CANADA THISTLE (CIRSIUM-ARVENSE) CONTROL IN NO-TILLAGE CORN (ZEA-MAYS)

Canada thistle control in no-tillage com was studied in Western Maryla nd from 1990 to 1992. The best treatment at planting for controlling C anada thistle was a tank mixture of 2240 g/ha glyphosate plus 560 g/ha 2,4-D. Clopyralid applied at 210 and 280 g/ha alone and 106 g/ha tank mixed with 560 g/ha 2,4-D effectively controlled Canada thistle in no -tillage com (85 to 96%). Nicosulfuron applied at 35 g/ha and 20 or 40 g/ha primisulfuron suppressed Canada thistle (59 to 75%). Tank mixtur es of nicosulfuron or primisulfuron with 2,4-D or dicamba generally in creased Canada thistle control (75 to 87%) compared with control by th ese herbicides applied alone. Treatments that controlled Canada thistl e generally increased com yields compared with the weedy controls. Yie ld increases were most dramatic in 1991 when precipitation was low.