Canola stands of 1 plant per square foot usually have 50-75% of the yield potential of an optimal stand density (greater than 6 plants per square foot) at the same stage of maturity. But there is usually a yield advantage of earlier seeded crops. Therefore, a thin stand can have 90% of the yield potential of a thicker stand seeded 2 weeks later. By the end of May, established thin stands usually will outyield canola reseeded at that time and will save the extra costs due to reseeding! Murray Hartman, oilseed specialist with Alberta Agriculture and Rural Development, says growers tempted to reseed fields with thin stands should think twice.
MCPA and 2-4,D are not registered for use ahead of canola. The residual can be deadly to emerging canola plants. Growers with big canola volunteers to control ahead of the crop may have heard that MCPA is safer than 2,4-D and that MCPA Ester is safer than Amine, but none is registered — or recommended.
Early-seeded crops are being spraying for flea beetle damage. The action threshold for spraying is when 25% of the leaf area is damage or missing. Economic threshold is considered to be 50% of leaf area missing or damaged. When damage covers 25% of leaf surface area, on average, and if flea beetles are still actively feeding, arrange to spray the affected field. Flea beetles slow down in cool, wet weather, but may take refuge on stems and the undersides of leaves. Watch for stem feeding.
After a damaging frost, give canola crops 3 to 4 days to recover prior to assessing damage. If it remains cool recovery maybe longer. If after 4 days, you don’t see signs of new green growth on at least 1 plant per square foot, then reseeding may be the best option. (The same goes for wind damage, which was reported in part of Manitoba last week. Some seed may still be emerging and if growing points of damaged plants remain intact, recovery is possible, but plants cut off below the growing point will likely die.) After a frost, also remember to wait 2 or 3 days before spraying herbicide. Giving time for canola and weeds to recover reduces stress on the canola and improves herbicide efficacy. If frost has been heavy and there is significant leaf damage, foliar (post-emergent) herbicide applications will not successfully control the damaged weed until they have recovered and grown new leaves.
Something to think about for next spring: About 10,000 acres of canola in the Peace region are being reseeded due to early season stressors such as flea beetle pressure and damping off, which may be a result of deep seeding into cool soils. Most of those acres were seeded April 20-25 and emergence was delayed and patchy. By the time the crop emerged, seed treatment protection had tapered off.
Crop insurance cut off dates for full coverage are June 1 in Alberta, June 20 in Saskatchewan and June 10 for northern Manitoba and June 15 for southern Manitoba. Click your province for a link to crop insurance details: Alberta Saskatchewan Manitoba
Growers who are seeding canola on fields originally planned for cereals need to consider their herbicide use last fall and this spring. Did they use products with residual activity that are not registered for use ahead of canola?
Adult diamondback moths have already been found in pheromone-baited traps in several areas of Manitoba and Alberta. This does indicate an early arrival of the moths. Scott Meers, insect management specialist with Alberta Agriculture, says the early arrival means we’ll probably have issues as the season progresses. Be prepared to watch closely later in the season when the next generation of larvae emerge and start feeding.