Diapause in the Boll Weevil (Coleoptera: Curculionidae) : Seasonal Occurrence in Mississippi Populations

Ann. Entomol. Sm. Am. 92(3): 362-395 (1999) ABSTRACT This study examines the diapause response among boll weevils collected as immatures in squares at different times of the summer and held under simulated field photoperiods and temperatures of northern Mississippi. The percentage of adults exhibiting prediapause increased seasonally, starting with the 1st generation in July and achieving a maximal rate of 96.7% late in the year. A greater proportion of males achieved diapause than females at any given time, except late in the season when convergence in the diapause response of both sexes occurred. These results suggest that individuals in a population have different thresholds of sensitivity to the environmental cues regulating the onset of diapause. Models described the percentage of males and females in prediapause as a function of Julian date of emergence and daylength on the day of emergence. The latter models have potential application over a wide region of the Cotton Belt. Information from this study was used to suggest August starting dates for diapause control applications in the mid-Southrecommendations that subsequently were implemented in eradication programs in Alabama and Mississippi.