Predatory Mites Benefit
Apple Growers
in Pennsylvania
Pennsylvania tree fruit growers could potentially
save up to one million dollars per year in
pesticide applications, reduce their pesticide
usage by almost one ton of active ingredient,
as well as receive federal conservation payments,
thanks to a predatory mite recently discovered
by a Penn State researcher.
Tree fruit is a $69 million a year industry
in Pennsylvania. At one time, the state was
internationally known as a model system for
the biological control of mites from the
black lady beetle, Stethorus punctum, which
was resistant to organophosphate insecticides.
Conservation of Stethorus as a biological
control agent reduced miticide use by 50
percent (an estimated 2.2 million pounds)
over a 15 year period, saving growers an
estimated $20 million. However, the introduction
of new classes of synthetic insecticides
and miticides used to control orchard pests
decimated populations of the black lady beetle
and other predatory mites.
The use of biological controls, such as
predatory mites, is one component of a grower's
integrated pest management (IPM) program.
IPM aims to manage pests—such as insects,
diseases, weeds and animals—by combining
physical, biological and chemical tactics
that are safe, profitable and environmentally
compatible.
According to Dr. David Biddinger, biocontrol
specialist at the Penn State Fruit Research & Extension
in Biglerville, Pa., it was a surprise to
find high numbers of the predatory mite Typhlodromus
pyri (T. pyri) in a commercial apple orchard
in Adams county. "With the implementation
of the Food Quality Protection Act, growers
can no longer use some of the more toxic
compounds in their orchards to control pests
and more selective pesticides are being developed
and applied," explains Dr. Biddinger. "As
a result, we are starting to see new beneficial
insects and mites in the orchard."
Before the introduction of synthetic pesticides
just before World War II, pest mites such
as European red mites and the two-spotted
spider mites were kept under control by predatory
mites such as T. pyri. According to Dr. Biddinger,
it is very important to keep these pests
at bay, because they feed on the leaves of
apple trees, which can reduce fruit quality
and yield. As broad-spectrum insecticides
were introduced to control insect pests,
naturally occurring mite predators were also
killed. This necessitated the use of pesticides
to control the pest mites (miticides). "Miticides
are expensive and mites quickly developed
resistance (immunity) to them, forcing the
pesticide companies to produce new products
and pass related costs onto the grower," he
says.
Armed with the observation that T. pyri
were emerging and a grant from the Pennsylvania
Apple Marketing Board in 2004, Dr. Biddinger
surveyed approximately 20 apple orchards
for the presence of the predator, usually
only detected in orchards in New York and
New England. T. pyri has never been detected
in Pennsylvania or other mid-Atlantic states
before. He found that about three-quarters
of all surveyed orchards contained populations
of the predatory mite. "The survey confirmed
what we already suspected, that T. pyri is
capable of tolerating the hotter summers
of Pennsylvania and can exist in multiple
sites," says Dr. Biddinger.
A 4-year USDA Risk Avoidance and Mitigation
Program (RAMP) grant is allowing Dr. Biddinger
and other researchers to work with seven
apple growers and four peach growers in Adams,
Bedford, and Centre counties using only reduced
risk insecticides to manage pests. Many of
these new insecticides, such as the insect
growth regulators, are not broad-spectrum
in activity, meaning that they target only
specific pests and are not harmful to predatory
mites. "Unlike other predatory mite
species, T. pyri never leaves the tree, even
when pest mite populations decline. They
are able to subsist on pollen and fungal
spores until the pest mites return," Dr.
Biddinger explains. "This close association
with fruit trees allows them to respond to
pest mite populations before the pests can
cause injury, but makes them very susceptible
to pesticides. Just one spray of a toxic
compound can affect predatory mites for the
following three growing seasons."
In addition, a 3-year Pennsylvania Department
of Agriculture grant is allowing Dr. Biddinger
and other researchers at Biglerville to work
specifically with fruit growers throughout
the state to conserve or introduce T. pyri
into apple orchards. "During the first
year of the project, we started the process
of transplanting T. pyri into new orchards.
Researchers either transfer flower clusters
and shoots from a T. pyri orchard in the
spring and summer to a new one, or in the
fall place burlap bands around trunks of
trees to collect overwintering T. pyri and
then transfer the bands to trees in new areas
in the spring," Dr. Biddinger says. "We've
been having great results so far; the predatory
mites seem to adapt well and are building
up quickly in new orchards."
Dr. Biddinger is also working with growers
to conserve T. pyri in sites where it already
exists and advising them as they transition
to beneficial organisms. Since it can take
2 to 3 years for the predator population
to become abundant enough to regulate pest
mites without the need for any miticides,
other measures may be needed to keep the
pest mites under control. "We are advising
growers to use non-toxic oil sprays to augment
mite control and to avoid using toxic insecticides
such as pyrethroids to control other pests.
We visit the orchards bimonthly to help growers
monitor mite populations and give advice," Dr.
Biddinger reports. In addition, the researchers
are presenting information at grower field
days and also providing online updates in
Penn State's Fruit
Times Newsletter.
Not only do growers benefit from reduced
pesticides and production costs, but they
may also receive government payments as an
incentive for adopting these practices. Dr.
Biddinger encourages interested growers to
participate in this incentive program aimed
at supporting this transition to environmentally
friendly pest management and pesticide handling
tactics. The program, Agriculture Management
Assistance (AMA), is administered by the
USDA's Environmental Quality Incentives Program
(EQIP) through National Resources Conservation
Service (NRCS). The program partially reimburses
growers for introduction of various conservation
practices into their farm operations, including
biological controls in an IPM program.
According to Barry Frantz, assistant state
conservationist for programs with the USDA
in Pennsylvania, NRCS, the AMA provides cost-share
assistance to agricultural producers to voluntarily
address issues such as water management,
water quality, and erosion control by incorporating
conservation into their farming operations. "Producers
may construct or improve water management
structures or irrigation structures, plant
trees for windbreaks or to improve water
quality, mitigate risk through production
diversification or resource conservation
practices, adopt integrated pest management
tactics, or transition to organic farming," Frantz
explains.
Applicants may request AMA assistance by submitting an application to the local
NRCS office. Applications (form
CCC-1200), along with additional information about the program. Questions
about the program may be directed to Frantz at (717) 237-2216, or e-mail at barry.frantz@pa.usda.gov.
Currently, Dr. Biddinger says they are testing
new low-toxicity pesticides to see how they
will affect T. pyri and are looking to expand
the program to other areas of the state.
For more information on the project, contact
Dr. David Biddinger at (717) 677-6116 or
by e-mail at djb134@psu.edu.
The Pennsylvania IPM program is a collaboration
between the Pennsylvania State University and the Pennsylvania Department of
Agriculture aimed at promoting integrated pest management in both agricultural
and nonagricultural situations. For more information, contact the program at
(814) 865-2839. Also, you may view archived program news
releases.
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