Entomologists at Montana State University discovered that a particular type of weevil is attracted to a trap of a certain color when outdoors, but shuns it indoors in favor of a trap of another color.

Attempting to develop an effective trap to help control sweet potato weevils, a group of entomologists discovered that the damaging bugs have discerning tastes.

As adults, these weevils (Cylas formicarius) burrow into sweet potato plants and lay their eggs. Their larvae grow inside the plants, and eventually eat their way out, continuing to feed on the leaves, stems and tubers.

The traditonal method of control is with pesticides. But these have proved to be somewhat ineffective against the weevils since the adults might die but the larvae living inside the plant do not. Resistant strains of sweet potato have been developed but are not in widespread use.

As reported by Science News, G.V.P. Reddy, an entomologist at Montana State University, has devoted the past few years to creating a trap that is baited with artificial pheromones that mimic a female weevil.

"Once you remove all the males," Reddy says, "the females can't mate and won't lay eggs. When determining if a color preference existed, Reddy and his colleagues found that, outdoors, red traps attracted nearly twice as many weevils as white and yellow ones. But indoors the weevils ignored the red and other colors while favoring green traps.

The findings are important because the weevils not only attack the sweet potato plant while it is growing, they also feast on the tubers once harvested and stored inside. The findings might also lead to better traps for other pests.