Immediately contact Christian Krupke at Purdue University. (firstname.lastname@example.org
). They have a protocol that detects Clothianidin from bee, comb, etc at the parts-per-billion.
You can read the paper they published (2012) on real-world exposure to seed treatment talc dust at: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0029268
Document your impacts because 1) it is important to science, 2) may encourage solutions to the corn dust problem, 3) Bayer is under pressure to create a fund to pay for impacts to affected keepers and you want to preserve your claim.
The corn-dust issue is moving quickly, partly based on the European pressure. Even the generally skeptical Randy Oliver (http://gallery.mailchimp.com/5fd2b1aa990e63193af2a573d/files/What_Happened_to_the_Bees_This_Spring2013_opt.pdf
) says that corn dust must be dealt with immediately.