The Arkansas Program for Insecticide Termination and Defoliation Management

F.M. Bourland, N.P. Tugwell, M.J. Cochran, D.M. Oosterhuis, and J.P. Zhang


Precise timing of insecticide termination and defoliation management is critical to profitable cotton production. Timing of these end-of-season decisions is often based upon subjective criteria with biases toward delayed action to avoid possible yield loss. Our objectives have been to develop plant-interactive criteria that provide precise, objective bases for making these decisions and to integrate them into an expert computer system. The focal plant criterion used in these decisions has been the number of nodes above the uppermost white flower (NAWF). In well-developed plants, NAWF should be 8-10 at first flower, then decline as fruit load increases. Flowering date of the last effective boll population is signalled by NAWF=5. Based on relative NAWF values, growth pattern within a field can be labelled as either Type 1 (NAWF=5 is attained prior to pre-determined critical cutout date) or Type 2 (NAWF=5 is not attained by critical cutout date). Timing of end-of-season decisions in a field having Type 1 growth pattern is based upon the maturation of the last effective boll population. Our data indicate that economic returns are highest when insecticides are terminated at about 350 heat units (60 F base) after NAWF=5 and plants are defoliated at about 850 heat units after NAWF=5. Timing of defoliation in fields having a Type 2 growth pattern depends upon critical time for harvest completion and historical weather data. COTMAN is a computer program that integrates plant data, temperature, and field/farm parameters inputs with historical weather. The program determines the growth pattern for each field, projects alternative risk-related dates for terminating insecticides and applying defoliants, and sequences fields by their relative maturity. Thus, the producer is given information with which critical end-of-season decisions can be made objectively.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 203
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998