The Importance of Pre-Emergence Herbicides

Mason Lewis
Sales Agronomist, Grinnell, IA

Every year in early spring, farmers across the state of Iowa attempt to prepare the perfect seedbed to plant their corn and soybeans into. There are various methods of preparation, but all farmers try to get their soil in the best condition and maintain a weed free environment for their crop. The various methods include turning over the soil with tillage, terminating existing cover crops, or applying a pre-emergence herbicide to the soil, just to name a few.

Today’s focus is the importance of applying a pre-emergence herbicide as the foundation of your weed control system in 2022.The first rule in weed control management is to start clean and stay clean. Whether that be with tillage or the proper burndown program, make sure your field is weed-free at the time of planting. The next step is applying a pre-emerge herbicide to the soil. This is important because it’s a lot easier to kill weeds while they’re still below the soil surface than when they emerge. When choosing a pre-emerge herbicide, select one that has long lasting residual and that controls both grasses and broadleaves with multiple modes of action. Picking the correct pre herbicide will drastically reduce the pressure put on the post application by eliminating tough to control weeds before they break the soil surface.

With the current market inflation, the price of all pre-emerge herbicides has increased and yet the availability has decreased. This has led farmers to question the cost and need of these herbicides. Over the last few months there have been some changes to both the labels of the Roundup Ready® Xtend and Enlist® weed systems that highlight the importance of pre herbicides. Last year, the label for XtendiMax® herbicide stated that you could spray up to R1 or June 30^th in Iowa, whichever came first. The new regulations, however, state that you can spray XtendiMax® herbicide up to R1 or June 20^th in Iowa, whichever comes first. The same can be said for the Enlist® system. Last year, you were able to spray through R2. This year the label has changed to through R1. This has essentially knocked 7-10 days of spraying soybeans off of the calendar, compared to last year. The new label changes also make it difficult for us to come back in for a second post trip and clean up the fields because we won’t have enough time. This supports the need for a good pre herbicide to help reduce the amount of weeds that are in the field for our post herbicide pass.

Pre-emerge herbicides are the foundation of a great weed control system. They help keep fields clean and maintain the efficacy of our post herbicides. Even with the cost increasing and the availability decreasing in 2022, pre herbicides are important or even more important than previous years. The new label changes on the XtendiMax® and Enlist® herbicide labels will reduce the amount of days for post spraying soybeans, so it is essential to have a pre herbicide down in front of our post pass to eliminate those tough-to-kill weeds.

This market might be tough but Key is here to talk through your weed management options. Reach out to your local Key agronomist for herbicide questions or guidance.