Termination of diapause in the boll weevil (Coleoptera: Curculionidae)

Authors: Spurgeon, Dale; Suh, Charles

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2018
Publication Date: 3/25/2019
Publication URL: http://handle.nal.usda.gov/10113/6471135
Citation: Spurgeon, D.W., Suh, C.P. 2019. Termination of diapause in the boll weevil (Coleoptera: Curculionidae). Journal of Economic Entomology. 112(2):633-643. https://doi.org/10.1093/jee/toy392.
DOI: https://doi.org/10.1093/jee/toy392

Interpretive Summary: The boll weevil is a major pest of cotton in Mexico, South America, and South Texas in the United States. The ability of the boll weevil to survive extended cotton-free periods in a dormant state has been key to its persistence as a pest. However, the mechanism facilitating this survival is poorly known. Adult diapause, in which a long-duration dormancy is induced in advance of the non-cotton season, has long been considered the principal survival mechanism. However, some have characterized the dormancy as a quiescence that is induced, and terminated by the resumption of reproduction, in response to immediate conditions. When dormant adult weevils were provided a diet favoring reproduction a small number of female weevils terminated the dormancy but males did not. Even when the weevils were starved 21 days or more before they were provided a reproductive diet, most weevils remained dormant. When the weevils were forced to fly before they were provided a reproductive diet, more than 50% of the weevils terminated the dormancy. Both feeding and egg-laying activity changed when the dormancy was terminated. These results indicate the dormancy exhibited by the weevil is a diapause rather than a quiescence. A conceptual model recognizing population variation in the induction and termination of diapause is consistent with reports of host-free survival, and accommodate perceived differences in boll weevil ecology among temperate, subtropical, and tropical regions. This model provides a framework which will be valuable to research, management, and eradication efforts in the tropics and subtropics.

Technical Abstract: The boll weevil, Anthonomus grandis grandis Boheman, is a major pest of cotton (Gossypium spp.) in Mexico, South America, and South Texas in the United States. The ability of the boll weevil to survive extended cotton-free periods has been key to its persistence as a pest despite intensive control efforts. However, the mechanism facilitating survival has been subject to debate. Whereas adult diapause has long been considered the principal survival mechanism, some authors have characterized the dormancy as a quiescence. We induced dormancy in the weevil and examined whether food type, enforced starvation, or induced flight influenced termination of the dormancy. Providing dormant adult weevils a diet favoring reproduction for 7-14 days prompted a modest termination response in female weevils and virtually no response in males. Some weevils starved 21 days or more resumed reproduction after exposure to a favorable diet, but most weevils remained dormant. Induced flight followed by exposure to a favorable diet prompted >50% of the weevils to terminate the dormancy. Patterns of feeding and oviposition were also useful in interpreting the termination response. These results indicate the dormancy exhibited by the weevil is a diapause of variable intensity rather than a quiescence. A conceptual model recognizing population heterogeneity in diapause induction and intensity is consistent with reports of host-free survival, and accommodate perceived differences in boll weevil ecology among temperate, subtropical, and tropical regions. This model provides a framework which will be valuable to research, management, and eradication efforts in the tropics and subtropics.