Emergence of Overwintered Boll Weevils (Coleoptera: Curculionidae) in Relation to Microclimatic Factors

Abstract

The boll weevil, Anthonomus grandis Boheman, enters a diapause state to survive winters in temperate regions and subsequently emerges from overwintering habitats to infest squaring cotton in the spring. Previous research has found that boll weevil overwintering emergence is closely associated with climatic patterns of temperature and precipitation. The objectives of this study were to determine the effects of temperature, humidity, and other meteorological factors on the temporal pattern of boll weevil emergence, and to compare the physiological and morphological conditions of emerged and trapped weevils. Emergence cages were infested with diapausing weevils in the fall. Daily emergence and microclimatic conditions of the leaf litter and air were monitored until the subsequent summer. Air temperature and relative humidity, incident solar radiation, and precipitation were significantly greater on emergence dates than on dates with no emergence. Emerged and trapped weevils were dissected to assess their morphology. Emerged weevils tended to exhibit greater fat body development, a higher frequency of testicular atrophy, and less ovary development than trapped weevils. None of the emerged weevils were rated extra lean and no trapped weevils were rated fat. These results are consistent with previously-reported effects of climatic factors on weevil emergence in other areas of the Cotton Belt, and add new information about the physiological and morphological characteristics of emerged weevils. This information on the dynamics and mechanisms of overwintering provides insight that should be helpful in formulating improved predictive models, risk assessments, and management strategies for the boll weevil.