| | Assess hazards prior to application | Buffer zones | Rights and responsibilities
This information is intended for producers that are hiring custom pesticide applicators or performing their own pesticide applications
Pesticides (herbicides, insecticides, fungicides) can leave a target application site in two forms: vapour (gas phase) and droplets (liquid phase). Vapour is specific to each pesticide and accounts for the odour detectable at application sites. Spray droplets can move to off-target sites with wind or as the result of a temperature inversion or over- spraying into non-target areas.
The drift management techniques covered in this sheet apply primarily to droplets rather than vapour. However, basic drift management principles apply to both.
Assess Hazards Prior to Application
The area surrounding an application site usually has a number of land uses that will have different tolerances to pesticide deposition. Drift management requires the accurate assessment of off-site tolerances prior to application.
It is important to manage spray droplets to a high level of precision considering the sensitivity of adjacent areas. For example, some adjacent field crops can be affected by very low levels of certain herbicides where other crops might be relatively tolerant. Aquatic life tends to be affected by much lower levels of pesticides than crop vegetation. Farmsteads and other residences may be a particular concern where products are of higher toxicity to humans, especially someone who has respiratory problems. It is extremely important to be aware of surrounding conditions PRIOR to treatment while you still have time to do something about it.
Fortunately, information and technology are available to manage drift concerns and ensure that pesticide lands on the target crop where it will have some benefit.
Buffer Zones
A “buffer zone” is the distance left between the last swath of an application and the edge of an adjacent protected area.
A buffer zone is intended to capture the major portion of driftable droplets within a treatment area to minimize risk to adjacent protected areas. The size of a buffer zone depends on the amount of driftable droplets generated by an application and the distance that these droplets will travel. Consult the product label or provincial crop protection guides for specific recommendations.
The buffer zone size can be adjusted by compensating for the three key factors that affect droplet drift: droplet size, wind, and boom height.
Droplet Size. All spray application equipment will produce some small droplets that are able to drift. Spray nozzles that deliver a larger droplet size generally produce a lower proportion of small droplets. Some nozzle types are designed to produce more uniform droplets with less production of smaller droplets. The larger the droplet size, the smaller the buffer zone requirement. Applying pesticides with the water volumes recommended on product labels ensures product performance. Using reduced water volumes and compensating by using a smaller droplet size can present a drift hazard with less reliable product performance.
Wind. In general, pesticide applications using boom application equipment (ground or air) should be terminated when wind speeds are above 16 - 20 kph. Some labels will specify lower wind speed limits. Where the buffer required to protect an adjacent area is excessive at a particular wind speed, wait until winds are blowing away from the sensitive area or until winds have died down. Spraying when winds are blowing away from a protected area can offer additional protection -droplets do not drift upwind.
Boom Height. The height of nozzles above the ground determines how much time droplets are exposed to air currents and to forces that will reduce droplet size. By lowering boom height, droplet drift can be reduced without further increasing droplet size or buffer distance.
Other Factors. Higher temperatures (above 25 degrees C) and lower relative humidities can increase the risk of pesticide drift because of their effect on reducing droplet size through increased evaporation. Larger droplets will be less affected by temperature and humidity changes.
Beware of “dead calm” application conditions
Pesticide applications should not be made when a temperature inversion is present. Temperature inversions occur during very calm conditions (usually in early morning or late evening) where very little air mixing occurs. As a result droplets can “hang” in the air as a concentrated cloud for some time after application and, when winds pick-up, this cloud can move to where it may present a threat to adjacent areas. Smoke can show the presence of an inversion. When smoke moves across the sky in a cloud rather than moving upwards and dispersing, an inversion is present.
Rights and Responsibilities
Producers have the legal right to apply pesticides on their property provided that the pesticide application does not contravene any by-laws, regulations, or generally accepted practices. Producers have the legal responsibility to ensure that any pesticide application performed on their property does not cause harm to adjacent properties or people. When using custom applicators, ensuring that applications are conducted by a qualified service that is legally registered to perform pesticide application is the first step in meeting producer responsibility. The second step is ensuring that the applicator is aware of potential hazards in advance of an application. Producers may be held accountable for compensation to adjacent landowners if pesticide damage occurs.
This information has been developed and supported by:
The article Pesticide Notification may also be of assistance.
For more information, contact Jock McIntosh |
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