Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
A couple of thoughts and reminders on postemergence spraying in corn. Our options for postemergence control fall into a few herbicide groups:
glyphosate (Roundup)
glufosinate (Liberty)
HPPD herbicides, or Group 27 (i.e. Callisto, Impact, Laudis)
ALS herbicides, or Group 2 (i.e. Accent Q)
dicamba, or Group 4 (i.e. Status, DiFlexx)
atrazine
There are many premixes out there with these active ingredients. Be sure to read the labels on application timing and rates.
HPPD herbicides have gained a lot of popularity as a postemergence spray, but remember they should be tanked mixed with atrazine. If they are not tank mixed with atrazine they are much less effective as a postemergence application. If corn is too tall for atrazine application, that often means the weeds are tall as well, further reducing the effectiveness of the HPPD herbicides. If weeds over 4 inches tall and corn is too tall to include atrazine may want to consider an alternative herbicide.
