Steve, a producer who farms 2,000 acres of wheat and canola near Spirit River, Alta., had some real trouble in one of his canola fields. After hearing the symptoms, I felt confident we weren’t dealing with just one issue, but a number of different factors causing the damage. Early last June, Steve called me after returning from a 10-day trip. He told me the canola plants in one of his fields had holes in the leaves and stems, and others were shrivelled and dying.
When I arrived at Steve’s field the next morning, I noticed the whole area was patchy. The hilltops had bare spots, some strips in the field were sparsely populated, there were seedlings with holes and evidence of chewing on the stems and leaves, and some plants were wilted and brown in colour. Also, the west side of the field showed significantly more damage than the rest of it — most of the leaves on these plants had holes, some plants were missing altogether, and this area, particularly near the fence line, had the sparsest population of the entire field.
The present canola crop had been seeded on canola stubble, and the previous crop’s swaths had been left in the field for some time. Also, Steve had sprayed the field with the first pass of glyphosate six days after seeding.
Steve had assumed his plants were emerging evenly in this field, but because it was located farther from the farmyard than the rest, Steve checked it only once after seeding. There was a chance the plants did not emerge well to begin with.
In order to determine the factors behind the damage to Steve’s field, I had several issues to consider. Temperatures had dropped to -5 degrees C for a few nights prior to my visit. This would explain the wilted and brown seedlings. Also, a heavy snowfall occurred right after the crop was seeded. That, in combination with soil of poorer quality and low organic matter, resulted in crusting or baking of the soil. Also, the canola plants had been seeded on canola stubble, so disease was probably playing a role as well. When I dug into the soil on the hilltops and headlands where the plant population was thin, I found
DISEASE, CRUSTING AND INSECTS ALL CONTRIBUTED TO THIS POOR CANOLA STAND
seedlings that had germinated but had damped-off, and others that had bent and turned around before they emerged. The ground was very hard in these areas. Thus, the patchiness of Steve’s field was caused by damping-off disease and the crusting and baking of the hard, poor quality soil.
The sparsely populated strips we observed running the lengths of the field were the exact distance of Steve’s swaths. Because the previous crop’s swaths had been left out in the field too long, the germination rate of the new crop decreased under the zero-till operation. Also, these conditions resulted in a lower plant population due to packing and the emergence of volunteer canola.
Flea beetles also played a part in damaging this field by eating the leaves and stems of the canola plants. Although Steve thought chemical residue within the soil could also be causing damage, I found no evidence to support this theory, such as deformity or discolouration.
I examined the worst-hit area of the field, the west side near the fence line, in the late afternoon. I had noticed evidence of insects on the plants earlier that morning — chewing marks on the leaves and stems, some plants were chewed off at the soil level. In the warm temperatures I discovered red turnip beetles feeding on the remaining canola plants. The fence line bordering the field made an ideal overwintering spot for them. The feeding damage was at its worst immediately beside the grass fence line, lessening as you moved farther into the field. Steve immediately sprayed an insecticide two sprayer widths into the field to control the beetles.
I encouraged Steve to check all of his fields on a regular basis. Many different factors can affect your crop, but, in most cases, can also be controlled if caught early. Steve is going to introduce more organic matter into his soil to improve its quality and reduce the risk of crusting issues. He will also avoid a back-to-back canola rotation in future. Despite all of these issues, because Steve addressed the problems in his field in time, he still ended up with a good yield.