Grapes are among the list of very sensitive high-value crops grown in Pennsylvania, and drift damage often incurs very high costs. Therefore, field crop applicators should stay aware of the risks associated with 2,4-D drift. Below, we explain the issues surrounding drift to 2,4-D sensitive crops and list some essential points for applicators to keep in mind next spring.
As we continue to hear more and more cases of dicamba drift cases across the mid-South, it's important to remember that drift happens close to home too. Last week we heard of several claims of alleged 2,4-D drift damage in commercial vineyards in Pennsylvania. The growers believe these likely came from 2,4-D applications on nearby field crops during spring burndowns, and some damage was reportedly severe enough to kill all or part of this year's wine grape crop. Still, for field crop growers, 2,4-D remains an important option for managing problem weeds like marestail, especially in the face of herbicide resistance. Therefore it is important to follow the label when applying 2,4-D to reduce drift potential to other sensitive crops grown throughout the state. This article outlines 2,4-D label guidelines and explains how and when applications are most likely to affect off-target crops.
In addition to grapes, other 2,4-D-sensitive high value crops in Pennsylvania include sweet potatoes, tobacco, peppers, tomatoes, melons, squash, and brassicas. In vegetables, the product often becomes unmarketable once the plants show visual herbicide damage. Grapevines present an additional challenge as a woody perennial crop - herbicide damage weakens the permanent plant tissue, which can translate into decreased yield and poor grape quality for several years. According to Mike White, an Iowa State University viticulture specialist who has been responding to 2,4-D drift reports on vineyards for years, vines can be damaged by 2,4-D drift as soon as the plant leafs out in the spring. Therefore, 2,4-D drift has the largest effect on grapevines when it's applied between April and May - by this point, leaves are present and grape clusters are forming. Since this coincides with an important time for 2,4-D burndown in field crops, care should be used when applying 2,4-D burndowns in fields near vineyards.
In the case that off-target drift is confirmed, monetary consequences to the applicator can be high due to the high per-acre value of many of these sensitive horticultural crops. Land owners whose fields experience drift are able to file complaints with the state department of agriculture, which then investigates the claim to determine the source.
Here are some points to consider when applying 2,4-D, to prevent drift to sensitive crops:
- Timing and awareness - It is not always feasible to time applications in a way that avoids sensitive periods for off-target crops. However, it is useful to be aware of when nearby sensitive crops are most susceptible to damage, as well as when they are being planted.
- Many vegetables are most susceptible during flowering, but they can be damaged any time after transplant or emergence. Tomato injury often occurs May-early June.
- With grapevines, drift injury can occur any time after their leaves emerge but is often the worst (and will cause the highest yield loss) from April-June. Drift later in the season will have less effect on this year's crop, but can largely lower the plant's ability to survive the winter.
- Buffers - For fields adjacent or near to non-target crops, larger buffers decrease injury potential. While 200-300 foot buffers are typically adequate, the safe buffer distance depends on other factors like wind speed and direction, air temperature, and topography. If applying the new dicamba formulations, check the label for specific minimum buffer requirements. Most 2,4-D and dicamba drift cases originate within 1/8 mile.
- Nozzles - Use nozzles that increase droplet size, and use lower spray pressures. Larger droplets decrease the risk for drift.
- Spray pressure - Low spray pressure also decreases the risk for drift
- Inversions and wind speed - Avoid spraying during temperature inversions. Inversions often occur in the evenings and are indicated by very calm wind speeds (under 2 mph) and warm temperatures. Inversions cause herbicide particles to hover in the air after application, then gradually move upward and drift onto neighboring areas. Do not spray 2,4-D or dicamba if wind speeds are under 2 mph or above 12 mph.
- Temperature - Avoid spraying during periods of several days of high temperatures. Off-target damage from volatilization may increase if temperatures are too high during application. The risk of volatilization is directly related to increases in air temperature, and most volatilization occurs within 2 days of application.
Dicamba and Soybeans Videos
On a closely related topic, you may want to check out these two new videos just added to the PA Soybean Board YouTube channel. In a case example, Dr. Bill Curran discusses Diagnosis of Soybean Injury from Dicamba Drift and Xtend Soybean Use and Precautions