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Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/8/2004 Publication Date: 8/1/2004 Citation: Showler, A.T. 2004. Influence of cotton fruit stages as food sources on boll weevil (Coleoptera: Curculionidae) fecundity and oviposition. Journal of Economic Entomology. 97(4):1330-1334. Interpretive Summary: Insecticide applications for control of boll weevils at the early fruiting stage of cotton, when buds (cotton squares) are small, has not previously shown conclusive advantages for protecting the crop in southern Texas. This research shows that more boll weevils develop eggs, and more eggs are developed in each female, when fed on large buds rather than on small buds or on mature fruit (cotton bolls) of any age. Because boll weevils also prefer to feed on and lay eggs in large buds in the field, protection of the large buds instead of small buds might be a more effective management strategy. Technical Abstract: Boll weevil, Antononmus grandis grandis Boheman (Coleoptera: Curculionidae), populations in the Lower Rio Grande Valley of Texas increase strongly during the squaring stage, and pre-emptive insecticide sprays at the pinhead square stage were designed to capitalize on that association. Laboratory assays showed that cotton plant volatiles, or leaves as a food source, do not elicit egg production in wild weevils. Boll weevils fed on large (5.5-8 mm diameter) squares for 7 d resulted in >/= 3.8-fold more gravid females that developed 4.8-fold more chorionated eggs per female than weevils fed on match-head-sized squares, or post-bloom, young (5-10 d old), or old (3-5 wk old) bolls. When presented with a choice, non-gravid females preferred to feed on young and old bolls 4.7 and 8.4 fold more, respectively, than on large squares. In the field, large squares had 7.8 and 25 fold more feeding punctures than match-head-sized squares and bolls, respectively. Oviposition increased >/= 2.7 fold when females fed on large squares compared with match-head-sized squares and bolls. Preference for large squares as food during squaring, and the associated greater fecundity explain rapid weevil population build-ups shortly after large squares become well established. Based upon these findings, an alternative boll weevil insecticide application strategy is suggested in place of automatic, early-season pinhead square applications, and some later applications that are based on an oviposition damage threshold. |
