Ethan Carter, Regional Crop IPM Agent, Jay Ferrell, and Ramon Leon, UF/IFAS Weed Speciaslits
2017 will be a landmark year for row crop agriculture, as several long awaited herbicide technologies have finally been released by the EPA to help farmer’s combat troublesome herbicide resistant broadleaf weeds. Two dicamba products are available, one from Monsanto (Xtendimax™ with VaporGrip Technology™), another from BASF (Engenia™) and one 2,4-D product courtesy of Dow (Enlist Duo® with Colex D® Technology). Xtendimax was the first product approved by EPA back in November, followed by Engenia last month, and more recently Enlist Duo®. Although approved by EPA, we are still eagerly awaiting approval for the dicamba herbicides (Xtendimax and Engenia) from the Florida Department of Agriculture.
These new herbicides will be primarily used in crops that are naturally susceptible to dicamba and 2,4-D, but that have been engineered to tolerate them and prevent negative impacts on yield. Unlike traditional dicamba and 2,4-D formulations, each of these new herbicide products are specifically designed to minimize volatility and the risk of drift. It is imperative to read each product label carefully, as they have numerous restrictions regarding their use. As additional crops are approved, labels will be amended.
Xtendimax and Engenia are new formulations of the herbicide dicamba that have low drift and volatility potential. Xtendimax is currently labeled for use in Xtend™ soybeans and cotton, and Engenia is labeled for dicamba tolerant (DT) corn, cotton and soybean. The formulation for Enlist Duo is a combination of glyphosate and 2,4-D choline with very low volatility and the capacity to reduce the proportion of driftable fine droplets produced during application. Enlist Duo is also registered for Enlist™ corn, cotton, and soybean. Both Xtendimax and Engenia are group 4 herbicides, while Enlist Duo is a combination of group 4 and 9.
Herbicide Resistance Management
These new herbicides will be used to manage glyphosate resistant (GR) and ALS resistant (ALS-R) weeds such as Palmer amaranth (Amaranthus palmeri). However, they do not have the flexibility in application timing and uses that glyphosate had when GR crops were introduced. For these reasons, in order to regain control of GR and ALS-R weeds, farmers will have to monitor weed growth more closely to treat weeds when they are less than 4 inches tall. Treating larger weeds not only will provide poor control and multiple escapes, but more importantly it will likely favor the evolution of dicamba and 2,4-D resistant weeds. If this happens, producers will again lose important tools to manage troublesome weeds in crop fields. The labels of all these three new herbicides, Enlist Duo, Engenia, and Xtendimax, will have specific requirements to monitor escapes and to report suspected cases of resistance to manufacturers.
Dicamba and 2,4-D are herbicides that can cause injury to a very wide range of broadleaf plants from vegetables to ornamentals and fruit crops. Despite the decreased risk of spray drift associated with these new product formulations, farmers will need to be more vigilant than ever concerning spraying conditions and where sensitive crops are relative to their position. Open communication with neighbors regarding their crops is very important. Even if they are growing cotton or soybeans, one should not assume that their crop is dicamba or 2,4-D resistant.
All three products have different restrictions regarding buffer zones, application time relative to crop growth, wind speed, weed height and other factors. Another important change with these new herbicides is that, due to the extensive set of requirements for application, labels will refer to websites you will have to visit in order to determine which nozzles, tank-mixes, and parts for sprayers comply with the label. These new herbicides cannot be sprayed with conventional flatfan nozzles. Their labels require specific anti-drift nozzles and pressure ranges. Similarly, tank-mixes will only be permitted for products that have been pre-tested by manufacturers, because some agrichemicals, when tank-mixed with these new herbicides, can impact the capacity of their formulations to reduce drift and volatility. Even after extensive review, the label specifications for these anticipated products will be unique. The state labels will likely be more restrictive than the federal labels; therefore, it is imperative that producers obtain a copy of the Florida label and follow it explicitly.