MANAGING THE DISPERSAL OF LADYBIRD BEETLES (COL., COCCINELLIDAE) - USE OF ARTIFICIAL HONEYDEW TO MANIPULATE SPATIAL DISTRIBUTIONS

We tested whether large-scale distributions of aphidophagous ladybirds could be manipulated by localized application of artificial honeydew. In addition to enhancing local build-up of ladybird numbers (e.g., in areas of incipient aphid outbreak), such an approach may prove useful for drawing ladybirds out of a crop scheduled for insecticide treatme nt. In six experiments, we sprayed sucrose dissolved in water to small plots in the center of large alfalfa fields in Utah. Within 48 hours, ladybird densities in the plots increased 2-13x, whereas ladybird den sities al distances of 40-150 m from the plots decreased to a mean of less than two-thirds their former density. We then applied sucrose in a narrow band along the entire perimeter of an alfalfa field; densitie s of ladybirds increased following treatment both along the treated fi eld edge and in untreated alfalfa throughout the field. Finally, we co mpared the numerical responses of two ladybird species to sucrose appl ication; both species responded positively, but Coccinella transversog uttata did so consistently more strongly than did C. septempunctata. O ur results suggest that both promise and challenges lie in the use of artificial honeydew to direct the dispersal and spatial patterns of la dybirds.