Authored by: Tracey Baute, Meghan Moran, OMAFRA and Dr. Rebecca Hallett, University of Guelph
Swede midge populations are high this year while the canola crop is still quite young. Despite trap captures already reaching the accumulated trap threshold of 20 midges total, there are a few things to consider before deciding to spraying this early:
- Trap threshold – The recommendation that the first spray be made after a total of 20 midges accumulated across all traps in a field was set based on historical field data, looking at which fields experienced damage and which ones did not. Fields that had midge trap counts accumulating in the 100s of midges up to the 5-leaf stage had much more injury than those fields that had traps only accumulating 20 or 30 or even 50 midges per day. So the threshold for applying the first spray was set conservatively at a total capture of 20 midges with counts beginning at the first leaf stage. After you have made your first spray, you should move to the action threshold of 5 midges/trap/day with approximately 7 days between insecticide applications.
- Crop stage – More plant injury is experienced when there are buds starting to form on the plants. So it is likely more important to protect the plants in the 5- or 6-leaf stage or later when there are tiny buds starting to form. That said, if the field is accumulating 100s of midges per trap per day in early vegetative stages (3-4-leaf stage), then an application may be warranted. At early growth stages a border spray may be sufficient, since swede midge populations are higher along the field boundaries.
- Other pests – If the field in question also has flea beetle populations no longer being knocked down by seed treatment, then there is more reason to apply the insecticide early. If there is flea beetle present, then Matador is the recommended product so that both flea beetles and midge are controlled.
- Product Requirements – If you do spray, keep in mind that both Matador and Coragen can each only be applied 3 times per season. There may be additional applications required for midge or other pests so consider the economics of spraying this early. Rotating between these two products is recommended to reduce the risk of resistance. Note that Coragen cannot be applied to fields within 60 days of planting if Lumiderm or Fortenza seed treatment was used. So spraying Matador early may hinder your ability to rotate to Coragen for the next application if it is still within 60 days of planting.
- Second application timing – It is most critical to protect the early buds. If only one application can be afforded, stick to applying a product between the 5-leaf stage and bud initiation if trap thresholds are reached. If you apply a product when the crop is in the 2-3-leaf stage, then a second application may still be required a week later (if traps reach the threshold of 5 adults/trap/day) to protect the later vegetative stages when bud initiation is occurring. Label restrictions state that Coragen can be applied once every 5 days, Matador can be applied once every 7 days.
For more information on swede midge and management, refer to the swede midge infosheet at: