Spraying with Greenhouses Nearby

Greenhouse expansion has seen large ranges built in locations where no one would have imagined 20 years ago. For some farmers, this means that as they work their fields they can see the classic ridge and furrow profile of a large greenhouse range. Greenhouses are essentially protected environments where a wide range of crops can be grown under carefully controlled conditions. Temperature, relative humidity, carbon dioxide levels, light levels, irrigation water and crop nutrients are all managed to have the crop grow and develop. The crop growing in the greenhouse is at the mercy of the plant manager to provide each and every plant need.

Managing temperatures within a greenhouse is accomplished by ventilating. Ventilation exhausts warm greenhouse air and draws in cool outside air. This poses the biggest risk for bringing in spray droplets that are suspended in the outside air.

Spray Drift - The Law

The Ontario Pesticides Act is perfectly clear on the expectation of a sprayer operator as it pertains to spray drift. In plain language it says 'Thou shalt not drift'. This means that every time you spray, drift should not be allowed to occur no matter what is adjacent. Therefore it doesn't matter whether you are spraying next door to a greenhouse, beside a field crop or adjacent to a processing crop -you need to do everything possible to avoid drift every time you spray a field.

Figure 1- Be aware of possible drift concerns such as greenhouses.

What Can Be Done

Numerous options exist to minimize or reduce the potential for spray drift and they are listed below. Producers may use one or more of these drift reduction options to minimize spray drift.

1. Use higher water volumes

2. Use drift reducing nozzle technology

3. Do not spray in winds that would allow drift to trespass

4. Do not spray in completely calm conditions

5. Use a drift retardant

6. Minimize nozzle-to-target distance

7. Read product labels thoroughly and understand the cautionary spray statements

8. Wind screens and nozzle shrouds reduce spray drift

9. Maintain open communication with your neighbour

Communication is the Key to prevent Problems

In doing background work for this article, a number of the vested interest parties stated that communication was absolutely critical to avoid major drift problems. Communication can be both good and bad depending on your perspective.

As a greenhouse operator, knowing the spraying intentions of adjacent farmers would allow you to prepare. Knowing what, when and where spraying was to occur allows the greenhouse manager to close wall and/or roof vents for a time to prevent airborne spray droplets from entering the structure. On a bright sunny day, expecting a greenhouse to be closed completely for hours will just not work. Venting is the only quick way to cool a greenhouse. On a sunny day any greenhouse will heat up quickly. Excess heat build-up will cause undue plant stress and possible crop damage and lost production.

As a sprayer operator, you may not want the neighbour to know what you are planning to spray. The reason that's usually given is "If I tell them I'm spraying a certain product they will look for injury symptoms of that product". Under the Ontario Pesticides Act, drift should not be allowed to occur. Doing a good job of spraying should not result in any spray drift. Be careful about sneaking in and spraying, hoping nobody notices. There may be serious consequences if some of the spray droplets you let off into the environment get drawn into the greenhouse with the ventilation air. You will be liable if you allowed spray drift to go off-target and cause crop damage. Check with your insurance company to see that you are covered for such unforeseen circumstances.

Figure 2- A greenhouse may be as close as just across the road. Be careful since
drift into an enclosed environment such as a greenhouse could cause substantial problems.

Keeping Spray Records

Spray records should be part of your regular spraying routine. These records document the who, what, where, when, why and how the job was done. These records are good management practice that may also be very important if your spraying prowess is called into question, such as a spray drift or crop damage complaint at some point in time. Keeping detailed records may seem a nuisance if you don't have to use them. Remember, it's always better to record more information than have insufficient information when you need it.

What Needs to Change

Everything possible should be done to avoid off-target movement of pesticides. Spray drift is bad for good neighbour relations but also indicates that all the material applied did not get to the site of action. Consider spraying when air movement is away from greenhouses or other sensitive crops to significantly reduce the chance for causing crop damage.

For more information call the OMAF CropLine Hotline toll free number at 1-888-449-0937.

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