Evaluation of glufosinate for the control of red rice (Oryza sativa) in commercial rice (Oryza sativa)

Abstract

Research was conducted in 1996 and 1997 to 1) evaluate weed management systems in transferrin 'Gulfmont' rice with glufosinate, 2) evaluate the tolerance of selected red rice ecotypes to glufosinate at different application rates and growth stages, and 3) to determine the optimum growth stage and rate of glufosinate applications for red rice control. Field studies showed that all single applications provided excellent early season control of broadleaf signalgrass, barnyardgrass and common purslane when applied alone at either the 1- to 2- or the 4- to 5-leaf stage. In addition, all split applications of glufosinate resulted in at least 95% control of the grasses and common purslane throughout the season. Standard commercial treatments that contained glufosinate gave significantly higher control than those without glufosinate throughout the season. Glufosinate, however, was relatively poor on yellow rutledge in 1996, ranging from 5 to 30% at all stages and single rates. Split applications of propanil followed by glufosinate were poor in 1996 for yellow rutledge control, but in 1997 control increase to 95% by 28 days after treatment (DAT). Field studies conducted to evaluate application rate and timing of glufosinate for red rice control indicated that excellent red rice control could be achieved by all applications regardless of growth stage. Greenhouse studies conducted to evaluate Texas red rice ecotype response to glufosinate in the spring indicated that there was a significant ecotype by rate interaction at 14 DAT at the 1- to 2-leaf stage. Of the five most tolerant ecotypes selected in the spring, three were located in counties adjacent to each other and the remaining two ecotypes were found in adjacent counties. A comparison between location of the most tolerant ecotypes and commercial rice acreage in Texas, indicated that the ecotypes were collected from the major commercial rice producing areas. Greenhouse studies conducted during the spring showed that the only significant difference in rate occurred at 21 DAT at the 1- to 2-leaf stage. The summer data indicated that at 14 and 21 DAT there was a significant difference between 0.6 and 1.2 kg ai ha⁻¹ rates of glufosinate for all growth stages.