This week, Alberta Agriculture & Forestry’s Scott Meers noted painted lady butterfly larvae (Vanessa cardui). The larvae are important to scout for because this species feeds on a wide range of host plants including soybean (Action threshold=>25% defoliation), sunflowers, borage and dry beans in addition to several species of thistles (including Canada thistle) and mallow.
The “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” includes photos of both the larvae and adult. The guide is available as an English-enhanced or French-enhanced version. The Butterflies and Moths of North America website tracks confirmed sightings of V. cardui (screenshot provided below; retrieved 30May2019).