Pesticides are used to control specific pests within specific areas. Pesticide applicators and farmers must carefully manage the use of these chemical tools to achieve accurate application.
Here are some of the things to be considered when spraying:
A buffer zone is the downwind distance separating the point of direct pesticide application from the nearest boundary of a sensitive habitat. Farmers must plan to leave a suitable buffer zone between the treatment area and adjacent sensitive areas.
The Pest Management Regulatory Agency (PMRA) of Health Canada has developed a web site with a calculator that helps farmers calculate the size of the downwind buffer zone required during application of some pest control products onto crops or crop land. The Site-Specific Buffer Zone Calculator calculates the required buffer zone based on weather conditions and spray equipment used for an individual spray application.
Use this calculator to reduce the potential for spray drift and the required buffer zone.
As part of sustainable agricultural practices, pesticides need to be used appropriately as part of a larger stewardship program. Farmers are stewards of the land and take steps to minimize the environmental impact of pesticides on soil, water and wildlife. One of these steps is the use of conservation buffers.
Conservation buffers help to maintain soil, water, and air quality by trapping sediment, filtering pesticide and nutrient pollution, as well as minimizing off-target pesticide movement caused by drift, water runoff, and soil erosion.
Syngenta is involved in numerous water quality stewardship initiatives and partners with growers, grower organizations, government agencies, researchers, and non-government organizations. These initiative help to preserve water quality and enhance biodiversity by promoting native habitats in agricultural areas.
These initiative help to preserve water quality and enhance biodiversity by promoting native habitats in agricultural areas.
Spray drift occurs during pesticide applications, when droplets move through the air from a target site to a non-target site. This can expose people, wildlife, and other plants to pesticide residues. However, in order to minimize spray drift, we must first understand what causes it.
The spraying equipment used in the field can have a large impact on spray drift. During applications, pesticide droplets flow through hydraulic nozzles. Each nozzle is classified according to its spray quality, which produces different sized droplets.
Smaller droplets provide better coverage, but tend to evaporate and drift onto non-target areas. Larger, coarse droplets are not easily moved by the wind but are more likely to run off the target area and provide less coverage.
Weather conditions, natural and man-made physical barriers, and the type of target site are additional factors that will influence spray drift.
Research has shown that for most applications, some spray drift is expected. This is not unacceptable, as very small amounts of most pesticides will generally not affect non-target sites. However, great precautions should be taken to minimize drift where highly sensitive sites occupied by humans, non-target crops, and wildlife habitats are known to be close by.
Weather and Inversions
Under normal, sunny daytime conditions, the atmosphere is considered “unstable”, which means that the air close to the ground is warmer than the air above. In these unstable conditions, increased wind speed causes different air layers to mix together. Any pesticide in the air is quickly dispersed and diluted with clean air.
At night, a “stable” atmosphere occurs, where the air close to the ground is now cooler than the air above it. This is called a temperature inversion. Instead of air layers mixing together, the cold air near the ground is slower, more concentrated, and moves horizontally, rather than upward.
Low wind speeds mean that any pesticides remaining in the air can hang over the treated area in a concentrated cloud for a period of time. If the wind speed increases, that concentrated cloud could drift over another area and cause damage.
Heavy cloud cover and some wind can produce neutral atmospheric stability conditions. A combination of no inversion, good dispersion, and consistent wind direction tends to result in the best spraying conditions.
Application Equipment and Technique
Pesticide applicators must consider several factors when treating a crop, such as swath displacement, sprayer and nozzle type, equipment calibration, application speed, and protective shields.
During normal application of pesticides, some displacement of each swath may carry pesticide to the adjacent area. Applicators usually allow for this when determining their spray run positions; for example, they may not spray to the edge of the outermost rows by adjusting those swaths. Swath displacement is a normal practice, particularly in aerial application, and can be an effective drift mitigation technique. In orchard spraying, some rows of trees may be skipped when spraying, using a similar type of swath adjustment.
Newer equipment such as tower sprayers, wrap-around sprayers, tunnel sprayers, and hooded sprayers can reduce drift, as can nozzle technology.
Low pressure or low-drift nozzles produce a medium to coarse droplet size spectrum and minimize fine droplets. Products requiring finer droplets are generally applied at a lower speed to improve coverage and reduce drift.
Shields, such as those that cover spray nozzles, allow spraying with ground equipment in higher winds.