Author
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Spurgeon, Dale |
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Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/11/2007 Publication Date: 3/5/2008 Citation: Spurgeon, D.W. 2008. Seasonal patterns in host-free survival of the boll weevil (Coleoptera: Curculionidae) in the subtropics. Journal of Entomological Science. 43(1):13-26. Interpretive Summary: Details of the mechanisms of how the boll weevil survives the non-cotton season in the subtropics are not well known. This information may be critical to improving eradication efforts in the Lower Rio Grande Valley of Texas. In cage studies of the survival of weevils denied food after an initial feeding period, host-free survival of weevils held outdoors followed a seasonal pattern while survival of those held under controlled conditions did not. When survival patterns of weevils held outdoors were adjusted for seasonal differences in temperatures, seasonal differences in survival were reduced but not eliminated. For groups of weevils held during the warmest weather of the season, survival of weevils fed outdoors for 21 days was greater than for weevils fed outdoors for 28 days, and survival of weevils held outdoors was lower than for weevils held under controlled conditions. These observations suggest that the length of the feeding period and prevailing temperatures during the survival period both influence survival. These results suggest the opportunity to reduce overwintering weevil populations in subtropical regions through cultural methods such as delayed planting of cotton. Technical Abstract: The overwintering ecology of the boll weevil, Anthonomus grandis Boheman, in the subtropics is poorly understood. Knowledge of seasonal patterns of host-free survival may be important to eradication efforts in the Lower Rio Grande Valley of Texas. The host-free survival of weevil cohorts emerging between 1 June and 3 November 1994 was examined. Weevils were fed either outdoors for 21 d (nine cohorts), outdoors for 28 d (six cohorts), or under controlled conditions (29.4 +/- 1 degree C, 13:11 [L:D] h photoperiod; five cohorts) for 21 d. Weevils were fed cotton (Gossypium hirsutum L.) squares or bolls, depending on availability in the field, and were subsequently held without food in the same environment in which they were fed. Survival of weevils fed outdoors exhibited a marked seasonal pattern in which greater survival was associated with the later cohorts. However, survival of cohorts fed and held under controlled conditions exhibited no seasonal pattern. When survival was adjusted for degree-day accumulations, using a base temperature of 12.8 degrees C, differences in survival curves of weevils fed outdoors were reduced but not eliminated. During the periods of highest degree-day accumulations, most cohorts fed outdoors for 21 d exhibited greater survival than those fed outdoors for 28 d, and survival tended to be greater for weevils fed under controlled conditions than for weevils fed outdoors. These observations suggest the feeding period duration influenced subsequent survival suggests the opportunity to reduce overwintering weevil populations in subtropical regions through a delayed planting tactic. |
