Rice Crop Response to Simulated Drift of Imazamox

Abstract

Field studies were conducted near Crowley, LA, to evaluate the effects of simulated herbicide drift on ‘Cocodrie' rice. Each treatment was made with the spray volume varying proportionally to herbicide dosage based on a spray volume of 234 L ha−1and an imazamox rate of 44 g ai ha−1. The 6.3%, 2.7-g ha−1, herbicide rate was applied at a spray volume of 15 L ha−1and the 12.5%, 5.5-g ha−1, herbicide rate was applied at a spray volume of 29 L ha−1. Rice was treated at the one-tiller, panicle differentiation, boot, and physiological maturity growth stages. Injury was observed with imazamox applied at the one-tiller timing. Injury was not observed until 21 and 28 d after treatment (DAT) when imazamox was applied at the panicle differentiation and boot timings. The greatest reduction in plant height resulted from applications at the one-tiller timing at 7 and 14 DAT; however, when evaluated at harvest, plant height was reduced no more than 10%. Imazamox, averaged over rate, applied to rice at the boot timing reduced primary crop yield 66% compared with the nontreated. Applications at the boot timing resulted in an increased ratoon crop yield; however, the yield increase did not compensate for the loss in the primary crop yield.