EFFECT OF FOOD TYPE AND FEEDING RATE ON BOLL WEEVIL DIAPAUSE

Authors: Spurgeon, Dale; Esquivel, Jesus

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/8/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Results of previous studies of boll weevil diapause, the physiological state that allows adults to survive the non-cotton season, have been inconsistent. Identification and understanding of the sources of these inconsistencies would aid in further studies of diapauase. We examined the impacts of selected food types on diapause in an effort to identify potential sources of variation. Because cotton squares (flower bud) collected from the field often appear different from squares grown in the greenhouse, we examined the impacts of square source (field versus greenhouse). We also examined the influence of the size of squares fed to adult weevils. Finally, we evaluated diets of squares, bolls (cotton fruit), and a mixture of squares and bolls for their ability to consistently produce diapausing boll weevils. Square source (field versus greenhouse) did not appear to affect the occurrence of diapause. However, squares from the field tended to be smaller than those from the greenhouse, and the evaluation of square size indicated that small squares reduced the occurrence of diapause compared to large squares. Differences among diets of squares, bolls, or squares plus bolls were subtle, but diets containing bolls tended to cause higher and more consistent levels of diapause than did diets of squares alone. These results suggest that future diapause studies would be more meaningful if food type was controlled more strictly than in previous studies.

Technical Abstract: Reported results of boll weevil diapause studies have been highly variable, often even within studies. Improved understanding of the source of this variation would aid efforts to study diapause in the boll weevil. Impacts of selected food characters and feeding regimes on the diapause response were examined in preliminary studies as possible sources of this variation. .Influence of square source (field versus greenhouse) was examined for both weevils fed singly (1 square/weevil daily) and in groups (1 square/5 weevils daily). Field-collected squares tended to be smaller, paler in color, and with more reddish coloration on the bracts than greenhouse grown squares. Influence of square size was examined by feeding groups of weevils squares with diameters of either <7 mm or >7 mm. Finally, diets of 1 square/5 weevils, 1 boll/10 weevils, or 2 squares plus 1 boll/20 weevils, each fed 3 times weekly, were examined to identify practical feeding regimes consistently eliciting a high level of diapause. Occurrence of diapause in weevils fed field-collected squares was similar to that in weevils fed greenhouse grown squares. However, differences in square size may have masked the effects of square source bacause a diet of squares >7 mm resulted in a higher proportion of diapause than did a diet of squares <7 mm. There was no statistical difference in diapause response among diets of squares, bolls, or both. However, diets incorporating bolls tended to provide a numerically greater and more consistent diapause response than did diets of squares alone. These preliminary results suggest the need for stricter control of diets used in boll weevil diapause studies.