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Diapause Induction in Subtropical Boll Weevils

D. W. Spurgeon and J. R. Raulston


Diapause induction in adult boll weevils was revisited using a standard feeding regime developed at this laboratory as a baseline for comparison of the effects of photoperiod, nighttime temperature, and feeding regimes more commonly used in such studies. The baseline feeding regime consisted of a single intact square fed each day to each individual weevil. The more traditional feeding regime consisted of feeding 5 debracted squares each day to a group of 25 mixed sex weevils held in a pint carton. Environmental conditions examined included 11 and 13 h photoperiods, in all combinations with thermoperiods of constant 29°C or 29°C daytime and 10°C nighttime. Assessments of fat body, gonad condition, and diapause were obtained from dissections at 6, 9, and 12 d after adult eclosion. Photoperiod did not influence the incidence of diapause by itself or in combination with any other factor. Cool nighttime temperature slowed the development of diapause characters in males but this effect was not demonstrated in females. Feeding regime was the major factor determining the incidence of diapause characters in both sexes. Results indicated that levels of diapause observed are highly dependent on the criteria used to determine diapause, and that seminal vesicle condition in males, an often used criteria, is of questionable value. Our study indicates the need for researchers to adopt a more standard and consistent experimental approach to examining boll weevil diapause, thereby facilitating comparison of results between laboratories and geographical areas.

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pp. 1019 - 1025
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998