Diapause response of the boll weevil (Coleoptera: Curculionidae) to selected diets

Authors: Spurgeon, Dale; Suh, Charles; Esquivel, Jesus

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2018
Publication Date: 2/6/2019
Citation: Spurgeon, D.W., Suh, C.P., Esquivel, J.F. 2019. Diapause response of the boll weevil (Coleoptera: Curculionidae) to selected diets. Journal of Entomological Science. 54(1):61-78. https://doi.org/10.18474/JES18-49.
DOI: https://doi.org/10.18474/JES18-49

Interpretive Summary: The boll weevil was once the dominant pest of cotton in the United States. Although eradication efforts have dramatically reduced the range of this pest in the U.S., intractable populations remain in southern Texas and northern Mexico that are a threat to adjoining production regions. A key to eliminating these weevil populations may lie in better understanding of the adult dormancy that permits survival through the non-cotton season. ARS scientists at Maricopa, AZ and College Station, TX demonstrated the adult dormancy became increasingly prevalent when the food source reflected increased cotton plant maturity. Whereas daylength was previously thought to control the dormancy, these results relate incidence of the dormancy to crop maturity, which is consistent with accounts of boll weevil population dynamics under field conditions. These findings provide new insights into the dormancy and resulting overwintering ability of weevils in the subtropics, and provide information key to development of new eradication strategies in those production regions.

Technical Abstract: The boll weevil, Anthonomus grandis grandis Boheman, once the dominant pest of cotton (Gossypium spp.) in the United States, is now the most serious cotton pest in South American production regions. Despite eradication efforts in the U.S., intractable populations remain in southern Texas and northern Mexico, and these strongholds represent a threat to adjoining regions. A key to eliminating this pest from the subtropical U.S. may lie in better understanding mechanisms facilitating survival through the non-cotton season. We examined the diapause response to feeding regimes that evaluated the influences of square size, boll size, and food replacement intervals, under photoperiod (13:11, L:D h) and temperature conditions (constant 29.4 degrees C) considered to inhibit diapause. Female weevils exhibited diapause characters earlier than did males on all diets, and physiological status was not reliably evaluated until adults were 9 d of age. When squares fed to groups of weevils were replaced thrice weekly, most weevils responded with symptoms of starvation instead of diapause. In other feeding regimes, incidence of diapause increased with increasingly developed of food items, which may reflect the weevil perception of host maturity. These results are consistent with accounts of seasonality of diapause and host utilization in the subtropics and tropics, as well as accounts of late-season weevil ecology in temperate regions prior to the widespread adoption of mechanized harvest and determinant cotton cultivars. These findings, combined with earlier demonstrations of extended host-free longevity and lack of a photoperiod response, identify food characteristics as a major determinant of boll weevil reproductive diapause.