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
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.