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Integrated Johnsongrass Management in Cotton with Reduced Rates of Clethodim and Cultivation
Enrique Rosales-Robles, James M. Chandler, Scott A. Senseman, and Eric P. Prostko
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Current environmental and economic concerns have increased public and producer interest in reducing herbicide inputs through integrated weed management. A field experiment was conducted near College Station, TX, to evaluate an integrated johnsongrass [Sorghum halepense (L.) Pers.] management system in cotton (Gossypium hirsutum L.) using reduced rates of clethodim [(E,E)-(±)-2-[1-[[(3-chloro-2-propenyl)oxy]imino] propyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one] and cultivation. Clethodim broadcast at 1.0X (140 g ha-1), 0.75X, or 0.5X rates with and without cultivation was compared with clethodim at the same rates in a 50% band over the row plus cultivation. Cultivation did not improve johnsongrass control or cotton yield when clethodim was broadcast. Johnsongrass control was less in 2 of 3 years and cotton yield less in 1 of 3 years in systems with clethodim banded plus cultivation compared with clethodim broadcast with no cultivation. Greater than 90% control was obtained by clethodim at the 0.5X rate applied to four- to six-leaf stage johnsongrass under good growing conditions. Control by clethodim at the 0.5X rate was reduced if application was delayed until johnsongrass had seven or more leaves. No differences in johnsongrass control or cotton yield occurred with clethodim at 0.75X or 1.0X rates. The results demonstrate that johnsongrass can be controlled and production costs reduced by timely broadcast application of clethodim at below-labeled rates.