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Four studies were conducted at the LSU AgCenter Rice Research Station near Crowley, Louisiana to evaluate the effects of simulated herbicide drift on Cocodrie rice. Herbicides were applied at 6.3 and 12.5% of the labeled usage rate of 863 g ae/ha of glyphosate, 70 g ai/ha of imazethapyr, 493 g ai/ha of glufosinate, and 44 g ai/ha of imazamox. Herbicides were applied to rice at the 1-tiller, panicle differentiation (PD), boot, and physiological maturity growth stages. Spray volume varied proportionally to herbicide dosage and was 15 L/ha for the 6.3% rate and 29 L/ha for the 12.5% rate using 234 L/ha as the target spray volume and were applied with a tractor-mounted CO2-pressurized sprayer. Glyphosate reduced plant height and primary and total crop yield, with the greatest reduction in primary crop yield resulting from glyphosate applied at boot. Primary crop rice seed germination was reduced by glyphosate. Glyphosate reduced ratoon crop rice seed weight; however, ratoon crop seed germination was not reduced. Imazethapyr reduced plant height and primary and total crop yield, with the greatest reduction in primary crop yield resulting from imazethapyr applied at boot. Primary crop rice seed weight was reduced by imazethapyr applied at boot. Primary crop rice seed germination was reduced by imazethapyr. Ratoon crop rice seed germination was reduced by imazethapyr applied at PD. Glufosinate reduced rice plant height and, when applied at boot, reduced primary and total crop yield. Primary crop rice seed germination and primary crop seedling vigor were reduced by glufosinate. Imazamox reduced plant height and primary and total crop yield with the greatest reduction in yield observed from rice treated at boot. Primary crop rice seed germination was reduced by imazamox. Primary crop seedling vigor was reduced with imazamox applied at boot. Ratoon crop rice seed weight and germination was not affected by imazamox. Simulated glyphosate, imazethapyr, glufosinate, and imazamox drift applications did not affect rice when applied at maturity. The greatest reduction in primary crop yield was observed when glyphosate, imazethapyr, glufosinate, and imazamox were applied to rice at boot and they all reduced primary crop rice seed germination. |
