Several years ago I received an ag related grant to buy a microscope to use for identifying pollen 
floral sources in my pollen traps and honey. 

long story short in a normal non-drought season in central Mn we found minimal traces of corn 
pollen for a period of 2 weeks. 

this region is rich with pollen and nectar sources from early April to late Sept and we average some 
nice crops. corn is a fairly common crop here although maybe not as densely planted as southern MN 
or IA etc..  so while I don't worry much about my bees eating corn pollen here it could be a much 
different story elsewhere. 

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