Results and impacts of the application of Stinger (clopyralid) herbicide to native and non-native plants.
A Listserv conversation from August discussed the application of the herbicide clopyralid (Stinger). The herbicide was used to target several weeds in the Asteraceae family, primarily prickly lettuce (Lactuca serriola) and sowthistle (Sonchus arvensis), but also other prominent weeds in the Aster family. Two separate trials were documented, one by Matt Blakeley-Smith of Greenbelt Land Trust and another by Joe Buttafuoco of The Nature Conservancy in Oregon. The trials occurred in early June of 2014, broadcast spraying a 30 acre prairie in one trial and 40 acre prairie in the other. The 40 acre prairie was a former agricultural field that was seeded with a diversity of native grasses and forbs the previous fall. Both contributors noted that while Stinger did damage the targeted plants, it was often not successful in killing them outright. Buttafuoco noted that many of the plants were flowering approximately 4 weeks after application, including unwanted weeds. Blakeley-Smith commented that Lactuca serriola was damaged the most and had not gone to seed as of his posting. Overall, he was happy that the herbicide stopped the targeted Lactuca serriola from going to seed and did not damage native plantings. Ideally the herbicide application would have taken place in April when the targeted species are most susceptible to clopyralid, but weather and contractor availability resulted in a delayed application which resulted in intermediate control.