Varietal Tolerance of Rice (Oryza sativa) to Bromoxynil and Triclopyr at Different Growth Stages

Abstract

This study was conducted to determine the tolerance of three cultivars of rice (‘Lemont’, ‘Mars', and ‘Tebonnet’) to bromoxynil and triclopyr. The effects of two rates of application (the labeled rate and twice the labeled rate) at three different growth stages (two- to three-leaf stage, four- to five-leaf stage, and panicle initiation) on percent visible injury rating and percent grain yield reduction of rice were investigated. Percent visible injury ratings for triclopyr averaged across all rates and application times, were 15, 16, and 25% (LSD = 3%) for Tebonnet, Mars, and Lemont, respectively, whereas ratings for bromoxynil were 11, 8, and 7% injury (LSD = 2%). Tebonnet was more tolerant than Lemont to triclopyr with an average percent grain yield reduction, across treatments, of 6% compared with 9% for Mars and 12% for Lemont (LSD = 4%). Bromoxynil did not decrease the average yield of any of the three cultivars.