European corn borer, Ostrinia nubilalis, flight behavior was examined in laboratory experiments. Adults were each tethered to 1 of 16 round-about flight mills in an environmental chamber, and the data were relayed to a computer. Parameters analyzed included duration, distance, and speed of the longest continuous flight and total flight time during an 8-h night. Comparisons were made between unmated and mated adults of both sexes at different ages up to 5 d after emergence. For unmated females, duration of the longest flight was highest the first night after emergence, declining significantly by 5 d of age. In contrast, duration of the longest flight for males was 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, but mated adults could not be tested before 2 d of age because the first night was needed for mating. 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 ≈2 h in our experiments, with some adults 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. KeywordsOstrinia nubilalis, migration, dispersal, flight behavior, flight mill ABSTRACT European corn borer, Ostrinia nubilalis, ßight behavior was examined in laboratory experiments. Adults were each tethered to 1 of 16 round-about ßight mills in an environmental chamber, and the data were relayed to a computer. Parameters analyzed included duration, distance, and speed of the longest continuous ßight and total ßight time during an 8-h night. Comparisons were made between unmated and mated adults of both sexes at different ages up to 5 d after emergence. For unmated females, duration of the longest ßight was highest the Þrst night after emergence, declining signiÞcantly by 5 d of age. In contrast, duration of the longest ßight for males was lowest at 1 d of age, increasing signiÞcantly by 3 d of age. Flight speed of females was roughly twice that of males at all ages. Mating did not affect ßight behavior of either sex at any age tested, but mated adults could not be tested before 2 d of age because the Þrst night was needed for mating. The pattern of age-speciÞc ßight behavior suggests that unmated females engage in obligate migratory ßight the Þrst full night after emergence. The median duration of this ßight was Ϸ2 h in our experiments, with some adults ßying continuously for the full 8 h of darkness. Females of other ages and males of all ages tested were capable of long-duration ßights, but they more likely represent foraging ßight. These results help explain the high dispersal rate of newly emerged adults from release...

The effect of genetically modified corn (event MON810, YieldGard Corn Borer) expressing the Bacillus thuringiensis sp. kurstaki (Berliner) (Bt) endotoxin, Cry1Ab, on the survival of western bean cutworm, Striacosta albicosta (Smith), larvae was examined during intraguild competition studies with either European corn borer, Ostrinia nubilalis (Hübner), or corn earworm, Helicoverpa zea (Boddie), larvae. Competition scenarios were constructed by using either a laboratory or field competition arena containing one of five different diets and one of 13 different larval size-by-species scenarios. The survival of western bean cutworms competing with corn earworms in the laboratory arenas on either a meridic diet or isoline corn silk diet was significantly lower (P < or = 0.01) than the controls in 13 out of 14 competition scenarios and larval survival was frequently zero. In contrast, the survival of western bean cutworm competing with corn earworm on a Cry1Ab-MON810 corn silk diet was significant higher (P < or = 0.01) than the controls in four out of six competition scenarios. The results observed in the three way competitions involving the addition of European corn borers generally did not alter the outcomes observed in the western bean cutworm and corn earworm only two-way competitions. These data suggest that Cry1Ab-MON810 corn may confer a competitive advantage to western bean cutworm larvae during intraguild competition, particularly from corn earworms, and that western bean cutworms become equal competitors only when they are of equal or larger size and the diet is Cry1Ab-MON810 corn.

The microsporidian Nosema pyrausta Paillot is a common and widespread pathogen of European corn borer, Ostrinia nubilalis (Hübner), in North America and Europe. Nosema negatively affects European corn borer longevity and fecundity. In this study, we used flight mills to examine the effects of Nosema infection on flight activity of unmated males and females at 1 and 3 days after pupal eclosion, taking the level of infection, as measured by number of Nosema spores per mg of tissue, into consideration. Nosema infection had a significant negative effect on distance, duration and speed of the longest uninterrupted flight, as well as on total distance and duration of flight of 1-day-old males, but not of 3-day-old males or females of either age. However, when insects with a light infection (<15 spores>/mg) were pooled with uninfected moths, significant negative effects of a moderate/heavy infection (≥15 spores/mg) were observed for most flight parameters in 1-day-old, but not 3-day-old, moths of both sexes. The magnitude of reduction was often substantial: e.g., distance and duration were sevenfold, and 3.5-fold less, respectively, in 1-day-old females with a moderate/heavy infection. Flight distance and duration were significantly negatively correlated with level of Nosema infection in 1-dayold, but not 3-day-old, moths of both sexes. The percentage of moths of either sex or age with a moderate/ heavy Nosema infection flying given distances was less than that of lightly infected (<15 spores>/mg) moths. Among uninfected adults, forewing length was positively correlated with several measures of flight performance in males, but not females. However, some performance measures were correlated with wing length in females when infected with Nosema. Nosema infection was associated with reduced adult weight, but not forewing length, suggesting that negative effects of Nosema infection on flight performance are related to reduced energy reserves rather than smaller body size per se.