Reproductive and survival responses of overwintered boll weevils (Coleoptera: Curculionidae) to diet

Authors: Suh, Charles; Spurgeon, Dale; REARDON, BRENDON - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2019
Publication Date: 1/1/2020
Citation: Suh, C.P., Spurgeon, D.W., Reardon, B.J. 2020. Reproductive and survival responses of overwintered boll weevils (Coleoptera: Curculionidae) to diet. Journal of Entomological Science. 55(1):58-68. https://doi.org/10.18474/0749-8004-55.1.58.
DOI: https://doi.org/10.18474/0749-8004-55.1.58

Interpretive Summary: The boll weevil is a major pest of cotton that overwinters as adults in a non-reproductive dormancy called diapause. Diapause is a response to plant maturity mediated through the diet of the adult weevil. However, flower buds (squares) or young fruit (bolls)on late-season cotton, post-harvest regrowth, or volunteer cotton can also support reproduction, especially in the subtropics and tropics where cotton plants may exist during the fallow season. When cotton plants escape crop destruction efforts they may continue to produce fruit and become heavily infested by overwintered weevils. The potential role of these plants on overwintered weevil survival has not been studied. We obtained newly-captured overwintered weevils from pheromone traps, and examined their responses to starvation, and to square (reproduction-promoting) and boll (diapause-inducing) diets. Few newly-captured weevils had extensive fat reserves or the characters of diapause. Providing these weevils with a square diet rapidly induced reproductive development in both weevil sexes but did not promote fat accumulation. Compared with the square diet, a boll diet promoted more gradual reproductive development in female weevils, but also stimulated in both weevil sexes the development of extensive fat bodies similar to those of diapausing weevils. Although diapause was not re-induced by the boll diet, resulting accumulations of fat allowed substantially greater longevity of boll-fed weevils compared with non-fed weevils. These findings reinforce the importance of eliminating fruiting cotton plants during the fallow season.

Technical Abstract: The boll weevil, Anthonomus grandis grandis Boheman, (Coleoptera: Curculionidae) is a major pest of cotton (Gossypium spp.) that typically overwinters in an adult diapause. Diapause is primarily induced by adult diet, but late-season, post-harvest regrowth, or volunteer cotton also support reproduction, especially in the subtropics and tropics where environmental conditions permit cotton fruiting year around. When cotton plants escape crop destruction efforts they may produce fruit and become heavily infested by overwintered weevils. The ecological implications of these plants on the survival of overwintered weevils have not been studied. We obtained newly-captured overwintered weevils from pheromone traps, and examined the physiological and survival responses of these weevils to starvation, and to square (reproduction-promoting) and boll (diapause-inducing) diets. Few newly-captured weevils exhibited fat body hypertrophy or gonadal characters of diapause. Square feeding rapidly induced a high level of reproductive development in both weevil sexes but little fat accumulation. Compared with the square diet, a boll diet promoted more gradual reproductive development in female weevils, but also stimulated in both weevil sexes the development of hypertrophied fat bodies similar to those associated with diapause. Although diapause was not re-induced by the boll diet, resulting accumulations of fat allowed substantially greater host-free longevity of boll-fed weevils compared with non-fed weevils. Findings of this study identify an additional mechanism by which overwintered boll weevils may utilize fallow-season cotton to enhance survival, and reinforce the importance of eliminating cotton during the fallow season.