Lontrel (clopyralid) was initially registered in 1998 for environmental horticulture uses. This initial label contained an extensive list of environmental horticulture plants where Lontrel could be used without causing phytotoxicity. From 1985 to 2021, IR-4 examined 71 environmental plant species for phytotoxicity related to Lontrel applications. Of the researched crops, the following twelve can be added to the label at this time
The remaining seven crops that showed minimal or no injury are currently in the label. Forty-nine other species or genera treated with over the top applications exhibited minimal or no injury in the limited number of trials (one or two) for each crop.
Ten species or genera exhibited moderate to severe negative impacts, one of which is currently in the product label.