EMERGENCE OF OVERWINTERING BOLL WEEVILS (COLEOPTERA: CURCULIONIDAE) ASSOCIATED WITH MICROMETEOROLOGICAL FACTORS

Authors: Westbrook, John; Spurgeon, Dale; Eyster, Ritchie; Schleider, Paul

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/30/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: The boll weevil is a major cotton insect pest that survives cold winter months in a dormant (non-reproductive) condition, and emerges in the spring to infest cotton fields. The objectives of this study were to determine the effects of meteorological factors on the pattern of boll weevil emergence from winter habitat (leaf litter), and to compare the physical condition of boll weevils that emerged from leaf litter and those captured in traps. Temperature, relative humidity, solar radiation, and precipitation were significantly greater, and barometric pressure was significantly less, on emergence dates than on dates with no emergence. Trapped boll weevils had significantly greater reproductive development than emerged boll weevils. This information on the patterns and mechanisms of emergence from overwintering will help to improve predictive models, risk assessments, and pest management strategies for boll weevils.

Technical Abstract: A field study was conducted in the Brazos Valley of Texas to determine the effects of temperature, humidity, and other meteorological factors on the temporal emergence pattern of boll weevils (Anthonomus grandis Boheman), and to compare the physiological and morphological conditions of emerged and trapped boll weevils. Emergence cages were infested with diapausing boll weevils in the fall. Daily emergence and microclimatic conditions of the leaf litter and air were monitored until the subsequent summer. Temperature, relative humidity, incident solar radiation, and precipitation were significantly greater, and barometric pressure was significantly less, on emergence dates than on dates with no emergence. Emerged and trapped boll weevils were dissected to assess their morphology. Emerged boll weevils tended to exhibit greater fat body development, greater atrophy of testes, and less ovary development than trapped boll weevils. None of the emerged boll weevils were rated extra lean and no trapped boll 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 boll 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 boll weevils.