Cutleaf teasel (Dipsacus laciniatus L.) is an invasive plant that is spreading through natural and disturbed areas. Teasel grows for two or more years as a rosette which stays green late in the growing season and begins growth earlier in spring than its native competitors. The purpose of this study was to find a time both seasonally and in cutleaf teasel’s life history when herbicides could be applied to decrease teasel with the least impact on the surrounding vegetation. We tested the effects of three different herbicides (glyphosate (Round-UpTM), triclopyr amine (GarlonTM), and clopyralid (LontrelTM)) on cut and uncut teasel at three different times of the year (July and October 2005, and April 2006) near Clinton Lake in Dewitt Co. Illinois. Photosynthetic measurements were taken before application to determine teasel’s susceptibility to the herbicides, and we harvested seed heads and rosettes in late October 2006. Results indicated teasel was photosynthetically active at all three application times. Cutting before herbicide application had no significant effect on the number of seeds produced or the dry weight of the rosettes. Herbicide treatment in April significantly reduced the amount of seeds produced, but there were no significant differences among the three herbicides. Clopyralid application in April significantly reduced rosette biomass, but none of the herbicides significantly affected rosette biomass at the other two times. Our studies suggest herbicide application early in the growing season may be beneficial in controlling the spread of teasel, and that mowing at the time of spraying will not increase effectiveness of the herbicide.
 P. A. Werner, “Colonization Success of a ‘Biennial’ Plant Species: Experimental Field Studies of Species Cohabitation and Replacement,” Ecology, Vol. 58, No. 4, 1977, pp. 840-849. doi:10.2307/1936219
 O. D. Cheesman, “The Impact of Some Field Boundary Management Practices on the Development of Dipsacus fullonum L. Flowering Stems, and Implications for Conservation,” Agriculture Ecosystems and Environment, Vol. 68, No. 1-2, 1998, pp. 41-49.
 B. G. Rector, V. Harizanova, R. Sforza, T. Widmer and R. N. Wiedenmann, “Prospects for Successful Biological Control of Teasels, Dipsacus spp., a New Target in the United States,” Biological Control, Vol. 36, No. 1, 2006, pp. 1-14. doi:10.1016/j.biocontrol.2005.09.010
 D. J. Bentivegna and R. J. Smeda, “Cutleaf Teasel (Dipsacus laciniatus): Seed Development and Persistence,” Invasive Plant Science and Management, Vol. 4, No. 1, 2011, pp. 31-37. doi:10.1614/IPSM-D-10-00026.1
 M. K. Solecki, “Cut-leaved and Common Teasel (Dipsacus laciniatus L. and D. sylvestris Huds.): Profile of Two Invasive Aliens,” In: B. McKnight, Ed., Biological Pollution: The Control of Impact of Invasive Exotic Species,” Indiana Academy of Science, Indianapolis, 1993, pp. 85-92.
 L. F. Huenneke and J. K. Thomson, “Potential Interference between a Threatened Endemic Thistle and an Invasive Nonnative Plant,” Conservation Biology, Vol. 9, No. 2, 1995, pp. 416-425. doi:10.1046/j.1523-1739.1995.9020416.x
 B. Glass, “Vegetation Management Guideline: Cut-Leaved Teasel (Dipsacus laciniatus L.) and Common Teasel (Dipsacus sylvestris Huds.),’” Natural Areas Journal, Vol. 11, 1991, pp. 213-214. doi:10.1890/04-0840
 M. P. Dudley, J. A. D. Parrish, S. L. Post, D. G. Helm, and R. N. Wiedenmann, “The Effects of Fertilization and Time of Cutting on Regeneration and Seed Production of Dipsacus laciniatus (Dipsacacae),” Natural Areas Journal, Vol. 29, No. 2, 2009, pp. 140-145. doi:10.3375/043.029.0206
 R. Hobbs and L. F. Huenneke, “Disturbance, Diversity, and Invasion: Implications for Conservation,” Conservation Biology, Vol. 6, No. 3, 1992, pp. 324-337. doi:10.1046/j.1523-1739.1992.06030324.x