After several decades searching for tools to control red rice, imidazolinone tolerant rice was developed to selectively control red rice. To better understand this technology An experiment was conducted in 2004/2005, in Santa Maria, Rio Grande do Sul, Brazil to evaluate: 1) red rice control by imidazolinone herbicides in Clearfield™ rice; 2) evaluate the imidazolinone herbicide carryover effect on rygrass and non-tolerant rice (IRGA 417) and 3) evaluate the outcrossing rates between Clearfield rice and red rice. The experimental design was a randomized block design, with 3 treatments and 12 replications. To determine the outcrossing rates between Clearfield rice and red rice, virtually all the red rice panicle was collected and analyzed in the area. The carryover effect was tested using ryegrass and a non-tolerant rice cultivar (IRGA 417). The herbicides tested controlled red rice. Although injury to Clearfield rice was observed, the herbicide did not affect yield. Herbicide carry-over to non-tolerant rice was observed, reducing plant stand on rice seeded 361 days after herbicide application. Natural out-crossing occurred between Clearfield rice and red rice, at rates of 0.065%.
IRGA 422 CL; imazethapyr; imazapic; persistence
