, and forest structure features.
The disease was first discovered in the Great Smoky Mountains
National Park in 1993. It now occurs throughout the natural range
of beech. Up to 85 percent of the Larger beech trees are dying
or dead. .
Several factors influence the causel complexpathogens
of nectria, pathogens of the scale, and predators of the scale.
There ore no known parasites of the scale .
There is evidence that some beech trees are resistant to the pest
complex. In the Maritimes, the bark of beech is often covered
with a protective layer of lichen. This does not favor the scale.
Some larger trees have been found in Maine and West Virginia that
seem to be unaffected by the pest complex. These phenomenon suggest
that there may be genetic resistance to the pests. Research is
now being aimed at two approaches: (1) determining what kind of
management system might be needed to favor resistant trees, and
(2) vegetatively reproducing material from apparently resistant
trees and reintroducing them into the forest. So far, the latter
approach has been blocked by a problem with vegetative propagation.
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Bob Anderson, USDAForest Service, discussed butternut canker.
He started by describing effects on the hostmultiple annual
cankers on branches and seems. Callusing occurs around these cankers.
Top dieback follows the fungus as it progresses up the tree,
He pointed out that butternut is distributed throughout the eastern
U.S. and that the disease was apparently first introduced in the
Southeast . Up to 80 percent of the larger trees have died in
some states.
Fungal infection starts in the lower crown, then moves upward.
Spores flow down to the lower trunk and branches. Cankers become
perennial. All life stages (seedling to mature tree) are affected.
Nuts are also infected.
The disease is spread by rain splash and insects.
In the southern Appalachians, 77 percent of the butternut have
died from the disease. This has occurred over a 20year period.
All butternut on the Great Smoky Mountains National Park are infected.
In the southern Appalachian, it has been noted that many surviving
trees are recovering. Cankers are callusing over. Top dieback
is disappearing. There are fewer cankers on more recentlyinfected
trees. This may reflect genetic resistance.
Assuming that there is some form of resistance, material has been
taken from a few trees, some that are canker free, for propagation.
Already problems are being encountered in the propagation work.
With regard to biological control, Bob feels that several things
need to be done--determine if the fungus occurs elsewhere in the
world, figure out why some trees in the U.S. are recovering, and
pursue the genetics work.
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Mike Montgomery, USDAForest service, discussed the hemlock
wooly adelgid. He first reviewed the history, biology, and control
of the pest. It is distributed from Massachusetts to northwestern
North Carolina. Its distribution is probably limited by its cold
hardiness. The adelgid was first discovered in Richmond, VA, in
1954. It was found killing hemlock in Connecticut in the 1980's.
The pest is currently causing hemlock decline in the Great Smoky
Mountain and Shenendoah National Parks.
Regarding biological control, the adelgid has no known parasites
in the U.S. Searches in hemlock forests in the Orient have revealed
a guild of predators feeding on the adelgid there. Efforts are
being made to find native predators in the U.S. These have included
studies of the phenology of a coccinillid predator and the adelgid
in Connecticut. Studies are also underway to determine the physiological
host range of potential predators.
A Japanese mite has been introduced that feeds on the wax surrounding
the adelgid. This causes dessication of the adelgid. However,
there are some problems in carrying out this work.
Introduction of a Japanese coccinellid has yielded promising results
However, searches continue for other promising predators of the
hemlock woolly adelgid in the Orient.
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Dick Reardon, USDAForest Service, discussed the gypsy moth
(GM). He reviewed the habits of the insect, its distribution and
damage since l9O0, suppression efforts that have been pursued
over the years, and the history of biocontrol over time.
Numerous parasites and predators have been introduced over the
years, but few have been highly successful. Rearing and establishment
problems have been encountered all along the way. As experience
has been gained, control strategies have changed.
Dick provided a list of exotic parasites, predators, and pathogens
that were used against the gypsy moth from 1904198O. Out
of all this the nucleopolyhedral virus (NPV) and the fungus Entomophaga
meimaiga have been very
effective. The virus has been most effective in high density GM
populations. The fungus is very effective in low density populations
and is the most effective agent of all.
Two established exotic parasites look quite promising. Exploration
is continuing in the Far East to find additional species.
Other established exotic natural enemies have been partially but
variably effective.
Dick indicated that 1996 was a good year for pathogens, a poor
one for parasites and predators. The level of GM defoliation was
generally down. Once GM populations begin to increase, he has
little confidence that parasites and predators will have a significant
effect. He also stated that we need to be sensitive to the possible
threat of pathogens in areas with threatened and endangered species.
Further, he acknowledged that much yet remains to be learned about
the effectiveness of biocontrol agents under a variety of conditions
over time.
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On the second day, workshop participants were divided into six
discussion groups (enclosure 5). Each group had a mixture of land
managers from different agencies and technical experts in biological
control. Their task was to identify and rank exotic pests first
on the basis of their threat to natural forest resources and secondly
to prioritize these pests as to the likelihood of being able to
demonstrate successful biocontrol using available technology and
within the limits of time and money.
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The group rankings of exotic insect, disease, and weed species
as to their threat to natural forest resources is summarized in
Table 1.
Table 1.Individual group ranking of threat of exotic
pests.
| Exotic Pest | ||||||
| Balsam woolly adelgid | ||||||
| Hemlock wooly adelgid | ||||||
| Beech bark disease | ||||||
| Butternut canker | ||||||
| Dogwood anthracnose | ||||||
| Chestnut blight | ||||||
| Oriental bittersweet | ||||||
| Garlic mustard | ||||||
| Gypsy moth | ||||||
| Microstegium | ||||||
| European sawfly | ||||||
| Kudzu | ||||||
| Japanese brome grass | ||||||
| Chinese yam | ||||||
| Tree of heaven | ||||||
1/ Ppolitically sensitive. Much attention has been
given to this exotic weed.
Other insects, diseases, and weeds were considered by the representative
groups but were not ranked for a number of reasons. As a matter
of record. the insects, diseases, and weeds discussed by one or
more groups included:
| Insects Asiatic oak weevil Balsam woolly adelgid Beech scale Chestnut gall wasp European sawfly Gypsy moth Hemlock woolly adelgid Pear thrips | Diseases
Beech bark disease butternut canker Chestnut blight Dutch elm disease White pine blister rust |
| Weeds Autumn olive Chinese yam or cinnamon vine Exotic honeysuckle Garlic mustard Japanese brome grass Japanese knotweed Japanese stilt grass or Nepal grass Johnsongrass Kudzu Mile aminute Mimosa or silk tree | Weeds (continued) Multiflora rose or baby rose Oak decline Oak wilt Oriental bittersweet Princess tree or empress tree Privet s Spotted knapweed Thistles Tree of heaven or stinktree
Tropical soda apple |
It should be noted that several pests received equal ranking within
three of the groups. This was based on the feeling that two or
three pests were similar in their threat to the respective forest
resources. In one group, insects and diseases were ranked separately
from weeds. However, it should be noted that there was unanimous
agreement that hemlock wooly adelgid should be ranked number one.
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Considerable discussion followed in seeking to reach a consensus
on which exotic pest(s) should receive emphasis in meeting a
biocontrol effort on park lands. Highlights of this discussion
were as follow:
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The thought was expressed that what works for one adelgid might
work for the other. This could justify looking at both adelgid
problems. Mike Montgomery said that we should exercise caution
in taking this approach since there are differences in the phenology
and niches occupied by the respective insects.
Mike reiterated that considerable effort has been exerted and
will continue, resources permitting, to find promising biological
control agents for the hemlock woolly adelgid in its native habitat
in the Orient.
Dick Beardon indicated that they are expending $130,000 $140,000 per year to find biocontrol agents for the HWA, Perhaps this work could be tied in or coordinated with any effort in the Southern Appalachians .
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Kudzu
Larry Barber reviewed his recent proposal to suppress Kudzu through
augmentative releases of parasitized soybean loopers (enclosure
6). He indicated that he and others found extensive defoliation
of Kudzu near Union, SC, in September 1995. It was determined.
that the damage was due to the soybean looper and the velvetbren
caterpillar. It has therefore been proposed that soybean caterpillars
parasitized by an egglarval wasp (Copidosoma truncatellum
(Dalman)) be released on study sites occupied by Kudzu on
the Great Smoky Mountain National Park. The parasitizacion of
the soybean caterpillar prevents the looper from reaching the
adult stage while increasing the amount of defoliation inflicted
significantly. This would seem to offer an alternative for the
use of toxic herbicides to control Kudzu.
Ernest Delfosse described some of their biocontrol work with the
soybean looper in other areas.
Keith Langdon talked about some of the work they have done on
Kudzu on the Great Smoky Mountains National Park.
Roy Van Driesche agreed that Kudzu was probably a good target
for biological control. However, he cautioned that it might not
be wise to pursue an augmentative approach on a politically sensitive
pest species. Also, it is likely that results from such an approach
on Kudzu might only apply in localized areas. Perhaps an approach
could be developed which use both the augmentative approach and
the use of herbicides on different sites. Finally, he said he
would favor selecting an exotic pest and applying the classical
biological control approach.
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Some conferees saw the wisdom of undertaking a limited effort
on a politically sensitive pest with a view toward leveraging
additional support it the effort was successful.
Mike Montgomery and Ernest Delfosse asked whether there were facilities
to handle biological control agents in North Carolina. The answer
was that modern quarantine facilities are available in Raleigh.
Roy pointed out that one must have a combination of impact, leverage,
and momentum to get a biocontrol project accomplished.
Mike stated that a group is being formed to identify and push
for support for needed pest management research and applications
in the eastern U.S.
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The Forest Service Forest Health staff showed an outstanding video
entitled "Hemlock at Risk." This was a collaborative
effort between Forest Service Regions 8 and 9. Copies of the video
were provided to interested viewers in the room.
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Chuck Parker, NBS, next directed the discussion to prioritizing
the exotic pests that should be the focus on biological control
efforts on Park Service lands. A number of concerns or questions
surfaced right away :
Severa1 observations were made that would provide reasons for
including or excluding exotic pests on a priority list for a biological
control project:
There are no sawtimber size chestnut trees in the forest, only
sprout clumps that eventually die. However, a lot of work has
been done to develop resistant chestnut trees. This should provide
encouragement for an expanded breeding program and outplanting
under forest conditions.
There are a large number of living hemlocks in the range of these
species in the eastern U.S. Many of these trees are not yet infected
but they are threatened.
In the case of the HWA problem, what would $200,000 buy? Mike
said that we should be able to identify and introduce at least
two parasites, evaluate predators that may already be in the area,
and learn more about the biology and ecology of the HWA.
Predators have been introduced in BWAinfested Fraser fir
stands on Mt. Mitchell, NC. Perhaps any successes there can be
duplicated in HWAinfected hemlock stands. Again. though.
the two pests occur on different portions of different host trees,
have different biologies, and occur on different sites and in
different environments.
Some discussion centered on doing limited work on Kudzu and chestnut,
two politically sensitive species while focusing primarily on
another pest. In response to the question, approximately $10,000/year
for 2 years would lead to the identification of promising parasites
and predators of Kudzu. For chestnut, a like amount would be needed
for hypovirulence and outplanting/monitoring work, the latter
on NPS lands. Work on these two species could probably be used
to attract additional outside monies.
It was urged that a carefully orchestrated educational effort
be mounted, preferably using funds from SAMAB.
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The conferees summarized their opinions on several exotic pests as
follows
| Hemlock woolly adelgid | Exists; far along | Cautiously optimistic |
| Balsam woolly adelgid | Slow | ? |
| Beech bark disease | Exists; known difficulty | Fair |
| Kudzu | Easily | Good; involves time and cost for screening |
| Butternut canker | Exists; far along | Not classical biological control |
| Dogwood anthracnose | Exists | Not classical biological control |
| Chestnut blight | Exists; far along | Optimistic; cautious on hypervirulence |
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Table 2.--Summary or biologica1 control project recommendations
for the National Park Service.
| Action | Exotic Pest | Recommended Funding |
| 1st priority | Hemlock woolly adelgid | |
| 2nd priority | Kudzu | |
| 3rd priority | Chestnut blight | |
| Educational effort | ||
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