Spraying with 2,4-D can be harmful to dicamba-tolerant cotton and spraying with dicamba can cause injury to 2,4-D-tolerant cotton, resulting in yield and economic losses for the cotton producer.
In other words, no cross-tolerance exists between these two technologies, and injury can occur in the wrong circumstances.
Is there a way to “heal” injured plants?
In the webcast “Efficacy of Recovery Sprays to Auxin Injury on Cotton,” James Griffin – a Texas A&M Ph.D. student – summarizes two studies from 2018 and 2019 that addressed that question. Griffin evaluated the effectiveness of available commercial products to recover cotton plants from reduced dicamba and 2,4-D rates when injured at first-bloom stage.
Researchers compared numerous sprays by assessing the amount of injury and recovery as well as combined lint yields and average boll counts.
The news, at least from this batch of research, isn’t good.
No recovery treatments were able to regain yields compared with untreated plots for either 2,4-D or dicamba. Numeric yield gains were shown for almost no recovery sprays over the auxin-only treatments. The trends were inconsistent, at best, from year to year.
This 6-minute presentation is available through the “Focus on Cotton” resource on the Plant Management Network.