HERBICIDAL CONTROL OF CIRSIUM-ARVENSE (L) SCOP ROOTS AND SHOOTS IN NO-TILL SPRING WHEAT (TRITICUM-AESTIVUM L)

Three herbicide treatments were applied each year over a period of 4 years to Cirsium arvense (L.) Scop. infestations in no-till spring wheat (Triticum aestivum L.) in North Dakota, USA. Both chlorsulfuron at 30 g ai ha-1+a non-ionic surfactant and a mixture of clopyralid+2,4-D at 70+280 g ai ha-1 gradually reduced Cirsium arvense shoot density, root biomass, and adventitious root buds over the 4-year treatment period in two trials. These two treatments did not merely induce adventitious root buds to become dormant. They virtually eliminated roots to a depth of 50 cm by year 4. Tribenuron methyl at 10 g ai ha-1+a non-ionic surfactant was less effective in reducing shoot density and root biomass.