Temperature influences on diapause induction and survival in the boll weevil (Coleoptera: Curculionidae)

Authors: Spurgeon, Dale; Suh, Charles

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2017
Publication Date: 12/23/2017
Citation: Spurgeon, D.W., Suh, C.P. 2017. Temperature influences on diapause induction and survival in the boll weevil (Coleoptera: Curculionidae). Journal of Insect Science. 17(6):124.

Interpretive Summary: The boll weevil has been the most important pest of cotton wherever it occurs. Although eradication programs in the U.S. have reduced the range of this pest, the weevil remains an intractable problem in subtropical Texas, Mexico, and much of South America. A key to managing the weevil in the subtropics and tropics might lie in better understanding its dormant, overwintering phase (diapause) and subsequent survival in regions characterized by relatively high late-season temperatures. ARS scientists at Maricopa, AZ and College Station, TX showed that diapause develops more slowly in adult weevils held under low temperatures compared with weevils held under higher temperatures. However, weevils induced into diapause under low temperatures exhibited enhanced survival in the absence of food, compared with weevils induced under higher temperatures. These findings suggest that potential host-free survival facilitated by diapause occurring in subtropical or tropical production regions may be reduced compared with the dormancy developing in southern temperate regions. This reduced survival potential emphasizes the importance of a maximized host-free season, and suggests that late-season insecticide spray intervals should be short enough to ensure that the number of diapausing weevils developing in late-season cotton is minimized.

Technical Abstract: The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), has been the most important pest of cotton (Gossypium spp.) wherever it occurs. Although eradication programs in the U.S. have reduced the range of this pest, the weevil remains an intractable problem in subtropical Texas, Mexico, and much of South America. A key to managing the weevil in the subtropics and tropics might lie in better understanding its diapause and overwintering survival in regions characterized by relatively high late-season temperatures. We examined the temporal patterns of acquisition of diapause characters at 18.3, 23.9, and 29.4 degrees C, and the effects of temperature during the diapause-induction period on subsequent host-free survival at 23.9 degrees C. Occurrence of diapause characters generally increased with weevil age at all temperatures, but appeared more rapidly with increasing temperature. Acquisition of the diapause characters tended to occur slightly earlier in female weevils compared with male weevils. Despite the slower development of diapause characters at lower temperatures, when adult weevils were fed under low temperatures subsequent host-free survival was enhanced. These results are consistent with reports of increased weevil survival with delayed entry into overwintering. Our findings also suggest that potential host-free survival facilitated by diapause occurring in subtropical or tropical production regions may be reduced compared with dormancy developing in southern temperate regions. This reduced survival potential emphasizes the importance of a maximized host-free season, and suggests that late-season diapause spray intervals should be short enough to ensure that the number of dormant weevils developing in late-season cotton is minimized.