The effect of timing and duration of flooding on the survival and hatch pattern of western corn rootworm eggs

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is arguably the most serious insect pest of corn, Zea maysL., in the U.S. Corn Belt. This species overwinters in the egg stage which goes through a period of diapause followed by a post-diapause embryonic development period that leads to egg hatch. Little is known about the interaction between eggs and flooding, therefore a study was conducted to determine the effects of flooding on WCR egg hatch pattern and survival. Each treatment consisted of a petri dish containing 100 WCR eggs placed on sterilized soil. All eggs were approximately the same age and beginning post-diapause development. Treatments arranged in an RCBD with four replications included: 1) eggs on moist soil (control), 2) eggs submerged in water for the first half of the post-diapause development period then water drained off for the remainder of development, 3) eggs submerged during the second half of the post-diapause development period, 4) eggs submerged under water for the duration of the post-diapause development period. Treatments 2-4 had greater survival than treatment 1. Hatch pattern varied among treatments; in general treatment 2 initiated hatch earlier and hatch duration was shorter than the other treatments while treatment 3 had the longest hatch duration. Treatments 1 and 4 had similar hatch patterns. Data suggest that flooding does not kill WCR eggs, but the timing of flooding can significantly affect hatch pattern. Results will be discussed within the context of rootworm development and management.