Management of Canada thistle (Cirsium arvense) with repeated tillage, smother cropping and allelopathic cover cropping

Canada thistle is a perennial, creeping weed that is particularly troublesome to organic farmers. The challenge presented by this weed is due to its extensive underground storage tissues, which allow shoots to regenerate following tillage. In some cases, three years of repeated tillage, at greater operational and environmental expense, may be required to deplete these reserves and eradicate an established colony.

A three-year experiment will evaluate the effects of repeated tillage, smother crops, row crops and allelopathic cover crops on dense populations of Canada thistle (Cirsium arvense L.). In addition to evaluating these operations, the experiment will compare the potential of different sequences of these operations to control Canada thistle.

Repeated cultivation will occur every three weeks during the growing season. Cultivations will begin either in early May, or in late June. The later starting date is included in response to previous studies that suggest that early shoot growth is largely fueled by carbohydrate reserves. Thus, shoots that are allowed to bud (but not set seed) before the first cultivation will deplete carbohydrate reserves more than shoots that are tilled sooner. Smother crops will include buckwheat (Fagopyrum sagittatum Gilib), cowpea (Vigna unguiculata L Walp.) and pearl millet [Pennisetum galucum (L.) R.Br.]. All three species can be planted in mid- to late-June, which allows shoots to bud before being tilled under. More traditional crops will include corn (Zea mays L.), soybean (Glycine max L.), oat (Avena sativa L.) and alfalfa (Medicago sativa L.). Fall cover crops will include winter rye (Secale cereale L.), winter wheat (Triticum aestivum L.) and oilseed radish (R. sativus var. Oleiferus).

Researchers:

Don Wyse, University of Minnesota Department of Agronomy and Plant Genetics

Funding:

USDA – CREES