Application strategy of 25% benzobicyclon SC in controlling weedy rice

Weedy rice (Oryza sativa f. spontanea) is a kind of rice with weed characteristics that harms rice production. Screening herbicides that can control weedy rice will effectively solve the problem of chemical control. In order to explore application strategy of 25% benzobicyclon SC, in different dosages, time and methods to control weedy rice, and safety to rice were studied by potted experiment. The results showed that 25% benzobicyclon SC had high herbicidal activity to weedy rice. Compared with the poisoned soil method, spray application had the advantages of fast acting speed,excellent control effect, wide use period and high safety to rice. After using 25% benzobicyclon SC 150-375 g a.i./hm² on weedy rice in germination stage, needle leaf stage, 1-2 leaf stage and 2-3 leaf stage respectively, the control effect of spray method on weedy rice reached 98.0%-100%, 94.0%-100%, 94.0%-100% and 83.0%-100%, but poisoned soil method was 51.0%-100%, 56.0%-93.0%, 27.0%-89.0% and 28.0%-71.0%. Under the dosage of 187.5 g a.i./hm² and 375 g a.i./hm² of 25% benzobicyclon SC, spraying application had no adverse effect on growth indexes of rice, but poisoned soil method had inhibition on rice plant height, root length, root and plant fresh weight. The efficacy of the benzobicyclon appears slowly, and the best control effect is generally achieved 20-30 days after herbicide application. The optimal control period of weedy rice should be from its germination stage to 1-2 leaf stage, spraying method, and recommended dosage was 150-187.5 g a.i./hm². If benzobicyclon SC is used during the 2-3 leaf stage of weedy rice, the dosage should be increased to 187.5 to 225 g a.i./hm². The water layer of 1-2 cm should be established and maintained at least 5 days when benzobicyclon SC was applied.