Safety evaluation of benzobicyclon 25% SC on rice varieties at different leaf stages

Benzobicyclon is a 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide that was registered in Chinese rice production. It has a wide herbicidal spectrum, especially good control efficacy on malignant weeds such as resistant Chinese sprangletop (Leptochloa chinensis), weedy rice (Oryza sativa f. spontanea), and so on. In order to explore the application prospect and technology of benzobicyclon in the direct seeding rice field, the safety evaluation of benzobicyclon 25% SC on various rice varieties at different leaf stages was studied by the pot-culture experiment. The results showed that: Under whether the condition of shallow water at 1-2 leaf stage, 2-3 leaf stage, and 3-4 leaf stage of rice, or the wet condition at the 1-2 leaf stage of rice, the application of 150-375 g a.i./hm² of benzobicyclon 25% SC was safe to the three conventional Japonica varieties Nanjing 46, Huruan1212, Songxiangjing1018 and the hybrid Japonica varieties Shenyou 26, which were mainly planted in Shanghai, and had no significant effect on the growth indices including plant height, aboveground fresh weight, root length, and root fresh weight. The results indicate that benzobicyclon is safe for Japonica rice varieties, and is expected to become an excellent herbicide variety in the direct seeding rice fields with the updated application technology.