Entering into the first part of May, a small percentage of the overall corn acres in Indiana have been planted. As growers get into the field, their minds are often thinking ahead to the next part of the growing season. Now is the time to start thinking about post-emerge application for your corn.

“The ideal timing for post-emerge application in corn is when weed size is five to six inches or less,” said Mike Carrell, Ceres Solutions Agronomy Branch Manager. According to Carrell, AnswerPlot and various university data shows that yield reduction can start when weeds are four inches or taller. “It’s imperative to reduce yield loss by checking weed height, not corn height, to determine time to early post spray.”

Post emerge application treatments vary depending on if you used a pre-emerge herbicide.  If one wasn’t applied, then you’ll need to control grass and broadleaf weeds through a total post-emerge program application. If you did use a pre-emerge, you should consider post-emerge applications for escapes and to add additional control for late emerging weeds. Studies have shown that pre-emerge application herbicides don’t provide complete protection against tough to control broadleaves including giant ragweed, waterhemp/Palmer Amaranth, and morning glories.

Corn in the V4 to V5 stage is the ideal timeframe to spray. “When the corn is this small, we can get a good coverage of the herbicides on the weeds through a broadcast application.” Waiting much after that, Carrell says, makes it hard to get the coverage down to the weeds.

If a grower does wait until the corn is too tall, methods can be taken to make the application, but the effectiveness drops as the machines aren’t designed get complete coverage below the canopy.

“Timing is important for both weed control and yield preservation,” said Carrell.

Carrell also suggests utilizing post-emerge application on every field. “To achieve your field’s potential, every acre needs to be sprayed.” According to Carrell a 2-pass program is proven to deliver better control.

“The overall benefit of doing a post-emerge application of herbicides is to allow corn to reach its maximum yield potential,” said Carrell. “Controlling these weeds early on allows corn to grow without competing for moisture and crop nutrients.”

Let Ceres Solutions help you with your corn acres! Talk to your local agronomy branch to set up your post-emerge application today.