Efficacy of herbicidal control methods on common teasel (Dipsacus fullonum L.)
Common teasel (Dipsacus fullonum L.) has become an aggressive invasive species throughout most of North America, invading roadsides, ditches, rights of way, pastures, and natural areas. This study examined three herbicides used to control common teasel: 1) BK 800, a 2,4-D based broad-leaf herbicide mixed in diesel fuel; 2) Glyphomax® a non-selective glyphosate-based product mixed in water with 5 mL/L of a non-ionic surfactant (Nu-Film®-IR) added; and 3) Transline®, a clopyralid based broad-leaf herbicide used for non-crop areas with 5 mL/L of the Nu-Film®-IR. The herbicides were applied in three concentrations taken directly from the label specifications: the low end, the high end, and the midpoint between the low and high ends. Plant rosette counts taken two weeks after application were compared to counts taken earlier to create a "survival ratio." The majority of the applications resulted in total kill of all common teasel rosettes. Ratios were compared among all treatment groups and the control. All herbicide treatments resulted in significantly (p<0.001) more kills than the control. The different concentrations of each treatment were compared against each other to determine the optimum concentration for common teasel control. The 2 mL/L concentration of Transline®, the 13 mL/L concentration of Glyphomax® and the 55 mL/L of BK 800 were the most effective treatments. There was no significant difference among the efficacies of the three above herbicides. This study provides the first known quantitative study of herbicidal control of common teasel, and it should serve as a starting point for future studies on controlling this invasive plant.