Click on the following link for an article from the official blog of the Association of American Law Schools - Agricultural Law Section about a significant pesticide drift ruling from the Minnesota Court of Appeals: Johnson et al. v. Paynesville Farmers Union Cooperative Oil Co. The Johnsons, organic farmers, sued the PFUC over allegations that pesticide and herbicide spray had drifted onto their organic crops and caused crop damage (including the alleged loss of organic certification).
PFUC applied for summary judgment to have the claim thrown out on the basis that there was no "trespass by particulate matter". A lower court judge agreed with the PFUC, but the appeal court ruled that pesticide overspray could constitute an unlawful entry (trespass). The AALS article notes that most jurisdictions now recognize agricultural chemical drift as sufficient grounds for a claim in trespass.