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 sout hwestern Ontario to develop dose-response curves for SAN 1269B (SAN 835H pl us dicamba) for weed control and crop tolerance in corn. SAN 1269B controll ed wild buckwheat (Polygonum convolvulus L.), common ragweed (Ambrosia arte misiifolia L.), common lambsquarters (Chenopodium album L.), pigweeds (Amar anthus retroflexus L. and A. powellii S. Wats.), barnyardgrass [Echinochloa crusgalli (L.) Beauv.], and yellow foxtail [Setaria glauca (L.) Beauv.]. B iologically effective doses of SAN 1269B (BAS 662H) were 440, 430, 180, and 40 g/ha for yellow foxtail, barnyard grass, wild buckwheat, and common rag weed, 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 postemer gence (POST). When applied PRE at a rate of 420 g/ha, pigweed was controlle d, whereas only 85 g/ha was required when applied POST. Grain yield increas ed with dose of SAN 1269H and did not differ with time of application. Temp orary crop injury was observed when SAN 1269H was applied at the four- to s ix-leaf growth stage. Optimum corn yields were achieved with doses of 100 t o 250 g/ha.