By Jeremy Ross, Extension Soybean Agronomist
With the widespread reports of off-target herbicide injury, I’ve had numerous phone calls about replanting damaged fields or the use of foliar products to recover from the herbicide injury. Many of the fields that I have walked or seen via text message received damage prior to reproduction. From research data conducted by Dr. Tom Barber (Dicamba Drift and Potential Effects on Soybean Yield), the developmental stage where the highest yield reduction was observed from drift rates of dicamba for MG IV soybean varieties was the R1 growth stage. Treatments applied to growth stages earlier than R1 showed less yield reduction (10% or less). From a three year project looking at maturity group, planting date, and latitude, the yield reduction from the maximum yield potential for a MG IV planted on July 1 in NE Arkansas is 35% and SE Arkansas is 23%. Based on results from these two studies, replanting this late in the season would potential have a greater yield reduction than keeping an herbicide-injured soybean field. The two unknown factors on many of these damaged fields is the amount of product in the off-target drift and how many events these fields have experienced. Dr. Barber’s data shows higher rates of dicamba cause greater yield reduction, but very little, if any data is available about the yield reduction on multiple off-target events.
My program has looked at several research trials examining foliar-applied products trying to maximize soybean yield. However, we have not evaluated any of these products under simulated herbicide drift situations. I polled several colleagues in surrounding states, and no one has any data to support the application of foliar products to soybean to reverse the effects of off-target herbicide damage. Some are looking at these products and their effect on yield in herbicide damage plots, but this data will not be available until this fall. As I mentioned above, we have looked at a number of these products in the best conditions to maximize soybean yield, and have not seen an economical benefit from these products. Recommendations for these damaged fields for the rest of the growing season are to continue to manage them like the drift event had not occurred, and try to eliminate any other stresses. Continue to scout these fields for insect and disease pressure, and spray the appropriate pesticide when economic thresholds are met for these pest. Also, irrigate in a timely manner to avoid any drought stress.