Despite a generally cool spring, flea beetles are starting to emerge in some parts of the prairies. The Canola Council of Canada (CCC) is advising canola growers to check their crops regularly since flea beetle feeding can reduce yield and lead to a longer flowering period, later plant maturity, and shorter plant height.
“Early season feeding by flea beetles is characterized by pitting and shot holes on both sides of canola cotyledons, as well as pitting on the stem of the plant,” says CCC agronomist Matt Stanford. “After emergence, fields should be checked every few days for evidence of damage as canola is most vulnerable to flea beetle feeding at the cotyledon to 2-leaf stage. If flea beetles are present, check affected fields daily as problems can escalate quickly, especially if canola plants are growing slowly or are under stress.”
Due to cooler temperatures across much of the Prairies, canola emergence has been delayed in many fields. In this situation, it is critical to remember that the protection from the insecticide portion of the seed treatment starts when the seeds are first put into the soil, not when the plant emerges. In some of the earliest seeded fields, protection may be tapering off so as conditions warm, watch closely for widespread flea beetle activity.
The economic threshold for flea beetle control is when 25% or more of the cotyledons are damaged. If 25% defoliation is reached, foliar insecticide application may be needed if plants are growing slowly or are under stress, and if beetle feeding activity is increasing.
Evidence of feeding does not automatically mean spraying is warranted, reminds Stanford. “Unwarranted spraying can cause harm to beneficial insects and can also contribute to the development of insecticide resistance. With current seed treatments, flea beetles must feed on leaf material and ingest the insecticide for control so some feeding damage is normal.”
Flea beetles make their way into canola crops from the edges of fields. By catching a problem with flea beetles early, producers can often spray the perimeter of their fields and stop the infestation before it becomes widespread.
Growers are advised to be particularly careful in areas that saw high flea beetle populations around swathing time last fall as this can be used as an indicator for spring pressure. These areas include: Lethbridge, Alberta; Vauxhall, Alberta; St. Albert, Alberta; parts of southern Saskatchewan; and south central Manitoba.
For more information in your area, contact:
Derwyn Hammond, Manitoba Region, 204-729-9011
Jim Bessel, North Central and North Eastern Saskatchewan, 306-373-6771
Tiffany Gutzke, Eastern Saskatchewan, 306-231-3663
Doug Moisey, East Central Alberta and Northwestern Saskatchewan, 780-645-9205
Matthew Stanford, Southern Alberta and Southwestern Saskatchewan, 403-345-4852
John Mayko, West Central Alberta, 780-764-2593
Erin Brock, Peace Region, 780-568-3326