The Interaction of Propanil+Thiobencarb with Imazethapyr and Imazamox for Enhanced Red Rice (Oryza spp.) Control in Imidazolinone-Tolerant Rice (Oryza sativa L.)

Recent observations from field systems suggest that RiceBeaux? may enhance efficacy of imidazolinone herbicides for control of red rice. Therefore, this research was undertaken to evaluate the herbicidal interactions of RiceBeaux? with Newpath? and Beyond?. Field experiments were conducted in 2012 and 2013 at the David R. Wintermann Rice Research Station in Eagle Lake, TX. In both years, imazethapyr alone and imazethapyr+RiceBeaux? treatments, were evaluated for control of XL723, which was used to simulate red rice in the field. In 2012, imazethapyr alone treatments provided 60 to 85% control of XL723 14 DAT and 87 to 100% control 21 DAT. Imazethapyr+RiceBeaux? combinations provided 51 to 91% control of XL723 14 DAT and 87 to 100% control 21 DAT. During both years, all treatments provided greater than 98% control of XL723 28 and 35 DAT.

In 2013, treatments that did not include a tank-mix with RiceBeaux? provided 60 to 77% control of XL723 14 DAT and 80 to 94% control 21 DAT. Imazethapyr+RiceBeaux? combinations provided 60 to 85% control of XL723 14 DAT and 81 to 99% control 21 DAT. These data indicated that for both years, Imazethapyr+RiceBeaux? combinations provided no additional control of XL723 compared to imazethapyr alone.

In 2013, experiments were conducted to evaluate the interaction of RiceBeaux? on imazamox in the field. Imazamox alone provided 62 to 75% and 87 to 94% control of XL723 14 and 21 DAT, respectively. Imazamox+RiceBeaux? treatments provided 57 to 85% control 14 DAT and 86 to 100% control 21 DAT. All treatments provided excellent control 28 and 35 DAT. Based on these data, imazamox+RiceBeaux? combinations provided no additional control of XL723 compared to imazamox alone.

Laboratory experiments were also conducted to characterize the interaction of RiceBeaux? on translocation and absorption of imazamox using ^(14)C-imazamox. TX-4 red rice plants were treated with ^(14)C-imazamox, with plants subsequently harvested at 8 separate timings. At each harvest timing, six samples were harvested from each plant and analyzed using Liquid Scintillation Spectrometry to quantify radioactivity.

Significantly more ^(14)C-imazamox was recovered from the cuticle when imazamox was applied alone, resulting in lower amounts of imazamox absorption. In contrast, imazamox+RiceBeaux? resulted in significantly higher absorption of ^(14)C-imazamox at 24, 48, and 96 hr after treatment. Results indicated RiceBeaux? may allow more imazamox to cross the lipophilic cuticle to reach the sites of action, which may result in enhanced red rice control. This interaction may explain the enhanced red rice control observed in field studies when RiceBeaux? tank-mixes were applied.