Improving Spray Application And Reducing Spray Drift With Farm Windbreaks

Getting effective coverage of insecticides and fungicides onto crops can be hampered by spring and summer winds. Excessive wind during a spray application can reduce the effectiveness of expensive spray material by disrupting the spray pattern as it leaves the spray nozzle. It takes very little wind near the sprayer to change the spray pattern, even where the sprayer is perfectly calibrated. Waiting for a 'window-of-opportunity' to apply spray between random windy days can be frustrating for growers.

In addition to affecting spray coverage on the crop, wind can also carry spray material out of the field into neighboring properties, onto buildings and onto adjacent crops as spray drift. Finding ideal calm conditions to apply herbicides can be even more frustrating than it is for insecticides and fungicides because drift of herbicides can cause damage to nearby crop plants and to neighboring vegetation.

Ideally, all crop protectant materials should be prevented from leaving the area that is intended to receive the application of spray material. Where spray material drifts offsite complaints from neighbours sometimes follow. Naturalized areas such as water courses and woodlots also need protection from drifting crop sprays. In conventional farming, narrow windbreaks or wide shelterbelts, planted around agricultural fields are known to protect sensitive crops from damaging wind and may help reduce spray drift offsite.

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Photo 1. A nicely sheltered field is a conventional farm practice.

Spring is a good time to think about windbreaks on your farm property. Do existing shelterbelts need renovating? Are there holes in existing windbreaks that can be filled with new trees? Are sensitive horticultural crops being protected enough from damaging wind? Can a new shelterbelt help improve spray application coverage and reduce spray-drift problems? Perhaps existing windbreaks require thinning of branches near the ground to prevent frost pockets from forming in sensitive crops.

On the upwind side of fields, shelterbelts are known to moderate incoming wind and can allow for more effective spray coverage. Although a good windbreak can't eliminate excessive windy conditions it can often provide farmers more time, or a wider 'window-of-opportunity' during the day or night to apply spray material. To reduce drift of airborne spray material out of the field, conifer windbreaks have the ability to catch drifting insecticide and fungicide at the downwind edge of fields.

When considering what tree species to use for a windbreak it is a good idea to plan for more than one species. Trees, like crops have specific insect pests and diseases that can affect the health of tree rows. Some tree species tolerate droughty seasons while other tree species tolerate wet seasons. Having at least 3 to 5 different conifer and deciduous tree species alternating along a windbreak can help the overall health of the windbreak, to tolerate changing seasonal weather and pest situations better than a single tree species.

Photo 2. Eastern white cedar, spruce and deciduous trees alternate along the tree row.

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Selecting trees for windbreaks

Eastern white cedar is sometimes reported as having too dense a canopy when used alone which can create wind turbulence and crop damage near the tree row. White cedar is however a sturdy tree in exposed areas but may be more useful if it is alternated with other conifers such as Norway spruce and white spruce. Spruce is not as dense as white cedar and does not create turbulence downwind of the tree row. Spruce species are very effective as windbreak trees.

In drier sandy soil red pine, white pine, Austrian pine and Colorado spruce are tolerant of dry sites and can be mixed with eastern white cedar. Near highways, sprays of winter road salt from passing vehicles can kill many tree species. Austrian pine and Colorado spruce are more tolerant to airborne sprays of winter road salt because of a thicker waxy layer that protects the trees during winter. White pine should not be planted near currants and gooseberries because these crop plants are alternate hosts of white pine blister rust disease which kills white pine trees.

In Essex county some landowners are testing eastern red cedar as a species for field crop windbreaks and may provide better results than eastern white cedar. Eastern red cedar is tolerant of dry shallow soil, conditions of low soil fertility and may also perform well around some horticultural crops. Eastern red cedar should not be planted near apples due to its' association as an alternate host of cedar apple rust disease.

Grey alder is being tested as a deciduous windbreak species and is known to fix nitrogen from the atmosphere, adding to soil fertility for other windbreak species in the tree row. Hybrid poplar is a fast growing tree in windbreaks but is short lived (10 to 15 years) due to trunk canker disease. Poplar roots compete vigourously with nearby crops for nutrients and moisture reducing crop yield for 50 or more feet from the windbreak.

Basswood trees can tolerate wet soil conditions as a windbreak species and its' late spring flowers provide a useful refuge for pollinating insects such as honey bees. Black locust is also a 'bee-friendly' tree for pollinating insects however, it is a very poisonous tree and should not be used near food crops or livestock in windbreaks. Native honey locust is a safe nitrogen-fixing tree species.

Conservation Authorities can provide additional information on species to use for farm windbreaks, on species availability and on planting design. If spray applications are hampered by wind, or where spray drift is a concern, take a close look at your farm windbreaks.

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