That implies intent on the owners part. I think the property owners should treat it no differently than if the patent holder/experimenter spilled 1000 gallons of dieldrin or DDT on their property.
It is an “unauthorized release”, not only that, but of an unapproved product. As the patent holder, and as it is not approved for release, Monsanto clearly is the responsible party for the contamination and liable for full mitigation costs.
Monsanto has better lawyers than farmers