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Efficacy of Early Insecticides and Their Effect on Yield and Maturity of Bt Cotton

J. T. Ruscoe, G. L. Andrews, J. B. Phelps and B. R. Savoy


Little is known about effects of early season insecticides in Bt cotton Gossypium hirsutum L. Field studies were established in a commercial, cotton production system in the Mississippi Delta in 1997 to examine the effects of various insecticide treatments on insect populations. Sampling of plant growth, squaring rates, date of node above white flower 5 (NAWF5), and lint cotton yields was done to determine if early season insect feeding affected these plant variables. Intense sampling allowed for an accurate description of the insect populations in the field during the physiological development of fruiting branches below node 10. This allowed for an examination of insecticide efficacy, and the calculation of insect day data for the period when the first fruiting branches were initiated. Measurements of plant anatomy and maturity stages allowed for the quantification of plant damage done by insect populations by regressing insect days on plant measurements. Differences among insecticide treatments were measured through insect numbers and plant damage. Regression of yellowstriped armyworm, Spodoptera ornithogalli (Guenée), days on terminal damage is shown to be significant and positive. Regression of both yellowstriped armyworm and tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), days produced significant negative regressions. Regression using two independent variables (armyworm days and Lygus days) was shown to be significant and negative when regressed on percent square set of cotton with 10 mainstem nodes.

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pp. 1043 - 1049
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998