Evaluation of some herbicides for controlling weeds in the rice nurseries of Mazandaran.
In field trials conducted in Mazandaran during 1989-90, the effects were evaluated of molinate at 4.2 kg/ha, butachlor at 2.4 kg, thiobencarb at 3 kg and oxadiazon at 0.48 kg applied 2 d before sowing (DBS), molinate + propanil at 2.8 + 2.8 kg and propanil at 4.2 kg applied 20 d after sowing (DAS), and thiobencarb and molinate applied 15 DAS for weed control in rice. The most problematic weeds were Scirpus spp. and Echinochloa crus-galli. All herbicide treatments reduced the number of Scirpus spp. and E. crus-galli plants/m2 from untreated control values of 23 and 29, resp., to 2-21.3 and 0-1, resp. Butachlor resulted in slight damage to the rice seedlings and oxadiazon resulted in complete necrosis and death of the seedlings; all other herbicide treatments showed no phytotoxicity to the rice seedlings.