Editor’s Note: Late in the week, the Ninth Circuit Court of Appeals voided the registration for dicamba-based herbicides used with related seed trait technology. The products included Engenia, Xtendimax and FeXapan.
Plenty of questions are swirling around about how this might effect herbicide strategies this season during periods when growers can still apply the products. The following is a response Dr. Steve Li, Alabama Extension Weed Scientist, to questions that farmers and crop advisors are asking him.
His responses only apply to Alabama and, as he notes, this is a fluid situation and requirements or restrictions are subject to sudden change.
Here are the questions and his responses.
#1. Status of Enlist?
Several growers called me about Enlist, and if this is part of the ban. So far, Enlist One or Enlist Duo can still be sprayed on resistant crops without further restrictions. Liberty plus Enlist One followed by Liberty or Roundup plus Enlist One are great treatments on pigweed with some size, based on our data from last 3 years.
#2. What is the status of dicamba technology in Alabama?
The Alabama Department of Agriculture and Industry (ADAI) issued an order within the state of Alabama that Engenia, Xtendimax and FeXapan distribution and application can continue until they receive further instruction from EPA. This could change at any moment, though.
#3. What about Tavium?
Tavium is the only formulation containing dicamba that was not banned by the Ninth Circuit Court. Worst case scenario, if EPA issues a ban on other new dicamba formulations, we still have a horse in the race that is great for Palmer management.
Tavium is a premix of Xtendimax plus Dual Magnum, so growers should expect more leaf burn than Xtendimax alone. But the residual control from S-metolachlor (Dual Magnum) will be very beneficial to Palmer and annual grass control. Leaf burn from Tavium will be similar as Xtendimax plus Dual magnum in a tank mix.
#4. What about leaf burn?
I have been asked about leaf burn on cotton and peanut a lot. There is no rule of thumb on this matter since environmental conditions and spray timing play a critical role.
Hot and dry conditions usually cause worse burn that lingers for a while, which we have seen in previous trials. Sometimes, spraying in cool morning may result in less burn than in hotter late afternoon. However, reliably predicting leaf burn is not feasible, just like we cannot predict yield loss by visual injury after dicamba drift.
All four group 15 herbicides (Warrant, Dual Magnum, Outlook and Zidua) have some potential to burn crops, and it is hard to say which one will constantly burn more than the others. They are structurally similar chemicals.
The leaf burn potential from Tavium should be similar to Xtendimax plus another group 15 herbicide when applied over the top of cotton. With recent rain and more heat, I do not think leaf burn from these group 15 herbicides will be a big concern compared to in a hot and dry summer.
#5. Can you piggyback acephate with dicamba?
Another common questions these day is adding acephate with dicamba application to save a trip. Sometimes, growers want to use too much product in one pass. I am not a big fan of tank mixing Roundup and Dicamba and acephate and a Group 15 herbicide (or Tavium) plus surfactant in the same tank.
I have seen more than 40% leaf burn in my field trials with similar tank mixes. It is better to break up these chemicals into two passes to give cotton some time to catch it breath before it is burned again.
If someone has to spray all of these chemicals in the same trip because too many fields need to be sprayed, I do not expect a serious risk for yield loss. But it is possible that in some cases cotton maturity will be delayed for one to two weeks because of leaf burn and injury recovery.