Q&A: Understanding residual control with preemergence herbicides

With soybean fields planted, albeit late in a lot of cases, many farmers and retailers may be wondering how long the preemergence herbicides they applied will hold against tough weeds. It’s an important factor to consider when planning for any potential postemergence herbicide     applications.

Recently, a soybean retailer submitted a timely question via Operation: Clean Fields around expected residual control of a top preemergence herbicide. Chad, a retailer in Minnesota, asked the question, and Jeff Moon, market development specialist with Corteva Agriscience, answered.

Q: When applied as a preemergence, how long of a residual can I expect using Sonic® herbicide?

A: Sonic herbicide has a labeled application rate of 4 to 7 ounces per acre. The length of residual will depend greatly on where your application falls within that rate spectrum. If you apply 4 ounces per acre, you can expect residual control to last between four and six weeks. From there, as a general rule of thumb, you can expect an additional seven to 10 days of control for every ounce per acre that the application rate increases. So, at the maximum rate of 7 ounces per acre, we’ve seen seven to 10 weeks of residual control when applied as a preemergence.

One benefit of that long-lasting residual control is it gives farmers a much wider window to make postemergence applications. It also keeps those later-season weeds small and easier to control, so you can stay on label with planned postemergence treatments.

Of course, both the amount of moisture received after application as well as the soil type can factor into the duration of residual control experienced.

For more information about Sonic, talk with your local Corteva Agriscience territory manager or visit BattleWeeds.com.

soybean field

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