Dicamba Injury Assessment

Soybeans continued to show how sensitive they are to dicamba this summer. The characteristic puckered leaf symptom was widely evident.

Does visual injury mean yield loss? Not always, says University of Missouri Extension weed specialist Mandy Bish. It depends on the timing of the incident and the dosage.

University of Missouri studies show non-dicamba-tolerant soybeans in the R1 to R3 reproductive stage--beginning flowering to beginning pod set--sustain the greatest yield loss from drift events. Multiple exposures exacerbate losses, research indicates.

University of Missouri testing last year showed soybeans injured by dicamba in the V3 stage yielded similarly to noninjured beans after a single drift event. The dicamba rates used in the study simulated driftable rates of dicamba (not volatility).

Soybean plants in the R1 growth stage yielded 11 bushels per acre (bpa) less, and R3 yielded 7 bpa less than noninjured soybeans after a single drift event.

If soybeans sustained two drift events during the R1 and R3 stages, injured soybeans yielded 50% less than noninjured soybeans, according to Missouri research. Dicamba injury symptoms tend to take at least 10 to 14 days to appear.

Follow the latest from Pamela Smith, Crops Technology Editor, by visiting the Production Blogs at or following her on Twitter: @PamSmithDTN.


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