Weed Response to Atrazine and Alachlor Combinations at Low Rates

Early postemergence application of atrazine [2-chloro-4- (ethylamino)-6-(isopropylamino)- s -triazine] at 0.28 kg/ha in combination with alachlor [2-chloro-2′,6′-diethyl- N -(methoxymethyl)acetanilide] at 0.42 kg/ha plus a non-toxic oil-surfactant blend gave season-long weed control in sweet corn ( Zea mays L. var. rugosa ‘Seneca Chief’). Bioassay with oats ( Avena sativa L.) showed no detectable atrazine residue in the soil 3 months after herbicide application. In greenhouse studies, the response of Japanese millet ( Echinochloa crus-galli L. Beauv. var. frumentacea ) to early postemergence application of atrazine and alachlor combinations plus an oil-surfactant blend was synergistic. Soil uptake played a major role in the activity of the herbicides. Formulants used in commercial alachlor when added to atrazine spray, enhanced atrazine activity in a way similar to that of the non-toxic oil-surfactant.