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Sorting Out Wheat Stem Sawfly Attractants

Hiding as if in a “Trojan horse,” wheat stem sawfly larvae chewing inside wheat stems sometimes pose problems for farmers in the Northern Great Plains. When technology is developed to predict the danger, farmers will find it easier to decide whether pest control treatments may be warranted.

As a first step, Agricultural Research Service scientists at the National Center for Agricultural Utilization Research, Peoria, Ill., have discovered and synthesized some of the natural odors that attract adult sawflies of one gender to another. Whether or not such odors may one day be used in trap baits to monitor sawfly populations, the discoveries may lead to more novel approaches to limiting sawfly damage.

The scientists focus their research on adult sawflies because once the sawfly eggs are laid and the larvae are feeding safely within wheat stems, insecticide spraying has little effect.

One of the sawfly’s own antennae, suspended between tiny electrodes, provides a main platform for the research that makes use of a technique called coupled gas chromatographic-electroantennographic detection (GC-EAD). In response to odors, the antenna sends out electrical signals to help the scientists pinpoint exactly the few chemicals that are critically important to the sawfly’s behavior. The information helps researchers identify and formulate various mixes of volatile chemicals to research the insect’s behavior in a laboratory wind-tunnel or in the field.

In other research, the Peoria scientists are using GC-EAD to discover attractants for sap beetles that are pests of figs, dates, and corn; other sap beetles that spread a fungus that infects trees, causing oak wilt; exotic leaf beetles that may someday control weedy tamarisk trees along western U.S. streams; exotic flea beetles that now are being used as biological control agents against leafy spurge; and flea beetles that are pests of canola and other crucifer crops.

An article about the research appears in the July issue of ARS' Agricultural Research magazine.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.