Biologically Effective Dose and Selectivity of SAN 1269H (BAS 662H) for Weed Control in Corn (Zea mays)

Field experiments were conducted in 1996 and 1997 at five locations in southwestern Ontario to develop dose-response curves for SAN 1269H (SAN 835H plus dicamba) for weed control and crop tolerance in corn. SAN 1269H controlled wild buckwheat (Polygonum convolvulusL.), common ragweed (Ambrosia artemisiifoliaL.), common lambsquarters (Chenopodium albumL.), pigweeds (Amaranthus retroflexusL. andA. powelliiS. Wats.), barnyardgrass [Echinochloa crus-galli(L.) Beauv.], and yellow foxtail [Setaria glauca(L.) Beauv.]. Biologically effective doses of SAN 1269H (BAS 662H) were 440, 430, 180, and 40 g/ha for yellow foxtail, barnyard grass, wild buckwheat, and common ragweed, respectively. The biologically effective dose (that which provides 90% reduction in weed dry matter) for common lambsquarters was 560 g/ha when SAN 1269H was applied preemergence (PRE) and 110 g/ha when applied postemergence (POST). When applied PRE at a rate of 420 g/ha, pigweed was controlled, whereas only 85 g/ha was required when applied POST. Grain yield increased with dose of SAN 1269H and did not differ with time of application. Temporary crop injury was observed when SAN 1269H was applied at the four- to six-leaf growth stage. Optimum corn yields were achieved with doses of 100 to 250 g/ha.