atty. gen. john ashcroft says to beware of "suspicious looking cropdusters." now. yes. well. okay.

what exactly is a suspicious looking cropduster? how does it differ from its innocuous-looking brethren? (and aren't all cropdusters a bit funny looking? to those who live outside the plain states, at least?) is it the plane itself? or is it the context? for example: if i were to see a cropduster in new york city, regardless of the character of the man flying and despite his potentially noble intentions, i would find that suspicious. is this what he means then? i am utterly at sea on this one.