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Spraying for lygus bugs and cabbage seedpod weevil has begun in southern Alberta, and diamondback moth larvae are showing up in higher numbers. The critical time for diamondback moth larvae control is during pod formation.
While scouting for insects, you may find tiny thrips. (See the photos below.) Thrips, which cause twisted pods on canola, have been spotted in parts of Alberta this year. There are no established thresholds for control, but if pod damage is due to thrips and not diamondback moth larvae, for example, then a spray may not help.
Export Ready: Don’t use Ronilan on canola. Canola tolerances for vinclozolin, the active ingredient in Ronilan, are no longer in place for the U.S. This means that any canola treated with Ronilan is no longer acceptable for shipment to the U.S. Click here for the latest Export Ready factsheet.
Export Ready: Don’t use malathion on canola bins. Malathion cannot be used to treat bins where canola will be stored or to treat canola as it goes in to storage. This can result in residues in the canola. If the bin was treated previously, do not store canola in the bins within six months of treatment. Click here for the latest Export Ready factsheet.
Prepare for 2011. A large portion of unseeded and drowned out acres in 2010 will likely be seeded to canola in 2011. In preparing the unseeded fields for next year’s canola, use herbicide products that do not leave residues harmful to canola.
When you see sclerotinia symptoms — bleached white and possibly brittle areas on the stem — it’s too late to manage the disease for this year. But you can use that information to plan a more proactive sclerotinia monitoring and control plan for next year. For more on sclerotinia management, click here to hear Kelly Turkington, crop pathologist with AAFC in Lacombe, Alta., on ACPC radio.
Sclerotinia survey. MAFRI, AAFC and Canola Council staff are collecting canola flower samples at 20% and 50% bloom stages to test for sclerotinia spores. The same fields will be surveyed again for disease incidence just prior to swathing. The goal is to improve sclerotinia forecasting tools. Vikram Bisht, the provincial plant pathologist with MAFRI, says every effort will be made to contact growers prior to subsequent sampling, but the rapid advancement of the crop in eastern Manitoba has necessitated random sampling of a few fields. If growers have concerns or would prefer their fields not be sampled, contact Bisht at 204-745-0260.
What to do about strange growth and missing buds
Many canola fields in the central Peace region are exhibiting unexplained symptoms. In some cases, as shown in the first photo, the plants are green and lush but bud clusters are not forming. In other cases, as shown in the second photo, plants are spindly and purplish. The common factor seems to be fields of canola on canola stubble, but it’s not limited to any one canola herbicide system.
Until you know the cause of damage, take no action. There’s no sense spending money on fungicide, insecticide or nutrient topdress without properly identifying the target problem.
Herbicide carryover is a possible cause for the lush plants with missing buds. (See the top photo.) A soil bioassay can identify the herbicides present in the soil. Alberta Innovates in Vegreville does soil bioassays. They cost $150 per sample and the turn around time is 4-6 weeks. For more information, call or email Sandi Scott at 780-632-8217 or sandi.scott@albertainnovates.ca.
Other possibilities:
—Lygus bug feeding on drought-stressed canola may also explain the combination of lush growth and blanked out buds.
—Sulphur deficiency may explain the spindly purplish plants in the bottom photo.
—Phytoplasma carried by leafhoppers is possible, but herbicide carryover is more likely. That has to be ruled out first. Again, until the cause is known, hold off on action.
Swede midge has been mentioned as a cause, but that’s unlikely. Swede midge have not been reported anywhere west of eastern Saskatchewan.
For a presentation on what causes blanks or flower abortion, watch the ACPC webinar with Murray Hartman, Alberta provincial oilseed specialist.
For more information, download the CCC factsheet “Missing pods or blanks on the main stem: What could be the cause?”
