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Herbicide drift and self-inflicted crop damage

Herbicides can damage crops in many ways. Learn to prevent loss and deal with damages

Herbicide drift and self-inflicted crop damage

Every year across the Canadian Prairies there will be many cases of herbicide damage to non-target crops. Some of this will be due to unsuitable weather conditions such as windy weather, wind gusts or inversions. Other causes are municipal roadside weed control leading to spray drift into cropland, on farm herbicide mix-ups, incorrect herbicides such as using ester forms of MCPA instead of amines or sprayer tank residues. Other causes are improper clean out of sprayer tanks, using the wrong herbicide for the crop, aerial spray drift and, very rarely, a manufacturing mix-up such as an herbicide contamination of a fungicide.

Weather inversions

Perhaps the most insidious form of crop damage is from weather inversions. It was a warm day yesterday, a clear sky overnight with lots of dew on the headlands and weeds and little or no wind at 5 a.m. Ideal spraying conditions for getting weeds out of the cereal crops in late May or early June. Not so. Beware!

This may well be an inversion where the surface air is very cool and all of yesterday’s warm air has moved upwards and they are not mixing. The only way to demonstrate this is to start a small straw fire. If the smoke from this fire moves slowly and horizontally a few feet from the ground you have got a classic inversion. If you spray under these conditions much of the herbicide’s fine droplets will stay airborne and move for hundreds of yards to miles. Damage is caused when a cereal herbicide drifts over a canola field or vice versa. If the spray drift damages one of your crops you grin and bear it. If it’s a neighbour, negotiations are in order. I have seen suburban gardens with grapes and shrubs damaged by herbicides sprayed over a mile away.

The correct herbicide

Its recommended that you use MCPA for weed control in your peas. Be sure to use the amine version. If you use MCPA ester and its warm humid weather you could severely damage your pea crop. MCPA ester is much ‘hotter” than the amine.

Fix in your mind your herbicide-tolerant crops. Is it for InVigor canola or glyphosate-tolerant canola? I have seen mistakes. I have even seen MCPA and even 2,4-D sprayed on canola crops in past years.

Roadside drift

Many Prairie jurisdictions, particularly in Alberta use picloram for roadside weed control. If you are growing very sensitive crops such as potatoes, peas or faba beans be sure to inform your county weed control specialists that they are not to spray particular roadsides that have fields with these crops. They will supply you with “do not spray between the signs” boards. If you do not you can lose acres of these crops from spray drift as well as persistent damage on potatoes, particularly seed potatoes.

Sprayer tank carry over or clean out failure

“The small amount left in the tank that I used on the cereals is not gong to hurt the canola.” How small was the amount and how much canola yield did you lose?

Some herbicides require much tank cleaning with chemicals, as indicated on the herbicide label instructions. Follow the label for the tank clean out procedure or lose hundreds of bushels of canola because, for example, you neglected to do the proper job following your cereal crop spraying efforts.

Windy weather

Better to skip a windy or blustery day since. If you spray, the wind will greatly reduce the herbicide efficacy, as well as damage shelterbelt trees and adjoining non-target surrounding crops. Windy weather causing spray drift, especially aerial application or inversion conditions can result in suburban gardens or acreages initiating herbicide damage lawsuits. Such lawsuits keep you awake at night.

Unexpected damage

In a few rare cases the manufacture is to blame for herbicide injury. Back in 1990 I was asked to look at a few thousand acres of canola that had been aerially sprayed with fungicide. The canola crops at full bloom were significantly injured. The flower heads were twisted and distorted. When I questioned the owner and the aerial applicator, I found that the fungicide in question — registered for use on canola for sclerotinia control — had been purchased south of the border, technically illegally. I was at a loss as to the cause of damage until I contacted colleagues in the U.S. I was informed that major quantities of a registered fungicide had been contaminated at the manufacturing plant by up to 10 per cent with a sulfonylurea herbicide. Lots of lawsuits ensued in the U.S. leading to the withdrawal of that specific fungicide.

Spray drift froma neighbour causing damage

A friendly neighbour:

Before considering litigation, arrange for a social meeting with your neighbour, ideally with a neutral third party in attendance. Describe the type of damage caused to your crop and if possible, arrange for a visual look at the crop, again in the presence of a neutral third party. If you and your neighbour are on good social terms, come to an agreement where your neighbour agrees to compensate you for your best estimate of crop loss at the end of the harvest season. No need for expensive lawsuits or lawyers and both parties can remain good friends.

An unfriendly neighbour:

Now you have got to think clearly, especially if the neighbour has repeatedly caused you significant crop loss by accident or just plain repeated and careless herbicide application over the past few years.

If the cost of the crop damage from herbicide drift is less than $50,000 (at least in Alberta) you can use the small claims court.

In order to claim for damages, if no agreement is reached with your neighbour in the presence of a neutral third party, you will need lots of incriminating data.

  1. The day that you noticed the damage.
  2. The day (approximate) that the neighbour sprayed the cropland.
  3. Was it the neighbour or a commercial applicator?
  4. The weather conditions on the day the neighbour’s crop was sprayed (windy, calm, hot?).
  5. Lots of photographs. Include one or more witnesses showing the damaged plants in your photos.
  6. An estimate by you and one or more neutral individuals on the probable crop loss.
  7. Lots of photographs showing the progression of the damaged crop every few weeks until harvest, along with witnesses in the photos.

If your losses are under $50.000 file a small claim at your local jurisdiction in Alberta. In Saskatchewan small claims limits are $30,000; Manitoba $10,000 with $2,000 costs; B.C. $35,000 and in Ontario minor amounts and judgements are complex. If your claim exceeds your provincial limit, you can still claim the maximum amount and forget the overage.

If you think you need a lawyer, ask what fees they will charge and, after consultation, your chances of winning the damage claim. If your claim succeeds you could also be awarded the cost of the litigation, or if you lose you might end up paying the fees.

Lawsuits can drag on for years and cause lots of frustration so it is always the best policy to come to an amicable agreement with your transgressing neighbour. You do not lose sleep and you could end up as good friends.

Winter injury in North America

You heard it here first.

Dr. Ieuan Evans believes that the record cold spell in Eastern and Central Canada and the United States may have caused considerable crop damage.

If there was poor snow cover in some areas, particularly coupled with dry soil conditions, then winter wheat, winter canola, alfalfa and perennial forage crops could be significantly damaged. The unusual cold could also do lots of damage to Canadian and U.S. fruit crops. Very low temperatures kill grape vines and flower buds in apricots, sweet cherries, peaches, apples, pears, and nectarines, as well as raspberry canes and strawberry plants.

Widespread losses could well mean higher fruit prices. Such cold temperatures may also have caused twig or wood damage which could take fruit trees years to recover.

About the author


Dr. Ieuan Evans is a forensic plant pathologist based in Edmonton, Alta. He can be reached at [email protected]



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