Evidence for Obligate Migratory Flight Behavior in Young European Corn Borer (Lepidoptera: Crambidae) Females

Authors: DORHOUT, DAVID - PIONEER HI-BRED INTL.; Sappington, Thomas; RICE, MARLIN - IOWA STATE UNIVERSITY

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2008
Publication Date: 10/1/2008
Citation: Dorhout, D.L., Sappington, T.W., Rice, M.E. 2008. Evidence for Obligate Migratory Flight Behavior in Young European Corn Borer (Lepidoptera: Crambidae) Females. Environmental Entomology. 37(5):1280-1290.

Interpretive Summary: The European corn borer is a major pest of corn in North America and Europe. Understanding movement patterns of adults of this insect is critical to designing more effective strategies to prevent development of resistance to transgenic Bacillus thuringiensis (Bt) corn that is protected against corn borer attack. Previous field studies suggested that European corn borer adults may engage in instinctive migratory flight behavior soon after emergence from the pupal stage. We tested this hypothesis in the laboratory by comparing flight behavior of unmated or mated moths of both sexes at different ages on flight mills. Moths were attached by wire tethers to metal arms in such a way that when the moths flew they could move only in a circle of 1 m circumference. An electric eye counted the revolutions of the flight arms on each of 16 flight mills in an environmental chamber and the data were fed into a computer, making it possible to characterize flight activity of the tethered moths. We found that young females about one day old do indeed engage in continuous long-duration flights that seem to be migratory in nature, and thus serve to take the moths potentially many kilometers from their site of emergence. One-day-old males, in contrast, are less likely to engage in a long-duration flight than females. Likelihood of males making a long-duration flight increased with age, while that of females decreased. Mating the night before flight did not affect flight behavior. Our data are important because they suggest that European corn borers can and do disperse much farther and in larger numbers than previously suspected, and they probably do it before they mate. These results will be used by government and university scientists and modelers in the U.S., Canada, and Europe to improve strategies for delaying development of resistance to Bt corn by incorporating better estimates of dispersal behavior.

Technical Abstract: European corn borer, Ostrinia nubilalis, flight behavior was examined in laboratory experiments. Adults were each tethered to one of 16 round-about flight mills in an environmental chamber, and the data relayed to a computer. Parameters analyzed included duration, distance, and speed of the longest continuous flight, and total time spent in flight during an 8-h night. Comparisons were made between unmated and mated moths of both sexes at different ages between 1 and 5 d post-emergence. For unmated females, both propensity to engage in a continuous long-duration flight, and duration of the longest flight, were highest the first night after emergence, declining significantly by 5 d of age. In contrast, male propensity to make a long continuous flight and its duration were lowest at 1 d of age, increasing significantly by 3 d of age. Flight speed of females was roughly twice that of males at all ages. Mating did not affect flight behavior of either sex at any age tested (2-5 d). The pattern of age-specific flight behavior suggests that unmated females engage in obligate migratory flight the first full night after emergence. The median duration of this flight was about 2 h in our experiments, with some moths flying continuously for the full 8 h of darkness. Females of other ages and males of all ages tested were capable of long-duration flights, but they more likely represent foraging flight. These results help explain the high dispersal rate of newly emerged adults from release sites in field experiments.