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Symptoms of dicamba exposure in soybean

Non-Xtend soybeans are extremely sensitive to dicamba. Recently published research found that exposure symptoms occurred in non-tolerant beans at rates as low as one twenty-thousandths of the 1x rate of 0.5 pounds of acid equivalent (ae) formulation per acre.

Understanding dicamba

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Symptoms: Dicamba exposure in non-tolerant soybean

Field observations of dicamba injury symptoms during 2017 ranged from cupping and strapping of newly emerged leaves to height reductions and injury to growing points.

What to look for if you suspect dicamba injury

  • Extreme cupping of trifoliolate leaves, which is most pronounced on the upper trifoliolates (Figure 2).

  • Veins of affected leaves tend to assume a parallel orientation instead of the usual net venation pattern (Figure 3).

  • Tips of cupped leaves with parallel veins are often brown- or cream-colored.

  • Plants are stunted compared to plants not demonstrating the above symptoms; these plants may sometimes remain stunted the remainder of the season (Figure 1).

  • Depending on time and dose of exposure, pod development can be adversely affected.

Photos: Dicamba injury symptoms

Xtend soybeans
Figure 1. Xtend soybeans (left) planted next to a non-Xtend soybean that’s showing dicamba injury symptoms. Photo: Liz Stahl.
Cupping of young trifoliate
Figure 2: Cupping of young trifoliate leaves following exposure to dicamba. Photo: Aaron Hager.
Veins of young, affected leaves
Figure 3: Veins of young, affected leaves assume a parallel orientation after dicamba exposure. Photo Aaron Hager.

Other causes of leaf distortions

Other leaf symptoms may mimic dicamba injury. As previously mentioned, dicamba exposure symptoms can vary according to the dose of exposure and stage of soybean development. However, the symptoms of low-dose exposure tend to be fairly consistent.

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Jeff Gunsolus, Extension weed scientist

Reviewed in 2018

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