Be Aware of Grapes and 2,4-D Drift

Chris Boerboom, Extension Weed Scientist

The potential for herbicide drift is an issue every good applicator monitors and manages by using the best that equipment technology and drift reducing agents can offer. However, some herbicides and crops create challenges that are extremely difficult to manage. One example is grapes and 2,4-D. This is a concern in certain regions of Wisconsin because grape vineyards are either an established or expanding crop. The potential sources of 2,4-D can be from 2,4-D used in burndown applications to field crops, 2,4-D applications to pastures, or even 2,4-D applications to lawns. The 2,4-D can move either as spray particles in wind or as vapors. With spray particles, the direction is dictated by the wind, which can be predicted. However, vapor movement is more difficult to predict as vapors may move in different directions as air currents change during the many hours after the 2,4-D application.

Grapes are naturally highly sensitive to 2,4-D and the symptoms depend on the dose. The symptoms will be expressed on the new growth where new leaves are developing (figure 1). The most frequent symptoms are probably the “fingering” that develops along the leaf margin (figures 2 and 3). Higher doses can cause more severe damage and stunting. 

Figure 1. 2,4-D symptoms on grapes appear on new growth.

Figure 2. “Fingering” symptomology appearing along the margin of a grape leaf along with leaf distortion.

Figure 3. Minor “fingering” symptomology appearing along the margin of a grape leaf.

Photo credits: J. Colquhoun

Grapes are a high value crop and every effort should be taken to reduce the risk of causing injury. The first key step is to know the location of vineyards in the region where 2,4-D is being used. Second, if burndown applications need to be made near a vineyard, alternate products should be used such as straight glyphosate, paraquat, or other tank mix partners to replace 2,4-D. The question of an appropriate setback distance for 2,4-D also needs to be considered. There are no fixed guidelines provided on labels or restrictions provided by state or federal agencies. The “safe” setback distance will depend on wind direction and speed, air temperature, topography, acres treated, application equipment, etc. A mile setback may be appropriate in certain situations. In other cases, this distance could be reduced. An applicator will have to use their best judgment, but be aware of the potential for injury and the associated liability.