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United States Department of Agriculture

Agricultural Research Service

Title: Do boll weevils really diapause?

Author
item Showler, Allan

Submitted to: American Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 2009
Publication Date: June 6, 2010
Citation: Showler, A. 2010. Do boll weevils really diapause? American Entomologist. 56(2):100-105.

Interpretive Summary: Boll weevil diapause has been poorly understood since the term was first used 50 yrs ago to describe the pest’s winter dormancy in temperate regions, at least in part because researchers have commonly relied on weak or erroneous assumptions about selected “diapause criteria” that have been widely, and perhaps too quickly, accepted. This literature-based research determined that previous findings regarding the influences of temperature and photoperiod are largely unreliable, confusing, and often contradictory. Hence, diapause as a boll weevil response to winter may have been prematurely claimed while boll weevil dormancy during temperate winters appears to be comprised of a temperature-related slowing of metabolism and locomotion until a threshold is reached for quiescence. Also, the tropical origin of the boll weevil and high overwinter mortality in temperate regions suggests that it did not evolve to endure cold winters and thus may not have developed a true diapause response.

Technical Abstract: Boll weevil, Anthonomus grandis grandis Boheman, diapause has been poorly understood since the term was first used 50 yrs ago to describe the pest’s winter dormancy in temperate regions. This literature-based study found that low temperature and changes in photoperiod are the boll weevil diapause-induction factors most often referred to by scientists. Studies to test the influences of those factors, however, commonly rely on weak or erroneous assumptions about selected criteria that have been widely, and perhaps too quickly, accepted. Although declining temperatures are associated with reduced metabolic and locomotory activity and, under field conditions, with seeking shelter, the capacity of temperature to induce diapause status in boll weevils is contentious largely because of confusing, sometimes contradictory, findings. Experimental results for assessing the influence of photoperiod on diapause induction are also confounded by the same weak diapause characteristics. Other studies have revealed that egg production does not cease under any photoperiod regime, and that active winter populations are able to reproduce in the subtropics. Diapause as an overwintering modality for boll weevils may have been prematurely claimed, resulting in long-held dogma. Rather, boll weevil dormancy during temperate winters appears to be comprised of a temperature-related slowing of metabolism and locomotion until a threshold is reached for quiescence. The tropical origin of the boll weevil and high overwinter mortality in temperate regions suggests that it did not evolve to endure cold winters and thus may not have developed a true diapause response.

Last Modified: 7/25/2014
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