I don't do corn but these things work well on weeds that are close to crop if you want to apply Roundup without a garden-sized spray bottle.

http://cgi.ebay.co.uk/Red-Weeder-Wiper-stick-weed-killer--incVAT_W0QQitemZ230346306970QQcmdZViewItemQQimsxZ20090601?IMSfp=TL090601142003r20346

Basically a PVC hockey stick with a big wick for part of the blade.  We've got a few of something that looks identical to these things.  Not sure if they've the exact same company though.  The only trouble we have is with the clear plastic elbows breaking at the joint.