Reducing Herbicide Injury to Sorghum with Crop Protectants

Greenhouse and field studies were used to evaluate crop protectants with herbicides in order to obtain selective, broad-spectrum weed control in sorghum [ Sorghum bicolor (L.) Moench ‘RS 626’]. Of the herbicides evaluated alachlor [2-chloro-2′,6′-diethyl- N -(methoxymethyl) acetanilide] was the only one causing sorghum injury that could be moderated with crop protectants. The crop protectant anhydride (1,8-napthalic anhydride) was most effective in reducing alachlor injury when applied as a seed treatment at 0.5% (w/w). Storage of anhydride-treated seed for 1 year did not increase anhydride damage to sorghum seedlings. Preplant applications of alachlor, incorporated into the soil, caused four times more injury to sorghum than did the same rate applied preemergence. Combinations of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)- s -triazine] and alachlor did not increase sorghum injury or alter the effects of the crop protectants. In the field, anhydride was the most effective crop protectant used. Crop protectant R-28725 (2,2-dimethyl-3-dichloroacetyloxazolidine) at 0.5% w/w to sorghum seed and at 0.6 kg/ha as a tank mix was effective in reducing sorghum injury at the lower alachlor rates. Crop protectant R-25788 ( N,N -diallyl-2,2-dichloroacetamide) was the least effective of those studied; however, seed treatment at 0.5% w/w was more effective than the tank mixes.