A farmer called me early last June concerned about the patchy growth of his canola plants in one of his fields. Upon returning from a 10-day trip, Steve, who farms 2,000 acres in the Spirit River, Alta. area, noticed his canola plants weren’t looking as good as they should have been. He said some of his plants were shrivelled and dying, some had holes in the leaves and stems, and others were just gone. “I think flea beetles have chewed holes in my plants,” he said, “and maybe some chemical residue is causing them to die.” Steve told me the plants had been emerging evenly, and he hadn’t noticed any damage before he left on his trip.
First thing the next morning, I headed out to Steve’s field. In general, the whole area was patchy — the hilltops had bare spots, some strips of the field were less populated than others, seedlings had holes and evidence of chewing on their stems and leaves, and some plants were wilted and brown in colour. Of most concern to Steve was the severe damage to the plants on the west side of the field. Most of these plants had holes in their leaves, or they were missing altogether. Steve did not want whatever was causing this damage spreading to the rest of his field.
Factors I had to take into consideration when deciding what could be causing the damage to Steve’s canola field were: environmental stress — low temperatures were recorded in the area (-5 C) for the past few nights and a heavy snowfall had occurred right after the crop was seeded; the soil quality in Steve’s field was poorer than surrounding fields and didn’t have much organic matter in it; the presence of chemical residue in the soil; and flea beetles may have been eating the plants. The crop had been seeded on canola stubble, and the previous crop’s swaths had been left in the field for quite some time.
Steve had sprayed the field with the first pass of glyphosate six days after seeding. What puzzled me most was Steve’s comment that the field had germinated normally and now was “turning” patchy. Upon further investigation, I discovered Steve had only checked the field once after seeding; the field was out of the way and he didn’t drive by it as often as the others. There was a chance, I thought, the field did not have good emergence to begin with. I felt confident the symptoms of the unhealthy plants in Steve’s field were caused not by one, but a number of issues.
What combination of factors is causing the damage to Steve’s canola plants? Send your diagnosis toGrainews,Box 9800, Winnipeg, MB, R3C 3K7; email [email protected] or fax 204- 944-5416 c/o Crop Advisor’s Casebook. Best suggestions will be pooled and one winner will be drawn for a chance to win aGrainewscap and a one-year subscription to the magazine. The best answer, along with the reasoning which solved the mystery, will appear in the next Crop Advisor’s Solution File.