SEASONAL EMERGENCE-TIME EFFECTS ON ADULT LONGEVITY, FECUNDITY, AND EGG VIABILITY OF NORTHERN AND WESTERN CORN ROOTWORMS (COLEOPTERA, CHRYSOMELIDAE)

Seasonal emergence time was studied to determine its influence on adul t vigor and reproductive fitness of field-collected Diabrotica barberi Smith & Lawrence and D. virgifera virgifera LeConte. Time of emergenc e was divided into six 2-wk intervals (lots; pooled from beetles colle cted every 2 d from onset to end of seasonal emergence cycle), which s erved as treatments. Beetles were maintained in single-insect oviposit ion chambers on a natural diet and were provided soil as an ovipositio n substrate. The experiment was arranged in a randomized complete bloc k design with 10 replicates. Female D. barberi survived, on natural di et for averages of up to 89 d within lots. Earliest emerging (lot 1) b eetles of both species lived significantly longer than those from late r lots, thus suggesting reduced fitness as the season advanced. Lot fe cundity means ranged from 133 to 312 eggs (maximum 1,036) and 357 to 7 36 (maximum 1,864) eggs per female for D. barberi and D. virgifera, re spectively. Corresponding with greater longevity, increased fecundity was also observed with early-emerging females of both species. Beetles emerging during the first part of the growing season appeared to be g enerally healthier and more reproductively fit than their latter-emerg ing counterparts. These Endings may warrant further evaluations to det ermine possible effects on late-season management efforts in adult cor n rootworm suppression programs. Methodologies associated with insect maintenance and assessment of reproductive biology proved suitable for both species, Additionally, these Endings may offer valuable insight needed to refine procedures for laboratory rearing and egg production from D. barberi.