Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
A few calls have come in this week about control of Italian/annual ryegrass in corn. In all the situations, glyphosate was used early, and the ryegrass plants did not die, and folks are looking for options. We had a number of fields sampled last year and tested with glyphosate and we did not detect resistance. Most of the cases from this year involved applications at least a few weeks ago when the weather was still cool AND/OR multiple herbicides in the tank at the time of application. I am recommending retreating with glyphosate. The growing conditions are much improved from last month and glyphosate is now performing much better on Italian ryegrass.