Morphology, diet, and temperature dependent host-free survival of the boll weevil, Anthonomus grandis (Coleoptera: Curculionidae)

Authors: Spurgeon, Dale; Suh, Charles

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2018
Publication Date: 5/29/2018
Citation: Spurgeon, D.W., Suh, C.P. 2018. Morphology, diet, and temperature dependent host-free survival of the boll weevil, Anthonomus grandis (Coleoptera: Curculionidae). Journal of Insect Science. 18(3):8. https://doi.org/10.1093/jisesa/iey047.
DOI: https://doi.org/10.1093/jisesa/iey047

Interpretive Summary: The boll weevil is an important pest of cotton in South America, Mexico, and southernmost Texas in the United States. A key factor in the persistence of the boll weevil is its ability to survive the non-cotton season in an adult dormancy. Mechanisms responsible for this survival in subtropical and tropical areas are incompletely known, and our understanding has been further complicated by unverified reports of overwintering on non-cotton hosts. In addition, the validity of the criteria used to distinguish this dormancy have been questioned. ARS scientists at Maricopa, AZ and College Station, TX showed a relationship between the criteria used to detect dormancy and subsequent survival of weevils isolated from food. This finding demonstrated the criteria to distinguish dormancy have ecological meaning. In addition, survival of starved dormant weevils was enhanced after they had fed on bolls compared with other diets, and was greater when the temperature was around 65 degrees F compared with higher or lower temperatures. The maximum longevity for starved weevils was more than one year at 65 degrees F, which is a temperature typical of the non-cotton season in many tropical and subtropical cotton production regions. These results demonstrate the dormant boll weevil is capable of surviving the non-cotton season in these regions in the absence of presumptive non-cotton hosts.

Technical Abstract: The boll weevil, Anthonomus grandis grandis Boheman, is an important pest of cotton (Gossypium spp.) in South America, Mexico, and southernmost Texas in the United States. A key factor in the persistence of the boll weevil is its ability to survive the non-cotton season. Mechanisms facilitating this survival in subtropical and tropical areas are incompletely known, and our understanding has been further complicated by recent reports of overwintering on non-cotton hosts. In addition, the nature and even existence of the adult dormancy, and validity of the criteria used to distinguish it, have been questioned. We manipulated the boll weevil diet to produce a range of diapause responses and observed the corresponding host-free survival patterns. The estimated proportion of diapause was associated with subsequent survival. In addition, different diets producing similar incidences of diapause resulted in substantially different host-free longevity, and the longest survival was observed for weevils fed bolls as adults. Survival patterns exhibited a negative temperature-dependence except for the lowest observed temperature (12.8 degrees C), where survival was reduced compared with that at 18.3 degrees C. This suggests chronic chilling injury in response to extended exposure to low, above-freezing temperatures. All but the highest temperature (29.4 degrees C) facilitated survival >6 mo., and survival of >1 year was observed at 18.3 degrees C. The temperatures permitting the greatest survival are typical for many subtropical and tropical regions during the non-cotton season, indicating that diapausing boll weevils are capable of surviving the non-cotton season in these regions without the benefit of presumptive non-cotton hosts.