Activity of benzobicyclon herbicide in common Louisiana rice production practices

Abstract

A study was conducted at the LSU AgCenter H. Rouse Caffey Rice Research Station (RRS) to evaluate benzobicyclon herbicide application timing on water-seeded rice. Benzobicyclon was applied at seven different timings, at 246 g ai ha-1 in a water-seeded rice production system. Benzobicyclon controlled ducksalad above 90% when applied into the pinpoint flood. Barnyardgrass control was greater than 90% from applications made on pegging rice and immediately following pinpoint flood establishment. At 49 days after treatment (DAT), yellow nutsedge control exceeded 90% following benzobicyclon treatment with a pegging rice or pinpoint flood timing. Ducksalad control was greater than 90% following application into the pinpoint flood. A study was conducted at the RRS and LSU AgCenter Northeast Research Station (NERS) to evaluate nine different rates of benzobicyclon on weeds common to Louisiana rice production. Benzobicyclon was applied at 0, 31, 62, 123, 185, 246, 493, 739, 986, and 1232 g ha-1. Barnyardgrass, yellow nutsedge, and false pimpernel did not exceed 50% control, regardless of benzobicyclon rate. At 42 DAT, benzobicyclon applied at 185 and 246 h ha-1 controlled purple ammannia and Indian toothcup, respectively, and this control was similar to control observed with 986 to 1232 g ha-1 of benzobicyclon. At the conclusion of the study, no differences in fresh weight biomass occurred for barnyardgrass, yellow nutsedge, purple ammannia, or false pimpernel. Benzobicyclon applied at 246 g ha-1 reduced ducksalad and Indian toothcup biomass 87 and 77%, respectively. A glasshouse study was conducted at the LSU campus in Baton Rouge to evaluate five rates of benzobicyclon applied into a 5- or 10-cm flood. Benzobicyclon applied at 246 g ha-1, in either flood depth, reduced yellow nutsedge tuber development and growth. Tuber production is the primary means of yellow nutsedge reproduction in the southern US, and use of this herbicide could impact future nutsedge populations. A field study was conducted to evaluate benzobicyclon in mixture with imazethapyr or imazamox in imidazolinone-resistant rice. The addition of benzobicyclon increased activity on hemp sesbania over imazethapyr or imazamox; however, hemp sesbania control did not exceed 30% when treated with any herbicide mixture.