There is not enough information here. When they say they were "dusted" by the planes, were the planes at low, crop-dusting altitude, or up high? Did it look deliberate, or were the planes maybe simply "clearing the tubes" as they flew by? (Not likely in my mind--sounds a little fast and loose with fertilizers or pesticides even for a real cropduster).

Most cropdusters I have seen in the Valley were either orange or yellow, and have an extremely weird and distinctive shape that even a city boy like me recognizes as a cropduster.

This may be a tempest in a teapot, or it may have been some kind of "dry run" by a terrorist, although you would think such things would take place far from any human habitation to avoid being seen.

Don't forget the stunt pilot who got in trouble for practicing her "smoke stream" in front of uninformed people.