ABW reproductive diapause and key factors affecting its termination

The annual bluegrass weevil (ABW), Listronotus maculicollis, is a destructive pest of golf course turf in the northeastern US and Eastern Canada. The adults overwinter in protected habitats adjacent to playing surfaces from where they migrate in spring to short cut turf areas. Timing of the critical spring insecticide applications is challenging due to the often bimodal and prolonged emergence of overwintered ABW adults. In order to predict the onset of ABW spring oviposition and the optimal time for insecticide applications it is important to know what environmental conditions are conducive for diapause termination. Temperature and photoperiod are the most common factors involved in iniatiation and temination of insect diapause, including many weevil species, especially in temperate climates. Pairs of ABW were individually caged on P. annua plugs, first at five different temperature regimes (7, 12, 17, 21 and 25ºC) and the following year at 21ºC and three photoperiod (10:14, 12:12 and 14:10 L:D - corresponding to winter, spring and summer day lengths, respectively). ABW longevity, oviposition and reproductive status was determined, lower temperature oviposition threshold calculated.