Overwintering Biology of Dalbulus Leafhoppers (Homoptera: Cicadellidae): Adult Populations and Drought Hardiness

Despite the economic importance of the corn leafhopper, Dalbulus maidis (DeLong & Wolcott), little is known about how this maize pest and its congeners survive the dry winter in Mexico. In the field, Dalbulus populations were monitored weekly with yellow sticky card traps for 18 mo at three sites in Jalisco, Mexico. The sites included a maize field, Zea maysL. ; a natural stand of a perennial teosinte, Zea diploperennis Iltis, Doebley & Guzman; and a natural population of gamagrasses, Tripsacum spp., which are maize relatives. At all sites, highest catches of Dalbulus adults occurred during the dry season between October and March. In a laboratory study to test the survival of adult Dalbulus leafhoppers without their host plants, significant differences were detected among leafhopper species. When denied all food and water (absolute drought), Dalbulus species that specialize on maize were more tolerant than those that specialize on gamagrass. Adults reared under environmental conditions that simulate the beginning of the wet season (June-reared) were less tolerant of absolute drought than adults reared under early dry-season conditions (October-reared). When provided water but no food, October-reared D. maidis lived significantly longer than June-reared D. maidis . Survival of females under water-only conditions was significantly longer than that of males. Field observations revealed that gamagrass-specializing D. gelbus DeLong and D. quinquenotatus DeLong & Nault overwinter as continuously developing populations on their hosts. In contrast, our data indicate that D. maidis overwinter as active adults that can subsist, at least in part, on free water in the absence of host plants until the summer rainy season begins. Surviving adults then migrate locally to newly planted maize fields.