From Canola Council of Canada
Bald patches. Blank areas in the field can result from dry seedbeds, heavy winds, drowned plants, seed rots, cutworms and other insects, and from gophers.
Unthrifty, yellow or malformed plants. Unhealthy-looking plants can result from seedling diseases, herbicide carryover, herbicide burn, high rates of seed-placed fertilizer, fertilizer deficiency, low vigor and deep seeding, to name a few. Malformed plants can result from herbicide injury or disease, but possibly other factors.
Damaged plants. Environmental stress such as frost or hail are possible reasons. Look for insects, particularly flea beetles and cutworms, but also wireworms and early grasshoppers. Even if you don’t see obvious feeding on leaves, look under the leaves and on stems. If flea beetles have moved down the plant due to rain or wind, they can actually do more damage. Severing a stem is far worse than 25% damage on the leaf. Check leaves for blackleg lesions.
While doing the above ground scan, look at the weeds. What type, size and number do you see? This will help determine whether another spray is warranted and what tank mix and rate to use.
After the above-ground assessment, get a trowel and bucket and start digging around damaged plants. Look for cutworms and wireworms in the top 4″ of soil. Look at the roots for signs of insect feeding or disease damage. Chomped roots are usually insect damage. Mushy or thin wiry roots and stems are often the result of seedling disease.
Thin stands need extra protection
The key with a thin stand is to do what it takes to protect those plants. A stand needs a minimum of 4-5 plants per square foot to reach its yield potential. For a canola field at or below that plant population, consider lowering the action thresholds for insect, weed and disease management all season long.
It helps to keep a scouting notebook and jot down all observations. Even if you see nothing of concern, early scouting gives you a baseline for crop emergence and condition of the stand. Then you’ll know for sure something is wrong if the crop doesn’t look as healthy the next time you scout.
Problems can escalate quickly this time of year and cause irreparable damage if not addressed early. Scouting alerts you to these problems. And while the cause and solution may not always be obvious, this insight motivates you to get help and make an informed decision on the most economic course of action.
Visit www.canolawatch.org for more canola agronomy information.