Microbes Help Scientists Sucker Sap Beetles

For the first time, scientists have identified chemical signals that pineapple beetles heed to find food. The pests swarm to unusual airborne compounds made by microbes in addition to more common aromas emitted by decaying fruit.

The discovery by Agricultural Research Service scientists gives researchers a broader view for finding ways to synthesize "calling cards" to most effectively trap various species of nitidulids, also known as sap beetles. Someday, traps that monitor nitidulids may be used by growers and shippers to decide whether to apply pesticides.

Nitidulid control may become increasingly important with the advent of "green" methods to control other insects. For example, some sweet corn is genetically engineered with a protein to fight off caterpillars, reducing the need for insecticide applications. Nitidulids are undeterred by the protein. As use of insecticides that normally control both types of insects is discontinued, nitidulids may thrive and inflict widespread kernel damage.

In addition to munching on pineapple, the pineapple beetle—Carpophilushumeralis—feeds on dates, citrus and sugarcane.

In tests at the National Center for Agricultural Utilization Research at Peoria, Ill., three newly isolated microbial compounds attracted the pineapple beetles in a wind tunnel. The compounds were 4-ethyl-2-methoxyphenol, 2,5-diisopropylpyrazine and 2-phenylethanol. The pyrazine had never before been found in nature.

Generally, Robert J. Bartelt, an entomologist with USDA's Agricultural Research Service, and Bruce Zilkowski, a technician turned support scientist, have found that when males of other nitidulid species get a whiff of a favorite fermenting food, they make their own additional chemical attractants called pheromones to call males and females alike to dinner. And it seems, the more complex the mix, the merrier.

The researchers have synthesized pheromones produced by nine other nitidulid species.

An article about the sap beetle research appears in the April issue of Agricultural Research magazine, available online at:

/is/AR/archive/apr99/micr0499.htm

Scientific contact: Robert J. Bartelt, ARS National Center for Agricultural Utilization Research, Peoria, Ill., phone (309)681-6237, bartelrj@mail.ncaur.usda.gov.