Both programs provide funding for research and education projects
that promote environmentally sound, economically viable and
socially acceptable agriculture.
SARE receives its funding from the United States Department of
Agriculture. ACE is a joint initiative of the USDA and the United
States Environmental Protection Agency.
The Northeast Region includes: Conn., Del., Maine, Md., Mass.,
N.H., N.J., N.Y., Pa., R.I., Vt., W.Va.,and Washington D.C.
This issue highlights four projects that are testing ways to cut
pesticide use in fruit, vegetable and ornamental plant production
systems.
In this issue:
"Living Lab Tests Alternatives for Vegetable Production"
"A Common Sense Approach to Cutting Pesticides in Apple
Production"
"A Grower's View (on Scab-Resistant Apple Varieties)"
"Seeding Sustainable Landscapes"
"Swapping Sprays for Spores"
Print copies of Innovations can be obtained by writing
Innovations,
NE SARE, Hills Building, UVM, Burlington, VT 05405-0082 or
calling
802-656-0471.
Additional information about these an other SARE and ACE projects
can be obtained by writing Beth Holtzman, at the address above,
or at bholtzma@moose.uvm.edu or by calling 802-656-0554.
Alternate Vegetable Systems Tested in New Living Lab
Early results from a long-term, multi-disciplinary Penn
State University project are providing valuable information for
vegetable growers who want to cut their pesticide use.
In a cabbage experiment, for example, a living mulch of
annual ryegrass between cabbage rows provided better early weed
control in first year trials than pre-transplant herbicides,
flaming or mowing weeds.
These findings are important, says project coordinator
Kenneth Steffen, because intensively managed vegetable crops are
high per-acre users of agrichemicals. Steffen is an assistant
professor of vegetable crop physiology at Penn State.
"Much of the current public dialogue over the sustainability
of agriculture is taking place in the absence of information on
the relative ecological, agricultural and economic viability of
alternative production systems," Steffen explains.
"Information that is available on alternative vegetable
production systems, in particular, is extremely limited with
almost no data comparing alternative and conventional systems in
replicated tests," he says.
To fill that gap, Steffen is collaborating with a diverse
group of Penn State researchers and Pennsylvania growers in an
ambitious SARE-funded project. Their goal is to develop and test
production practices and systems that are more resource
efficient, more profitable and more environmentally sound.
Five different production systems are being evaluated in
replicated tests for their ecological, agricultural and economic
performance. The production systems range from certified organic
to conventional soil and pest management practices. Most of the
work is being done on a 12-acre research site Steffen calls a
"living laboratory/classroom."
The researchers are using realistic, farm-scale operations
to manage the different production systems, or "farms," on the
research site. Each "farm" grows four to five vegetable crops in
a given season as part of an intensive four-year rotation.
Overseeded living mulches and green manure crops are included in
some of the systems.
At the same time, researchers are collecting detailed
baseline data on each of system so that they can try to determine
which factors and interactions are important in the performance
of each system.
Living Mulches Beat Herbicides
In the cabbage studies, a living mulch of annual ryegrass
between cabbage rows provided the most effective weed
suppression,followed pre-transplant herbicides, flaming at the
two- to four-leaf stage of growth with a propane gas burner, and
mowing vegetative growth several times during the growing season.
"We found the greatest plant vigor in the herbicide and
living mulch treatments, followed by mowing and then flaming,"
says Horticulture Professor Michael Orzolek, who directed the
studies. Additionally, reports Orzolek, there was no apparent
reduction in cabbage growth from rye establishment.
But the researchers also noted other important interactions.
"While the living mulch was effective against lambsquarter
and red-root pigweed (the two most prevalent weeds in the weedy
check plot) it would not suppress the growth of perennial weeds
such as Canada thistle or horseradish," Orzolek says. Also,
researchers found, the flaming for weed management had the
additional benefit of controlling flea beetles.
This initial work, says Orzolek, is significant because it
shows the potential of alternate management strategies for a
prime production problem: weeds.
Early weed infestation is a crucial grower concern because
it reduces both early and total marketable yield and quality.
Also, weeds can serve as reservoirs for insect and disease
organisms, especially viruses. In fact, surveys of organic
growers in the United States and Europe indicate that weeds are
their primary production problem.
Conventional growers rely heavily on herbicides for weed
control. But, says Orzolek, vegetable crops are considered minor
crops by pesticide manufacturers, and a number of crops have few
or no herbicides labeled for weed control during the season.
"Clearly, alternatives to synthetic herbicides would benefit
a wide range of growers," he says.
Alternatives for Early Blight
The research team is screening a number of alternative
materials, including selected plant extracts, antagonistic
bacteria, hydrogen peroxide and bicarbonate for their efficacy in
the control of early blight in tomato.
The goal is to gain a better understanding of the effect of
these compounds on the natural ecosystem of plant surfaces.
Because some of the compounds are usually considered innocuous,
factors other than chemical toxicity are being investigated.
"A better understanding of leaf surface ecology may provide
us with some effective biocontrol methods for vegetable foliar
diseases," explains Plant Pathology Professor Felix Lukezic, who
is leading these studies.
One possibility, he says, is that certain germicidal
compounds alter or eliminate the natural microbiological
population, and that the bacteria and/or yeasts which move in are
antagonistic to the pathogens. The team is testing this
hypothesis using an antibiotic-resistant labeled antagonist
bacterium to monitor changes in the leaf surface ecosystem.
Refining Insect Control Techniques
Insect pests are targeted in several portions of the
project.
For example, in tomatoes and snap beans, predators (pre-fed
early instar Chysoperla larvae) are being hand released to
control aphids. Natural enemies are being obtained under
commercial conditions, and economic data are being compiled.
Also in tomatoes, project participants were able to control
an early immigration of Colorado potato beetle using adulticides
(rotenone or esfenvalerate) followed by a well-timed spray of
microbial pathogen in both conventional and ecologically-oriented
plots.
"This demonstration of the importance of proper timing with
the microbial material is relevant to all grower audiences," says
Assistant Entomology Professor Shelby Fleischer, who is
coordinating the insect studies.
In still other studies, the team is testing alternative
strategies for European corn borers and cucumber beetles.
"Integrated pest management (IPM) programs for vegetables
will be more complex than those in use with field crops,"
Fleischer predicts. "They will require all the parameters used
with field crops, but will also need to be modified by factors
such as nutrient value, consumer acceptance, storage loss, etc."
Fleischer also notes that much additional information still
needs to be generated.
"While many of our observations are preliminary, these
studies are beginning to offer some insight into possibilities
for a more biorational pest control strategy in high-value food
crops," he says.
A Commonsense Approach to Reducing Pesticides in Apple Production
Editor's note: Since 1988, an interdisciplinary team from Cornell
University, Rodale Institute, Rutgers University, University of
Massachusetts and University of Vermont have collaborated in an
effort to develop sustainable apple production systems for the
Northeast. More than two dozen researchers, Extension specialist
and growers are participating in the project, which was expanded
recently to include personnel from The Pennsylvania State
University. It has received support from both the SARE and ACE
Programs. The following article focuses on aspects of the project
most directly related to reducing pesticide use in apple
production.
By Terry M. Schettini
Rodale Institute
Due to the large number of pests that plague apples in the
Northeast, commercial apple production is relatively chemical
intensive. In a given season, commercial growers may make 12 or
more applications of pesticides to control various pests.
Our research, however, is showing that by using
disease-resistant cultivars and advanced integrated pest
management (IPM) strategies, growers can significantly decrease
their pesticide use while remaining economically competitive.
Scab-Resistant Cultivars
A major focus of our pesticide-reduction work has been
developing sustainable production systems for cultivars that have
genetic resistance to apple scab, a devastating fungal disease
that can make apples unfit for the fresh market.
For conventional varieties, scab control is achieved through
the use of fungicides. Two of the most common fungicides, Captan
and EBDC's, are either known or suspected of causing human health
problems such as cancer and birth defects.
Genetic resistance to apple scab, however, eliminates the
main reason to spray fungicides during the spring and early
summer in the Northeast, and thus can eliminate between three and
four sprays a year.
Since many of the scab-resistant cultivars are also
resistant or tolerant to other diseases, such as powdery mildew,
cedar apple rust, quince rust, and fire blight, they provide
promise for reducing the need for pesticides even further. In
western New York, for example, researchers have been able to
reduce fungicide applications by seven or eight sprays a year.
This potential reduction in the need for fungicides (for
diseases other than scab) depends on the disease pressure in the
area as well as the particular resistance of the cultivar.
Therefore, until further information is available, we're advising
growers to avoid planting scab-resistant cultivars near apple
trees that are susceptible to powdery mildew or near cedar trees.
Still, the potential for reducing fungicide use is
significant. If scab-resistant cultivars can be used to eliminate
chemical control of this disease, and they are widely adopted by
growers in the region, orchardists could save millions of dollars
in pesticide use and prevent millions of pounds of fungicide from
being released into the environment each year.
In 1991 for example, New York growers applied approximately
23 pounds of fungicide per acre and spent approximately $103 per
acre for scab control. Those applications, if consistent over the
68,000 acres of apples grown in New York, translate to roughly
1.5 million pounds of fungicide at an annual cost of $7 million.
Given the potential savings, why do scab-resistant cultivars
account for less than 1 percent of apple acreage in the region?
There are several reasons. Since it can take up to 10 years
before crop sales from new trees equal the cost of establishing
and maintaining them, growers are reluctant to replace well-known
varieties, such as Red Delicious and McIntosh, with new
varieties. Even so, many growers are putting in small blocks of
scab-resistant cultivars now to test their success.
Finally, additional information is needed about producing
and marketing scab-resistant cultivars. Even though the most
recent scab-resistant cultivars hold up well to scab pressure,
recent reports of scab development on some earlier cultivars
underscores the need for comprehensive pest management programs.
In other words, to get the most from scab-resistant cultivars we
need to develop and implement a regional management strategy, as
used in other crops, and to continue developing integrated
strategies that incorporate both genetic and non-genetic control
techniques for apple scab.
Other Fungal Diseases
Furthermore, we will still need to deal with the minor or
"summer" diseases, since many apple scab fungicides incidentally
control diseases such as sooty blotch, fly speck, black rot,
white rot, bitter rot, and Brook's spot. These diseases may
become problematic in warmer, humid regions or during unusually
humid summers.
One approach under investigation includes techniques which
increase air circulation and reduce humidity in the tree canopy.
In studies so far, summer pruning did reduce incidence of
flyspeck, but lowering tree-planting density or closely mowing
orchard ground cover had no impact on the incidence of sooty
blotch or flyspeck.
Advanced IPM
Advanced IPM programs, such as the "second-level" IPM
programs under development in Massachusetts and similar programs
elsewhere, integrate the use of genetic, cultural, biological and
least-toxic chemical methods of controlling pests. One such
program resulted in 30 percent reduction in "dosage equivalents"
of insecticide and miticide being applied in the orchard, and 18
percent fewer spray events than with standard IPM.
In New Jersey, for example, a program of three to four
sprays later in the season can control sooty blotch and flyspeck
on scab-resistant cultivars. In contrast, a program of seven or
more sprays must be started in the spring to control scab and
other diseases on standard cultivars. Eliminating early season
fungicides allows beneficial mite predator populations to grow.
But even a reduced-spray program can disrupt bio-control of pest
mites. To overcome this problem, alternatives such as the summer
pruning method discussed earlier, or fungicides that may be less
harmful to mite predators are being studied.
We are also studying alternatives to chemical fumigation for
apple replant disease. Replant disease, caused by a number of
factors including parasitic nematodes, can occur when a grower
replaces an old orchard with new trees.
Possible alternatives for suppressing parasitic nematode
populations include planting cover crops of canola, marigold, or
new turfgrass varieties before planting new apple trees, or
incorporating peat moss, compost, or water-absorbent co-polymers
into the soil of the planting hole.
Marketing and Economic Issues
Scab-resistance, together with advanced IPM strategies can
provide growers with both production and marketing advantages.
For example, one study indicated that a grower could save
$178 per acre by growing scab-resistant cultivars instead of
McIntosh or Empire. However, since this savings is only 3 percent
of the crop value (assuming 725 bushels/acre @ $8 per bushel),
the productivity and quality of scab-resistant cultivars must be
high to realize a profit. Early yield data and taste panels from
some scab-resistant cultivars show promise in both quantity and
quality. Consumers who have been surveyed say that the newer
releases taste as good, or better, than the current favorites.
In another study, an IPM program using scab-resistant
cultivars had 1/3 the cost and 1/4 the pesticide use of a typical
IPM program using standard varieties. Unfortunately, sooty blotch
and flyspeck, though "minor" problems, can make the crop
unmarketable in current mainstream marketing channels unless
consumer acceptance increases. While growers say it is difficult
to motivate consumers, who are often reluctant to change, some
growers have shown it can be done in niche markets.
While we are a long way from many of the answers we are
seeking, we hope that this project is bringing the day closer
when the Northeast will have sustainable apple production systems
in place. And, we hope that our research on scab-resistant
cultivars will help Northeast growers growers avoid some of the
risks associated with establishing a new variety in their
orchards.
By Dr. Richard A. Casagrande
Professor of Entomology, University of Rhode Island
There should be no need to apply pesticides to trees and shrubs
in the landscape. Carefully selected plants that are properly
sited and maintained will escape the ravages of serious insect
and disease pests and should outlast any of us.
For the most part, however, consumers don't know much about
the pests of trees and shrubs, and growers tend to plant whatever
sells. Thus our landscapes contain many plants that require
extensive management and excessive pesticide applications, but
still die prematurely.
Recently, for example, I came across a Rhode Island bed and
breakfast that was installing a new hedge at considerable
expense. The inn's owners planted approximately 75 Canadian
hemlocks and three flowering dogwoods at an estimated cost of
$6,700, not counting labor.
The property owners can now look forward to annually
applying insecticides against the hemlock woolly adelgid, which
is presently killing their neighbor's hemlocks. They'll also need
up to three annual sprays of fungicides on the dogwoods to
control anthracnose disease. With diligent care, these trees will
mature to a size where they are too large and too costly to
spray. They will die later, rather than sooner, with a
substantial cost for removing and replacing them.
These problems could have been avoided.
The hedge could have been planted with Japanese or western
hemlocks. The dogwoods could have been Cornus kousa or Stellar
series hybrids. For roughly the same planting cost, the inn's
owners could have used plants that will withstand pests. In the
long-run, it would have saved them hundreds of dollars in annual
pesticide costs.
With support from growers and the Northeast Region ACE
program, our team is helping landscapers, homeowners and nursery
producers discover and use plants that require less pesticides,
water, and fertilizer. The goal of our project is to get everyone
working from the same menu - a list of sustainable trees and
shrubs.
The list is the key element in our program. But the project
also involves the development of a logo, a point-of-sale tag, a
manual, and demonstration landscapes - all intended to further
the use of sustainable plants.
The first edition of the list, "Sustainable Trees and
Shrubs for Southern New England," was released in September at
URI's GreenShare Field Day. This publication describes
approximately 200 useful landscape plants which, to our
knowledge, are non-invasive and require less water, pesticides,
and maintenance. It also lists 128 common landscape plants which
are more trouble-prone, and the major problems that eliminated
these plants from the sustainable list.
Development of the list has been a cooperative venture
involving the Rhode Island Nurserymen's Association and faculty
from the University of Rhode Island and the University of
Massachusetts. It has been reviewed by two dozen leading experts
in the region, including nursery producers, landscapers,
arboretum managers, and faculty.
How did we gauge the "sustainability" of various plants?
Primarily through observation and experience. We've found that a
number of the plants on our list contain chemicals that seem to
confer protection against insects and pathogens. For other
plants, physical characteristics, such as hairy or waxy leaves
provide protection.
These plants are on display at a demonstration site, the
"Learning Landscape," surrounding the URI Cooperative Extension
Center. This 1.5-acre landscape demonstrates the latest low-
maintenance techniques and plant materials for homeowners.
The demonstration landscape, designed and managed by the
Cooperative Extension Center, received a large boost from the
Rhode Island Nurserymen's Association, which provided the plant
materials and labor (a donation of approximately of $100,000) for
the project.
Trees and shrubs were selected from the sustainable list,
demonstrating many excellent plants less familiar to the trade.
The landscape was dedicated at the GreenShare Field Day. Now in
its third year, GreenShare annually draws about 2,000 people who
are interested in low maintenance landscapes and gardens.
The "Learning Landscape" represents roughly one-quarter of
the grounds surrounding the URI greenhouses. The remaining land
is a formal garden featuring stone walls built through the Works
Projects Administration in the 1940s. We have completed the
design and construction plans for transforming the garden into a
low maintenance landscape. The plans emphasize plants from the
sustainable list and make extensive use of perennials and
groundcovers.
The renovation of this garden will began this fall and
probably will take four to five years to complete - unless we
find a significant source of funding, which could greatly speed
up the process. When complete, the formal garden and "Learning
Landscape" will provide an unparalleled opportunity for the
entire community, including students, homeowners, landscape
architects, and nursery producers, to learn about the use of
sustainable plants and designs.
The sustainable list is available through the URI
Cooperative Extension Center. We're also planning to distribute
it through the University of Massachusetts and elsewhere. Send a
check for $4 to Cooperative Extension Center, University Rhode
Island, Kingston, RI 02881. The proceeds will be used to maintain
the demonstration landscape.
Swapping Sprays for Spores
By Michael Brownbridge
Assistant Research Professor, University of Vermont
In laboratories and test greenhouses, our research team has
been developing a new arsenal against common greenhouse pests:
insect-killing fungi. Our results to date show that these fungal
pathogens, used as part of integrated pest management strategies,
could significantly reduce insecticide use in greenhouse
production.
The greenhouse has an optimal environment for plant
production that, unfortunately, also favors insect survival and
reproduction. Pest outbreaks can precipitate major losses of
revenue through direct feeding damage, transmission of diseases,
and the costs associated with insect control. As a result, insect
control in the greenhouse and nursery industry is still largely
based on the routine use of agrichemicals.
But greenhouse growers want alternatives. In fact, because
of concerns about insecticide resistance, environmental
contamination, restrictive regulations, cost, and food and worker
safety, many leading greenhouse grower organizations have made
bio-control one of their highest research priorities.
Since 1991, we have been testing native insect-killing fungi
against three major pests of greenhouse-grown ornamental and
vegetable crops: western flower thrips, sweet potato whitefly,
and the green peach aphid. More than 150 fungal isolates have
been screened against these three pests.
The results have demonstrated that some fungi might be used
quite effectively to control insect pests. We have found,
however, that there is great variation in the effectiveness of
the fungi for different target pests.
For example, Beauveria bassiana, Metarhizium anisopliae, and
Verticillium lecanii were the most effective species against
western flower thrips and green peach aphid; B. bassiana,
Paecilomyces farinosus and P. fumosoroseus, were the most
effective
against sweet potato whitefly.
How do these fungi kill insects? First, the insects must
come into direct contact with fungal spores. The spores stick to
the cuticle, or exoskeleton, of the insect, until the spore
germinates. The fungus then penetrates the cuticle to reach the
inside of the insect. There, it must overcome the insect's immune
defense mechanisms to establish itself and grow.
Having infected an individual, the fungus kills its hosts in
one of two ways. The fungus can produce toxins that are lethal
to the insect, or the fungus can literally eat away at the inside
of the insect until the insect dies. Once the insect is dead, the
fungus proliferates throughout the insect cadaver.
Once an individual insect dies of a fungal infection, it can
infect other insects. If conditions are favorable - high
temperature and humidity levels - the fungus will grow back
through the cuticle and sporulate on the surface of the dead
insect. These spores can then infect other, healthy insects that
come into contact with them.
Our research thus far has focused on evaluating a range of
pathogens and formulations for use on an assortment of plants,
with the goal of determining which fungi are active against more
than one insect pest species. We have found several isolates to
be effective, at least under lab conditions, at killing several
insect pests.
Presently, we are conducting additional assays to make the
final isolate selections for greenhouse trials. We are also
evaluating fungal preparations in on-plant and in-soil trials
against western flower thrips and in small-scale trials against
sweet potato white flies infesting poinsettias. In the future we
plan to expand the scope of work to include trials on high-value
vegetable crops, such as peppers, cucumbers and tomatoes. Actual
commercial trials might begin in 1995 or 1996.
Before doing commercial trials, we need to determine the
most most effective formulations, optimal dosage rates and best
application procedures for enhanced on-plant performance. We have
established collaborative links with fungal technology companies,
and we hope to begin work soon using formulated materials to
control western flower thrips and sweet potato whitefly
infestations in our experimental greenhouse.
Other areas that will need attention are the integration of
fungi with other pest control strategies and evaluation of their
effects on other biocontrol agents, such as predators and
parasitoids.
Preliminary data suggest that while certain beneficial
species may be susceptible to lethal fungal infections in the
lab, in actual greenhouse conditions they would not contract the
infection because their behavior protects them from exposure to
the spores.
We think the fungi represent a viable, ecologically
acceptable alternative to chemical pesticides. Results to date
have been encouraging, but we still have a long way to go before
a commercial product becomes available.
Furthermore, it would be naive to expect the fungi to
replace all other pest management options. Rather, their
development as dependable and inexpensive components of IPM will
reduce our reliance on chemical insecticides while providing
long-term benefits to growers and the environment.
Michael Brownbridge is an entomology assistant research
professor at the University of Vermont. UVM Professor Bruce
Parker and Assistant Professor Margaret Skinner are collaborators
in this research. They are concluding their first year of SARE-
and ACE-supported research on the use of fungal pathogens.