Glyphosate is typically used in conjunction with "Roundup Ready" crops, or before/during planting in "no-till" crops. While Monsanto developed a Roundup Ready line of wheat, it never actually made it to market, AFAIK, so why would you be spraying glyphosate on wheat?

(Serious question; while I have some background in agriculture, I'm not familiar with all of even the common practices.)

ETA: Reading the Snopes link, looks like it's mainly practiced in North Dakota, which explains why I've never heard of it.