Camphor effectively repels the multicolored Asian lady beetle and could be a way to repel the insects as they attempt to overwinter indoors, Agricultural Research Service scientists report in a recently published paper.
The results may help researchers balance the need for protecting this beneficial insect against the public’s concern for the nuisance the beetles create when they congregate in people’s homes and businesses. The research was published in the November 2000 issue of the Annals of the Entomological Society of America.
The multicolored Asian lady beetle, Harmonia axyridis, originally from China, was introduced to the United States in 1916. The beetle has been an effective biological control agent for aphids and scale insects.
Researchers with the Chemicals Affecting Insect Behavior Laboratory in Beltsville, Md., used bioassays to determine the ability of the plant compounds camphor and menthol to repel the beetle. Preliminary test results indicate that camphor and menthol vapors are an irritant to the beetle’s chemosensory organs. These organs--like little taste buds--were found to be so sensitive that the vapors from the two compounds were enough to repel the lady beetles.
Other scientists have found that adult beetles use visual or physical cues to find acceptable overwintering sites. These locations are usually the sunnier or warmer sides of buildings in the afternoon or prominent, exposed, light-colored buildings. Once beetles are at the chosen site, they then resort to using chemical cues to locate the exact crevice they want to inhabit within the structure. Researchers believe that the source of these chemical cues may be beetle feces from the previous winter, the odor of beetles that died at the site, or an attractant pheromone.
This evidence suggests that multicolored Asian lady beetles could be controlled using a “push-pull” strategy. They could be “pushed” from their overwintering sites by the camphor repellant and “pulled” into traps--using chemicals that mimic the natural cues they use to identify sites--without harming them.
By Jesús García, January 30, 2001
ARS is the chief scientific research agency in the U.S. Department of Agriculture.