Pesticide and Environmental Update
Eggplant's
Flea Beetle "Calling Card" is Read
A rude surprise could be in store for the eggplant flea beetle, bane of
commercial growers and home gardeners alike. Agricultural Research Service
(ARS) scientists have identified a blend of compounds produced by the
pesky leaf eater that could usher in baited traps to lure it to its doom.
The beetle, Epitrix fuscula, is most destructive in the spring, when
eggplant seedlings are transplanted from the greenhouse to the field and
are less tolerant of defoliation. It also attacks other solanaceous crops,
like tomato. Insecticide spraying and cultural practices are the chief
means of controlling the pest, which occurs throughout the United States
but is most common in the South.
Traps or monitoring stations baited with synthetic versions of its
aggregation pheromone—a kind of chemical call to gather for mating and
feeding—could help growers better time their spraying, or even reduce
their insecticide use, notes ARS entomologist Bruce Zilkowksi. Along with
colleagues Bob Bartelt, Allard Cossé and Richard Petroski—all with the
ARS National Center for Agricultural Utilization Research (NCAUR) in
Peoria, Ill.—Zilkowski will describe the research in an upcoming issue
of the Journal of Chemical Ecology.
In host-feeding studies at the center's Crops Bioprotection Research
Unit, Zilkowski and research colleagues identified six volatile compounds
that male E. fuscula beetles emit while feeding on eggplant leaves. They
synthesized the compounds and monitored both male and female beetles'
sensory responses using a technique called electro-antennographic
detection. The most abundant compounds—(2E,4E,6Z)-2,4,6-nonatrienal and
(2E,4E,6E)-2,4,6-nonatrienal—stimulated the greatest electrical response
in the test insects' antennae.
In field studies with eggplant at the NCAUR and at an organic farm in
spring 2005, traps containing synthetic forms of the two attractive
compounds captured 500 percent more male and female beetles than unbaited
controls. Zilkowski's team is now trying to fine-tune the ratio of the
compounds for maximum performance. They're also examining the compounds'
tendency to form isomers, and attempting to determine whether these
structurally different variants will help or hinder the development of a
commercial pheromone formulation.
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