Herbicides that work as growth regulators include 2,4-D, dicamba, picloram, aminopyralid, and clopyralid. Some of these can be very persistent in soil, manure, and compost.
The following photos are from four different gardens in Washakie County. The most likely causes of contamination for these gardens:
1. Spray drift (presumably 2,4,-D)
2. Aminopyralid used to spray thistles the year before (when the area was in pasture)
3. Manure from animals fed hay harvest from a field sprayed with aminopyralid or clopyralid
4. Grass clippings from a lawn sprayed with 2,4-D right before it was mowed