Regarding the potential to move rust around, Tom Allen - Mississippi State plant pathologist - sent this to his email list earlier in the month:

They claimed to be students, but upon a call to the university several hours after they left it was learned that no one existed on the graduate student rolls by those names. To this day no one knows why this happened, or who it was that collected the leaves. Should ANY of you be contacted by someone claiming to be a student (or other person interested in collecting rust infected leaves) or requesting to receive rust infected soybean leaves please have them contact me.

Before anyone receives infected material I expect to receive a WRITTEN request from the principal investigator on the project and not only the reason for rust infected leaf collections but desire to know what kind of project these samples are being collected for. If samples are to be sent to anyone through the mail they must be accompanied by the proper USDA-APHIS-PPQ permit which will allow the interstate movement of plant pests. These permits are not only VERY specific, but numbered so that they can be verified with the proper agencies. I would greatly appreciate it if anyone should contact you from within the state or outside of MS to please put them in touch with me directly.

While I know that essentially anyone could go to a field that was infected or find a field on their own, and then collect samples, I want to limit this from occurring by making you aware of the situation that occurred in the past and let you know how I plan on reacting when and if this occurs now or in the future. I do not have a problem collaborating/cooperating with anyone, but want to know who wants the samples and for what purpose. Personally, I believe this is a fair way to respond to the situation.