Phytotoxicity of Methazole to Prickly Sida and Cotton

The differential tolerance of prickly sida (Sida spinosaL.) and cotton (Gossypium hirsutumL.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione]was studied under greenhouse conditions. Methazole at dosages up to 8.96 kg/ha did not affect emergence of either species. Applications via nutrient solution, as well as preemergence and postemergence (over-the-top) treatments were phytotoxic to both species, becoming more pronounced with increasing concentration and time. However, a margin of selectivity between species occurred at dosages from 0.56 to 3.36 kg/ha preemergence. Directed sprays of methazole were not injurious to cotton. Selectivity would be influenced by plant size and method of application as well as biochemical differences between species.