Strategies for controlling Cirsium arvense in organic crop production

Kurzfassung

Abstract - Three strategies for controlling Cirsium arvense including (1) repeated stubble tillage with subsequent forage crop cultivation, (2) repeated mowing of a grass-clover ley, and (3) forage crop cultivation following a grass-clover ley ploughed in May/June were investigated in field experiments over 3 years. The development of C. arvense shoot density was regularly assessed on subplots with defined thistle densities. In the medium-term (9 months), repeated stubble tillage (treatment 1) decreased shoot density of C. arvense more effectively than a once mowed grass-clover ley (2). However, after 22 months, treatments 1 and 2 resulted in a similar strong reduction of C. arvense shoot density of 95 % and 97 %, respectively. At this time, the efficacy of treatment 3 was lower (89 %), however, not signifi-cantly different to that of treatments 1 and 2. After 26 months, the effect of all treatments was still appar-ent; however, the efficacy of treatment 3 was signifi-cantly lower than that of treatment 2. Generally, the different strategies showed only minor differences, thus delivering options for optimal strategies of this-tle control under given specific conditions of site and cropping systems.