Control of Canada Thistle by Soil Fumigation without Tarpaulins

Abstract

Three years of field experiments showed that Canada thistle. [Cirsium arvense (L.) Scop.] could be controlled with deeply injected soil fumigants without covering the soil with a tarpaulin. The degree of control depended on the kind of fumigant, the rate of application, and the depth of injection. Weed control with fumigants usually improved as the rate of application and depth of injection increased. The most effective treatment was 1,3-dichloropropene at 560 kg/ha injected to a depth of 46 cm. Good to excellent control of Canada thistle was also obtained with 1,3-dichloropropene at 280 kg/ha injected either 23 or 46 cm and ethylene dibromide at 160 kg/ha and chloropicrin + ethylene dibromide at 20 + 55 kg/ha injected at 46 cm. Results with ethylene dibromide and chloropicrin + ethylene dibromide were more erratic than with 1,3-dichloropropene. Increasing the percentage of chloropicrin in the combination reduced the control of Canada thistle.