Now that the earlier seeded canola fields are finally starting to emerge, canola growers should be on the lookout for a number of insects and diseases.

“Identifying any pests and problems earlier allows more time to identify the best solution, and that can really pay off,” says Derwyn Hammond, senior agronomy specialist for the Canola Council of Canada (CCC).

Seedling diseases

 

According to Hammond, the cold soils this spring have resulted in very slow germination and emergence on many fields, which can increase the risk of seedling disease issues. In many western areas the cold and dry soils will favour Rhizoctonia which causes wirestem, while the cold, wet conditions in the eastern prairies may be more conducive to Fusarium or Pythium species that cause seed or seedling decay.

 

“It is important not to assume that poor emergence is the result of disease, as the broad spectrum fungicide seed treatments used to treat certified seed typically provide good protection from these pests,” says Hammond “Many factors can result in poor emergence that could be mistaken for seedling disease. These include desiccation of emerging hypocotyls in dry soil, heat damage, wind damage, excessive seed depth, or insect damage from pests like cutworms or wireworms.

 

“The tell-tale sign of disease is patchy emergence up to the four-leaf stage of the crop. Seeds or seedlings may decay prior to emergence or the seedlings may emerge and appear normal, then topple over, wilt and die when the decay reaches the soil surface, or growth will stagnate at the two- to four-leaf stages.”

Hammond emphasizes that scouting throughout emergence is critical to catching seedling diseases, because the dead plants will decay and disappear quickly, making it impossible to accurately identify the cause. Determining the exact cause of emergence issues is the first step in avoiding similar problems in the future.

The following links contain information regarding diagnostic services available in Saskatchewan and Manitoba to help confirm the cause of emergence problems:

http://www.agriculture.gov.sk.ca/Default.aspx?DN=6398d51e-280c-43f0-b211-23af1ecdb886
http://web2.gov.mb.ca/agriculture/programs/index.php?name=aaa01s14

Insects

 

CCC agronomy specialist Matt Stanford suggests early scouting to ensure that any insect pests and/or damage in canola are identified prior to exceeding economic thresholds. A number can show up at the seedling stage, but flea beetles and cutworms are most common. Flea beetles are already causing some problems this year where cool temperatures have made canola vulnerable due to slow growth and/or low plant populations, and cutworms have also caused losses in a few fields. Wireworms are another less common pest in canola that may turn up in land recently taken out of perennial forage.

“Flea beetles attack the leaves of young canola seedlings, reducing the leaf area for photosynthesis,” says Stanford. “When flea beetle feeding reaches 25% defoliation, this is considered the ‘action threshold’ for flea beetle control, if flea beetles are active and the canola is growing slower than the rate of feeding. Yields will start to decline when the ‘economic threshold’ of 50% defoliation is reached, so growers should consider chemical intervention prior to that point if the insects are still present. Watch for ‘shot-holes’ on untreated canola or wild mustard as an early sign that flea beetles have emerged.”

Growers may also discover cutworm damage - plants cut off at the soil surface with bare spots appearing mainly on light textured soils, hilltops and south facing slopes where soil temperatures are warmer. Producers are advised to dig with a trowel in the top 2 inches of soil and sift to uncover cutworms. If producers are digging in moisture, then they are too deep, as cutworms prefer dry soil.

“Dig first around freshly severed seedlings,” says Stanford. “I recommend spraying in the evening or at night for cutworm when the economic threshold of 3-4 cutworms per metre square is reached.”

Unlike cutworms, wireworms prefer cool, moist soil and tend to be most active in the top 6 inches of the soil. To sample for wireworm larvae, producers should mark out areas 50 cm x 50 cm and sieve the soil to a depth of 15 cm (6 inches). They should repeat this in different areas of the field to determine an average number of larvae per m². “It is important to determine if the problem is cutworms or wireworms, because there are no effective chemical controls available for wireworms in canola,” says Stanford.

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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

 

This media release is supported regionally by:

Alberta Canola Producers Commission; Saskatchewan Canola Development Commission; Manitoba Canola Growers Association; Canola Council of Canada; Peace River Agriculture Development Fund; B.C. Ministry of Agriculture & Lands.