Soybean varieties differ in tolerance to Sharpen herbicide, says study

sprayer maintenance
Photo courtesy United Soybean Board

Soybean varieties differ with respect to levels of tolerance or sensitivity to saflufenacil. Alabama Extension specialists have researched and recorded soybean varietal responses to saflufenacil applications for the past two years, in hopes of helping producers make informed decisions about application timing and impacts.

Saflufenacil

A group 14 protoporphyrinogen oxidase inhibitor (PPO) herbicide, saflufenacil is an active ingredient in several commonly used herbicides, including Sharpen, Integrity, Verdict and Op-Till.

Tyler Sandlin, an Extension crops specialist in the Tennessee Valley, says the chemistry provides excellent burndown control of marestail/horseweed and other broadleaf weeds in soybeans when used properly.

“Good coverage and a methylated seed oil (MSO) are required for optimal performance,” Sandlin says.

Soybean varietal sensitivity

A varietal response is typically seen when an application is made immediately prior to planting a sensitive variety, followed by rainfall when the germinating seeds are absorbing water or cracking the soil surface.

In this case, the herbicide is also absorbed into the seed or comes in contact with the hypcotyl when it is emerging. Sandlin said poor closure of the seed furrow, especially on conventionally tilled soils with a heavy rain event following application and planting, can also contribute to injury.

2018 varietal screening results

Sandlin and Dr. Dennis Delaney, Extension Soybean Specialist, found an in-field screening of commonly planted soybean varieties to be a valuable tool. Delaney and Sandlin screened 38 soybean varieties in 2018. Findings are based on silt loam soils.

While knowledge of sensitivity is important, awareness of fully tolerant varieties is very important. Rates were chosen accordingly. Plots were replicated. Untreated running checks were also present throughout the trial.

Sandlin says it is important to note these results are visual results observed at one location under one set of conditions. More or less injury may be observed under different conditions, as environmental conditions can have a tremendous impact on the level of observed sensitivity.

Download the printable report in its entirety.

Alabama Cooperative Extension System contributed this article.

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