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Title: EFFECTS OF PLANTING DATES ON BOLL WEEVILS (COLEOPTERA: CURCULIONIDAE) AND COTTON FRUIT IN THE SUBTROPICS

Author
item Showler, Allan
item Greenberg, Shoil
item SCOTT, ANDY - RIO FARMS, INC.
item ROBINSON, JOHN R. - TEXAS A&M UNIV

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2005
Publication Date: 6/1/2005
Citation: Showler, A., Greenberg, S.M., Scott, A.W., Robinson, J.R. 2005. Effects of planting dates on boll weevils (Coleoptera: Curculionidae) and cotton fruit in the subtropics. Journal of Economic Entomology. 98(3):796-804.

Interpretive Summary: The date of cotton planting can impact boll weevil populations and damage to the cotton crop, but this has not been studied in the subtropical conditions of the Lower Rio Grande Valley of Texas. Early planting reduced production of squares (fruit), but boll weevil populations were also lower when squares were being produced; late planting was associated with greater production of squares, but this was off-set by greater boll weevil infestations. Delayed planting can profit growers by saving between $18 and $153 per acre in contrast to planting late, but the delayed approach was not consistently superior to early planting in terms of economic returns.

Technical Abstract: The effects of planting dates 2-3-wk apart on boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), populations, and feeding and oviposition damage to cotton, Gossypium hirsutum L., squares and bolls, were studied during 2002 and 2003 in the Lower Rio Grande Valley of Texas. Squares were 44-56% more abundant in some late-planted treatments than in the early-planted treatments, but mean cumulative numbers of oviposition- and feeding-damaged squares were 2.7-4.8-fold more numerous in some late treatments than in the early treatments. Increased square production in later-planted cotton was off-set by greater boll weevil infestations that occurred around cut-out. Early planting avoided boll weevil population build-ups when large squares, which accelerate weevil reproduction, were most abundant. Lint yields in 2002 did not differ significantly between the planting date treatments, but in 2003 mean yield in the middle treatment was 23% greater than in the early and late treatments. Insecticide sprays in the early treatment, based on the 10% damaged squares threshold, were >33% and >43% fewer than in the middle and late treatments, respectively. Delayed planting, especially relative to the onset of favorable cotton-growing weather, is more cost-effective than planting too early or too late.