I travel our tri-state region a lot. In my travels last summer, I’ve got to tell you, I saw too many weed escapes. If we’re going to gain the upper hand in the fight against resistance, we must figure out how to manage these escapes.
The first step is to add pre-emerge herbicides to your weed management toolbox this spring. A pre-emerge herbicide has multiple advantages for your weed management program. PRE’s add residual control that reduces the weed seed bank and allows for early crop growth to establish a canopy before weeds emerge. PRE’s also bring another Mode of Action (MOA) to your program. Having multiple effective MOAs in your program greatly reduces the development and spread of weed resistance.
With the majority of our corn and soybean acres in Roundup Ready technology, glyphosate resistant weeds are today’s primary weed concerns. The glyphosate resistant weeds present in the Dakotas and Minnesota include horseweed, kochia, common and giant ragweed, and waterhemp.
Of these weeds, glyphosate resistant kochia is the most concerning. Even if you use multiple modes of action to keep weeds in check, or have not yet encountered resistance issues on your farm, be on the lookout for kochia, as it can be windblown from neighboring fields. Two or three kochia plants rolling across your ground in the fall can deposit many seeds that you will need to address the following year.
Waterhemp is another problem weed in our region. Because waterhemp emerges later in the growing season than other weeds, PRE’s may not be able to effectively control it. The PREs we use provide about four weeks of control, which is ideal with a thin canopy in a crop’s early stages. However, open canopy areas later in the season can be an issue and allow for later waterhemp germination. Using a residual-type product, similar to Warrant, in our POST applications may be beneficial to provide longer season activity to control late emerging weeds.
LibertyLink soybeans or corn are a great alternative to glyphosate, and are another tool for managing weed resistance. They are not the final answer though, and I recommend using PRE’s with all of your LibertyLink acres as well. Liberty does not have the same ideal spraying window as Roundup, but applying a PRE will provide more flexibility for applying Liberty during its recommended window.
The battle against resistant weeds is on, and will continue to be a concern for growers in the northern plains as more glyphosate resistant weeds move into our region. Increasing the number of modes of action within a field minimizes the chances for resistance to develop. Using all of your weed management tools this spring, beginning with PRE’s, will help you succeed in preventing weed resistance.