Last June, Mike, an excellent farmer who farms 7,000 acres of wheat, canola, barley, peas and flax in southeastern Saskatchewan, called me about his sparsely populated, unhealthy and dying stands of canola. He thought the particular herbicide-tolerant variety he planted that spring had no vigour; all of his other canola fields were doing well. He asked me to come out and have a look for myself at this ill-performing variety.
I’d expected some calls like this one — there had been plenty of environmental stress on all crop types already this season. No one was going to forget the growing conditions of 2010 for a while. But when I arrived at the field, I had my doubts that environmental stress was the only factor affecting Mike’s canola field. The first thing I noticed were lines, in some places the full length of the field, dividing the area into definite strips. In some of those strips the canola plants were sickly, showing various stages of maturity and some were dying. I was curious to discover the cause of those lines, especially because Mike was an experienced farmer.
Mike thought there may be a problem with the variety, but no other farmers had reported concerns with that particular variety or seed lot. Stress due to excess precipitation could damage the canola plants but it wouldn’t explain the presence of the precise pattern of lines in Mike’s field. Also, Mike’s fertilizer application rates were all correct and consistent with his other canola fields, his machinery was working well and the settings were correct during seeding.
The lines in his field suggested a spray pattern, but they could not be caused by fertilizer application. Mike had used the recommended Group 10 herbicide on this field, and the pattern in the field was consistent with the way Mike had sprayed. As soon as I heard he’d used a Group 10 herbicide I knew what the problem was. I’d come across this problem a few times in the past.
Because this herbicide can work like a detergent, drawing previous chemical residues out of the sprayer system, farmers must be very careful about what product was in the tank prior to spraying, and must be diligent when cleaning the tank. There are definitely some chemicals that leave deadlier residues in the tank, and some that are far harder to clean out of the tank than others.
In Mike’s field, the damage was more noticeable in the areas where the sprayer booms were first activated, after turning on the headlands, thus it was evident that the unwanted chemical from the boom ends had mixed with the herbicide when the booms were shut off.
The importance of thoroughly cleaning out the tank and sprayer before spraying a different crop or products cannot be overstated. Some cleaning products are better than others and can actually neutralize some chemical residues. Removing the caps from the boom ends to flush the booms completely is also a good management practice.
Unfortunately for Mike, the environmental stress the crop was under this year enhanced the damage to that field more than it might have in other years. But the plants in that field ended up coming back well. In the end, there was not a noticeable difference in yield, even with the heavy precipitation. Mike was lucky — if it had been hot and dry the damage may have been far worse.