By Nicole Philp, Canola Council of Canada
Flea beetles, dry soils, wind and other factors can influence seed and seedling survival.
Unless scouting and counts are done repeatedly through the first few weeks after seeding, these influences may be missed and the seeding tool or other seedbed conditions may be unfairly blamed.
Start with plant counts. As a guide line, count the week after seeding, then a few days after what you think will be peak emergence, and again at the 4-5 leaf stage. For tips on counting, search for the article “Count plants” at canolawatch.org.
Use the seeding rate calculator’s “plant survival” option at canolacalculator.ca to see how plant stand relates to seeding rate.
If seed survival is less than expected or hoped, look around for clues that may explain why. Look for:
Seeder performance issues. Rows with poor emergence beside rows with good emergence would suggest a drill problem — maybe due to varying opener depth or plugged lines.
Insect damage. Flea beetles are usually the most serious insect pest this time of year. Examine newer leaves for recent damage and look for stem feeding.
Note that canola seed treatments require a bit of feeding to stop flea beetles, so older leaves may show some damage for this reason while newer leaves may be undamaged – indicating the crop is growing ahead of the feeding and a foliar insecticide application is not likely needed.
Look for cutworm as well. Search for scouting tips at canolawatch.org
Disease symptoms. For example, blackleg can infect young canola plants when temperatures are warm and soil is moist. The earlier the infection, the higher the yield loss from blackleg. Scout cotyledons looking for greyish-white lesions speckled with black pycnidia. Severe infections will cause girdling of the stem and premature death of the plant.
Weeds. Early-season weed competition is the most costly to yield. If fields did not get a pre-seed burnoff, expect to see some weed competition and spray them early in the window. Earliest spray opportunity varies by HT system.
Herbicide damage. Carryover of residual products from last year can be a concern in dry conditions. Mistakes with pre-seed burnoff products can also cause damage.
Fertilizer damage. This can be difficult to diagnose but higher rates of seed-placed fertilizer in dry soils and with low seed-bed utilization (narrow openers and wide rows, for example) can cause seed and seedling mortality. Seeds that are dried up and powder-like inside may be fertilizer damaged.
Frost. Any amount of frost can start taking out plants. One factor is the daily highs leading up to the frost. If days had been cool (10°C), canola plants may be more acclimatized to a heavier frost. If days had been warm (20°C), even a light frost can cause some seedling death.
Wind. High winds can blow seeds and seedlings right out of the ground, especially if topsoil is dry. Soil-particles blown by the wind can also “sand blast” seedlings.
Residue. Thick or uneven residue can have implications for frost damage and consistent seed placement into soil. Seedlings growing up through residue tend to have longer more exposed hypocotyls.
For links to get more information on all these scouting topics, search for the article “Start scouting the week after seeding” at canolawatch.org. While there, sign up to receive our Canola Watch agronomy email through the growing season.