Spraying Near Vineyards and Nurseries

Spray drift is always a risk when spraying in the dynamic environment that we know as agricultural production outdoors. Wind, air temperature, soil temperature, relative humidity, water volume, nozzle type, nozzle size and operating pressure all influence the drift potential of your spray task. Even minute amounts of spray drift can seriously impact vineyards, orchards, nurseries and other multi-year crops. In some cases the drift damage may not kill the crop but adversely affect productivity for many years. If you don't do everything within your power to avoid spray drift in these situations - it will cost you.

Figure 1: 2,4-D injury in grapes

Two Types of Drift

There are two basic types of spray drift, namely particle drift and vapour drift. Particle drift is the movement of small droplets by wind or air currents to off-target locations. What we generally refer to as spray drift is actually particle drift. The potential for particle drift can be reduced by:

• Proper nozzle selection
  
• Producing larger spray droplets
  
• Using higher water volumes
  
• Minimizing nozzle-to-target distances
  
• Avoiding windy conditions
  
• Avoiding dead calm conditions
  
• Understanding spray droplet movement
  
• Reading the label
  
• Communicating with all parties involved

Every time you turn on your sprayer there is the potential for particle drift to occur. Particle drift can occur with all pesticides.

Vapour drift occurs when a product volatilizes or evaporates into the air. These vapours are carried downwind and could affect adjacent crops. Vapour drift is product specific. Certain products are known to volatilize in higher temperatures and cause damage. The volatilization of product could occur hours or days after the spray event. Before spraying, study the long term forecast to see what conditions are anticipated. See if these predicted weather conditions are suitable as post spray conditions on the product label .Your only methods of minimizing the potential for vapour drift are:

• Careful product selection, possibly switching to less risky herbicides
  
• Follow label directions completely to avoid problems
  
• Do not use volatile products
  
• Avoid spraying in hot, humid weather

Products known to have vapour movement include turf and lawn care herbicides, including 2,4-D and Banvel (dicambe)

Avoiding the Risk

Remember that grapes, orchards, and nursery stock are multi-year crops. Injuries caused by spray drift may inflict long term injury or adversely stress the plants affecting their health. This can lead to reduction in yield over longer periods of time. Experience has shown us that spray drift is not just a problem next door but may be separated by fields or farms. Drift can be deflected up and over by things such as topographic features, wind breaks and shelterbelts or other large man-made structures. In humid, cool and calm or near calm conditions, spray drift can flow downhill much like water. Spray droplets or product vapours carried in the air go where the air goes. Spray drift incidents are most often caused by particle drift and to a lesser degree vapour drift.

Spraying in the vicinity of multi-year crops requires special care. Avoiding the use of certain what we will refer to as nasty products means that the potential damage that might result from possible spray drift is significantly reduced. Some multi-year crops are ultra sensitive to glyphosate or 2,4-D based products. Product formulation may reduce the risk of volatization, eg. amine formulations of 2,4-D are less volatile than esters. The label will have cautionary application statements that should be followed. Look for restrictions on ambient air temperatures when spraying should be avoided. Contact the company representative to see what injury problems might be expected should drift occur onto a sensitive crop. It's worth your time to do a bit of homework to prevent drift before you spray rather than trying to figure out what happened after a drift incident.

Drift Investigations

In an effort to arrive at what or who injured an adjacent crop, the Ontario Ministry of the Environment can and may use tissue analysis as part of their investigation. The leaves of the injured crop are analyzed as well as the dead weeds of the suspect offending party. If the same product is detected in both and weather records point to your spray event, you might have some explaining to do. This is where your spray records really come into play. You may be asked to justify every decision you made regarding a particular spray event.

Next Steps

If you spray in the vicinity of grapes, orchards and nursery stock you need to look at all aspects of your spray program to see where you are vulnerable to causing drift damage. A lot has been written about ways to reduce off-target drift. Nozzle technology has been constantly improving to deliver sprays with significantly less drift potential. Don't assume however, that drift reducing nozzles eliminate drift completely. The statement that the potential for drift exists every time you turn on the sprayer still holds.

Figure 2: Rows of grapes beside a road

| Top of Page |