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Bill thought there was something wrong with the in-crop herbicide he’d sprayed on his canola field in early June. A week after spraying his canola, the Alberta farmer noticed that his plants looked sick, and some were even dying.

Soon after Bill phoned me, I visited his 2,200-acre farm where he produces canola, barley and wheat near Waskatenau. One area of the canola field in particular looked damaged — the plants were significantly shorter than other surrounding healthy plants, and their leaves were cupped, purplish and covered with white speckles. The older leaves on the damaged plants had turned brown, however, the plants were projecting new growing points.

Growing conditions had been excellent so far that season, so I had no concerns of environmental factors playing a role in the damage. The seed lot was fine, as were Bill’s fertilizer application rates. However, the distinct appearance of the damaged field — the stunted and dying plants were mostly concentrated at one end of the field, the entry point, with the damage gradually tapering off toward the farther end of the field — led me to believe we were dealing with a sprayer or herbicide issue.

We examined Bill’s sprayer, checking for any mechanical issues, but found none. However, the sprayer boom length was the exact same width as the damaged area! We were dealing with a chemical injury, but applied correctly, the in-crop herbicide Bill had sprayed mid-June could not have caused this type of damage.

When we checked Bill’s herbicide application rates, we found they were correct. Had they been incorrect, the whole field would have been adversely affected. Bill said the sprayer and tank were new and the herbicide he’d sprayed on his canola was the first chemical to be put in the tank.

“Did you happen to spray a pre-seed burn-off with your new equipment?” I asked.

Suddenly Bill’s face lit up. “Yes, I guess I did. That’s got to be it!” he said.

We discussed the steps Bill had taken to clean and rinse his tank between chemicals. Bill’s clean-out practices were not adequate to thoroughly remove all traces of chemicals between applications.

The canola plants were suffering from a Group 2 herbicide injury due to chemical residues left in the tank, filters and boom.

Effective sprayer clean-out procedures include pulling off and cleaning filters during the first rinse, and adding a solvent cleaner to the second and third rinses of the equipment. This removes residue off the tank wall, hoses and screens.

When cleaning a sprayer, do not skip any steps and triple rinse every time between chemical applications. Even in a stainless steel tank like Bill’s, chemicals can adhere to tank walls and filters.

This crop advisor casebook has a bittersweet ending. Bill was relieved to have some answers about his ailing canola plants, but the injury caused a crop loss of 70 out of 160 acres. However, conscious of best clean-out practices, Bill is well-equipped to take on tank residues in the future. †

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