Tank Contamination

What is the possible impact on peanut of tank contamination from Dicamba and 2,4-D?
By Sarah Berger, graduate student, and Jason Ferrell, Extension Weed Specialist, University of Florida

Producers currently battling glyphosate-resistant weeds are eagerly awaiting the release of dicamba- or 2,4-D-tolerant soybeans and cotton. This technology has the potential to greatly improve control of troublesome broadleaf weeds. But, what about the impact on peanuts?

Though great strides have been taken and application restrictions will be in place to manage drift of dicamba and 2,4-D, improper tank cleanout or simply spraying the wrong field is still a valid concern. Both herbicides can significantly injure peanut and cause yield reduction. So what is the potential danger of application of dicamba or 2,4-D on peanut?

Early Exposure, Severe Injury
Research has shown that peanuts are quite sensitive to dicamba, even when rates are low. In general, the earlier dicamba is applied after peanut emergence, the more severe peanut injury the crop may experience.

Typical symptoms of dicamba injury are curling around leaf edges and general twisting and malformation in stems and leaves.

A 16-ounce per acre rate of dicamba on peanut can lead to 92 percent injury and 85 percent yield loss. Applications at this rate will result in the death of many peanut plants. Though a rate of 16 ounces per acre might seem high, failure to flush the lines after a dicamba application could result in this high of a rate being seen for the first 50 feet or so into the peanut field. Lower rates across the whole field are more likely if the tank is simply not emptied between fields. However, even at rates as low as 1 to 4 ounces per acre, a 29 to 48 percent reduction in yield is likely.

Lack Of Visual Damage Misleading
The effects from 2,4-D misapplication are not as severe as that of dicamba. Applications on younger plants, at around 30 days old, will have a much greater impact on yield than applications on 60- day old plants.

Typical 2,4-D injury on peanut is twisting and curling of leaves and stems. Injury symptoms on peanut will often appear, but then the plant will show recovery within a few weeks and no further symptoms will be evident, even at rates up to 16 ounces per acre. But, this lack of visual symptoms can be misleading. Although the peanut plants appear to have recovered from the 2,4-D application, it is common for flowering and peg formation to be greatly reduced for a longer period of time. This is why a three percent foliar injury can result in 36 percent yield reduction.

Complete Tank Cleanout Necessary
Dicamba and 2,4-D resistant crops is a powerful new technology that has the potential to provide many positive benefits for crop producers. However, be fully aware that a high standard for tank cleanout is more important than ever. The significance of cleaning 2,4-D out of sprayer when going from peanuts to cotton is well known. Now, producers will need to ensure that they use the same techniques before spraying peanuts.

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