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Spring is in the air! The grass is greening up, the songbirds are back serenading us, each day is getting longer, the daily temperature is sort of warming up, and snow is changing to rain (for the most part). But that is the problem, isn’t it? Temps are staying lower than average, and the precipitation does not seem to want to stay away for longer than a 48-hour stretch, at best. In Champaign, the average temperature for the month of April so far is about 10 degrees cooler than average. With the rain we have received and lack of drying it is leaving farmers antsy to get to work, specifically field work!

The average planting time for soybeans throughout the state falls between mid-April to early May. Prior to planting, a few critical passes need to be made through the field, such as a spring burndown herbicide application to kill the winter annual weeds and any early emerging spring annuals. Burndown refers to the herbicide application made prior to planting to kill winter annuals such as henbit, chickweed, purple deadnettle, etc. Non-selective herbicides are used such as glyphosate, 2,4-D, metribuzin, gramoxone, etc. to kill the gambit of weeds found in the spring.

But back to the wet weather – where does that leave those spring burndown applications? How critical are they and how does this year’s weather impact them? When looking at the calendar, those burndown applications should have been made or are going out soon. Not this year though - everyone is waiting for the weather to turn drier to make them, which leaves the weeds free to grow. Luckily, though, with the wetter weather it has also been cooler holding the weeds back from turning last year’s corn fields into a winter annual jungle, full of purple and yellow flowers. Control of these weeds is critical; the cleaner a field is from the beginning of the year, the easier it is to maintain through the growing season.

Not only is the weather contributing to a challenging start for the 2022 growing season but so are the supply concerns, especially when it comes to herbicides that will be utilized for multiple passes on a field. For example, glyphosate is heavily used in both burndown applications as well as in postemergence passes. With tight supply, the herbicide needs to be utilized where it will be the most effective and maximized to the highest potential of activity. The ability to respray fields will be much more challenging and costly this year due to the supply concerns. Starting off with a clean field is key to maximize season long weed control.

For traited soybean varieties, other herbicides such as dicamba or 2,4-D can control weeds in POST passes if there is only enough supply of glyphosate for the burndown application. As always, but even more important this year, for effective weed control the sprayer needs to be set up for optimal coverage – ensuring the proper nozzles, volume, pressure, and speed are all used. Reach out to your agronomic advisor to ensure that weed species and active ingredients match up.

Another tool to help maximize weed control is through adjuvant programs. Think of the adjuvants that are tank mixed with the herbicides to represent a three-legged stool – a stool that holds up the herbicide efficacy. Each of the legs represent one of the following, in the tank, in the air, and on the leaf. Water conditioners impact what happens to the herbicide when it is in the tank, drift and deposition aids control the herbicide when it is in the air, and surfactants or oils help to get the herbicide on and into the leaf. When each of these “legs” are balanced, it will help to conserve the amount of herbicide used and improve the efficacy.

Between the weather and tight supply of herbicides, 2022 is off to an interesting start, but these two barriers will not stop the burndown applications from being made. A more conscience effort will have to be put forth to maximize weed control, making the kill after one pass. Starting the growing season with a clean field will set the stage for the weed control for the rest of the year, making it a very critical pass.

Sources:

https://stateclimatologist.web.illinois.edu/data/champaign-urbana/

https://www.kygrains.info/blog/2022/1/17/considerations-for-spring-burndown-strategies-when-herbicides-are-in-short-supply