Sheryl, do they do aerial spraying of the crops? That could be your answer. Aerial spraying gets a lot more than just the field crop they are spraying. There's over-spray & a lot of drift involved too & woods aren't likely to be much exempt from the spray coming down through the canopy; if for no other reason than when it lands on the foliage & then the dew (or rain) drips off the foliage it ends up on the under story plants.
