February 22,
2005: A recent article by Joel Grossman in
the IPM Practitioner (Sept/Oct 2004) highlights the
wide range of Integrated Pest Management research being
carried out in nearly every region of the United States,
as reported at the annual meeting of the Entomological
Society of America. While much IPM research is designed
primarily to help conventional farmers reduce their
use of chemical pesticides—especially the most
dangerous compounds—more and more researchers
are investigating principles, materials, and techniques
with practical value for organic farmers.
Some of the most promising work focuses on trap cropping.
Forrest Mitchell of the Texas Agricultural Experiment
Station tested the effectiveness of squash trap crops
for control of squash bugs, Anasa tristis. When planning
trap crops, Mitchell said, farmers should keep in mind
that squash bug feeding preferences among cucurbits
run as follows (from most to least favored): squash
and pumpkins > watermelons > cantaloupes >
cucumbers > wild gourds. In addition, he noted, squash
bugs feed on large plants in preference to small plants,
so trap crops should be planted earlier than primary
crops.
Mitchell emphasized that squash trap crops are highly
effective for watermelons and cantaloupes, where they
can offer better than 90 percent protection from squash
bugs. They are less effective as trap crops for other
squash plants, he said, but still offer good early-season
pest protection and some later-season protection.
Elsewhere in the country, Richard Roush of the University
of California at Davis reported that early potatoes
grown at the margins of tomato, eggplant or later potato
fields can serve as an effective trap crop for Colorado
potato beetle. Once the trap potatoes are infested,
they can be sprayed (by conventional farmers) or flamed
(by organic farmers) to impact the CPB populations.
Alternatively, trenches lined with black plastic can
be constructed along field perimeters—since most
CPB walk into fields early in the season, they get caught
in the trenches and cannot escape.
In a different approach, researchers at Montana State
University reported that farmers on the Northern Plains
could protect crops from wheat stem sawfly (Cephus cinctus),
a relatively new and very damaging pest, simply by setting
their cutter bars higher when they combine. Scott Meers
found that two parasitoids, Bracon cephi and C. lissogaster,
overwinter in wheat stems and are harmed by standard
harvest practices. Farmers can ensure adequate overwintering
habitat for the parasitoids by leaving at least 1/3
of the wheat stem standing when they harvest, Meers
said. Leaving more stem standing, especially within
7.5 to 30 meters of field perimeters, offers the beneficial
species additional protection. Given sufficient habitat,
the parasitoids can virtually eliminate sawfly damage.
Alan Cady of Miami University in Ohio studied the effectiveness
of constructed refugia to encourage predatory ground
beetle and spider populations in corn and soybean fields.
Cady and his team built open baskets (1 meter x .5 m
x .2 m) out of chickenwire, filled them with sterile
wheatstraw, and placed them in and around the fields.
They found that the refugia boosted predatory arthropod
populations in both corn and soybean fields, and in
the corn fields led to reduced insect damage, higher
yields, larger ears, and greater stalk biomass. The
effectiveness of the refugia appeared to be greatest
within about 5 meters of the straw piles.
Finally, a group led by Donald Weber of USDA-ARS Beltsville
has been working to develop textile-based, baited traps
for adult corn rootworms, Diabrotica spp. The adult
leaf beetles are strongly attracted to cucurbitacins,
plant compounds produced by cucurbits. To make the traps,
researchers extracted cucurbitacins from buffalogourd,
Cucurbita foetidissima, and Hawkesbury watermelon,
Citrullus lanatus, and then either sprayed
or soaked a number of different textiles (including
knit polyester, jute burlap, and cotton muslin) with
the compounds. Some of the fabric panels were also treated
with spinosad to kill the attracted beetles. Soaked
burlap was among the most effective trap materials,
Weber reported.
The Entomological Society of America's next annual
meeting will be held Nov. 6-9, 2005, in Fort Lauderdale,
Florida. Abstracts of papers presented at past ESA meetings
can be accessed at www.entsoc.org/annual_meeting.
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