The Role of Attractants and Feeding Stimulants in The Selection of Cucurbita Flowers by Diabroticite Beetles, (Coleoptera: Chrysomelidae)

173 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.The floral fragrance of the male blossoms of Cucurbita maxima was analyzed chemically to determine the presence of olfactory stimulants for diabroticite beetles. While the mixture contained at least 40 components only one, indole, produced a substantial response in an electroantennogram bioassay. Field testing of indole using sticky traps showed it to be a potent attractant of the western corn rootworm, Diabrotica virgifera virgifera Le Conte and the striped cucumber beetle, Acalymma vittatum (Fabr.). The southern corn rootworm, Diabrotica undecimpunctata howardi Barber, however, was not attracted to indole baited traps. Western corn rootworm trap catch was found to vary seasonally with a period of low trap catches corresponding to the tasseling and silking period of the corn. Field measurements suggest that female western corn rootworms are more responsive to indole than males. However, this difference may be only a reflection of field sex ratios which vary seasonally.An attempt was also made to correlate distributional patterns of diabroticite beetles in Cucurbita blossoms with several flower characteristics involved in feeding or orientation. The content of cucurbitacins, known diabroticite feeding stimulants, and the release of indole correlated positively with diabroticite preference. Analysis by stepwise multiple regression showed cucurbitacin content to be the most reliable predictor of preference, although interactive effects involving indole release may also be of importance.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD