Postemergence Herbicide Sprays in Corn

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.

impact of callisto alone vs with atrazine on weed control

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