Efficacy of increasing application rates and combination of herbicides and mowing at different growth stages of common teasel (Dipsacus fullonum)

Abstract

AbstractCommon teasel is a troublesome invasive weed in North and South America. Additional information on the efficacy of herbicide application and mowing at different growth stages will help in common teasel management. First, an outdoor pot experiment was performed to assess the effects of increasing application rates and combinations of glyphosate and 2,4-D amine when applied at the 4-leaf, rosette, and bolting stages. Second, field experiments were performed to evaluate the impact of time of cutting on invasive common teasel height, head number, and head length. Finally, germinability of seeds collected from naturally growing plants was determined to evaluate the feasibility of mowing invasive common teasel after flowering. Only glyphosate applied at 1.08 kg ae ha−1 at the 4-leaf stage provided adequate control (>90%). Although control was not satisfactory (<90%) when applying glyphosate at 2.16 kg ae ha−1 at the rosette and bolting stages, and 2,4-D at 1.75 kg ai ha−1 at 4-leaf stage, significant injury and biomass decline were observed. Glyphosate and 2,4-D combinations did not improve common teasel control compared with single applications of each. Cutting rosettes strongly reduced inflorescence production (34%–49%) and cutting flowering plants prevented total regrowth. Germination of seeds averaged 14% when harvested 10 d after flowering, and maximum seed germination (>90%) occurred 30 d after flowering. Glyphosate applied alone at the recommended commercial rate early in the growing season, together with cutting at the flowering stage, may be the most beneficial way of controlling invasive common teasel.