Causes of Low Control Effect of Pre-emergence Herbicides against Cocklebur (Xanthium canadense Mill.)
Jin-Won Kim1,* Yun-Ho Jeon1 Hyun-Woo Jeong1
1Crop Protection Division, National Institute of Agricultural Sciences, RDA, Wanju, 55365, Korea
Burweed (Xanthium canadense Mill.) is exotic weed and one of problematic weeds in orchards but many pre-emergence herbicides cannot control this weed effectively. The objective of this study was to clarify low control effect of 10 pre-emergence herbicides and to find the cause. As a result of 10 pre-emergence herbicides application to soil sowing X. canadense seeds with seed coat, dichlobenil was the best as 100% control followed by oxyfluorfen and simazine. Residual oxyfluorfen and simazine in above-ground part were less than 20%, but those in seed coat were more than 80% compare to those in the soil. Xanthium canadense without seed coat was well-controlled by both herbicides. Therefore, the cause of low performance of pre-emergence herbicides against X. canadense was that thick seed coat absorbed herbicide and the penetration was insufficient to control X. canadense, not the tolerance. Application of non-selective herbicides or cutting could be more appropriate for control of X. canadense in the orchards rather than application of the pre-emergence herbicides.
Figures & Tables
Fig. 1. Pretreatment of Xanthium canadens seeds for even germination.