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Title: Relationships of Abscised Cotton Fruit to Boll Weevil (Coleoptera: Curculionidae) Feeding, Oviposition, and Development

item Showler, Allan

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2007
Publication Date: 2/4/2008
Citation: Showler, A.T. 2008. Relationships of abscised cotton fruit to boll weevil (Coleoptera: Curculionidae) feeding, oviposition, and development. Journal of Economic Entomology. 101(1):68-73.

Interpretive Summary: Cotton squares and bolls commonly abscise during the growing season but relationships of those fallen fruit to their utilization by boll weevils has not been described. This study, on fallen cotton fruit, reports the results of one of a series of studies that relates planting date to cotton fruit damage by boll weevils. Abscission of cotton fruiting bodies occurs for different reasons depending on the stage of growth and planting date, boll weevils affect certain stages of growth more than others, and, as such, some stages of cotton fruit, particularly large (5.5-8-mm-diameter) contribute more to boll weevil population growth than other stages (such as smaller squares and bolls).

Technical Abstract: Abscised cotton, Gossypium hirsutum L., fruit in field plots planted at different times were examined to assess adult boll weevil, Anthonomus grandis grandis Boheman, use of squares and bolls during 2002 and 2003 in the Lower Rio Grande Valley of Texas. Although boll abscission is not necessarily related to infestation, generally more bolls abscised than squares and abundances of fallen bolls were not related to the planting date treatments. During one year, fallen squares were most abundant in the late-planted treatment. Although large squares (5.5–8-mm-diameter) are preferred for oviposition, diameter of squares is not a reliable measurement after abscission because of shrinkage under field conditions. Fallen feeding-punctured squares and bolls were most abundant in late plantings but differences between fallen feeding-punctured squares versus fallen feeding-punctured bolls were found in only one treatment in 2003. During the same year, fallen oviposition-punctured squares were more numerous in the late-planted treatment than in the two earlier treatments. Treatment effects were not found on numbers of oviposition-punctured bolls, but fallen oviposition-punctured squares were more common than bolls in the late-planted treatment as compared to one of the two earlier treatments each year. Dead weevil eggs, larvae, and pupae inside the fallen fruit were few and treatment effects were not detected. Living third instars and pupae were more abundant in fallen squares of the late-planted treatment than in the earlier treatments and bolls of all three treatments. This study shows that fallen squares in late-planted cotton contribute more to adult boll weevil populations than bolls, or squares of earlier plantings.