Overwintering of Helicoverpa armigera in Austria

Abstract: There is no information about the overwintering survival of the important agricultural pest insect Helicoverpa armigera in Austria, therefore experiments were conducted. Testing the effect of constant negative temperatures in laboratory on diapausing pupae of the cotton bollworm revealed that pupae survive temperatures of -10 °C for about 12 days maximally and they endure an exposure to 0 °C for about 180 days at most. Moreover experiments, in which Helicoverpa pupae were exposed to outdoor winter conditions, demonstrated, that Helicoverpa armigera is able to survive temperatures of the last two winter seasons in Austria. In the winter 2013/2014 in Ramingstein, Zwettl and Mönichkirchen mortality rates never reached the 30% mark, whereas nearly 100% of the pupae overwintered successfully in Vienna. In the last winter season mortality rate in Zwettl and Mönichkirchen was again very low, in contrast to the location at the Rax Mountain, where 100% of overwintering pupae died. Furthermore testing cold adaptation of overwintering pupae showed that pupae are less sensitive to cold at the beginning of exposure to outdoor low temperatures than at the end of winter season. Sublethal effects or terminating diapause could be the reasons for this increasing mortality rate.