Alberta agronomists are seeing bertha armyworms in the field, but the pest hasn’t reached economic levels in most areas yet.
Agronomists across the province shared information Wednesday during a weekly Twitter chat organized by Shelley Barkley and Scott Meers of Alberta Agriculture and Rural Development.
Meers and Barkley scouted about 25 fields in the Vegreville and Innisfree areas. Some fields were above economic thresholds for bertha, but not consistently, Meers wrote.
Gregory Sekulic, agronomist with the Canola Council of Canada at Grande Prairie, reported seeing low numbers of bertha armyworms in the south Peace. The armyworms are about one centimetre long right now, he tweeted.
Keith Gabert, Canola Council agronomist at Innisfail, reported bertha armyworms were sparse in most fields around Altario. But one field in the area had reached threshold levels.
Kendell Malenchak, agronomist with Providence Grain Solutions at Viking, wrote she’d heard of bertha armyworm in the Viking area, but the pest hadn’t yet reached thresholds.
Scouting and controlling bertha
Even though bertha armyworms may not yet be at economic levels, Malenchak encouraged farmers to keep scouting their fields.
The most recent Canola Watch points out individual canola fields can still see economic damage even if the regional bertha armyworm threat is low. Bertha armyworms are now starting to feed on the lower canopy, the newsletter states. As the lower leaves drop, the worms will start feeding on pods, causing economic damage.
To scout for bertha armyworm, knock the worms to the ground by shaking the canola plants hard. Farmers can then carefully count the worms in each square metre, moving leaves and dirt clumps to make sure no worms are missed. By multiplying the count by four, farmers will have a threshold.
Small bertha armyworms are tough to see, Meers wrote, so farmers and agronomists should wait until the worms start moving before counting.
Meers wrote he was amazed by how small the bertha armyworms were around Vegreville right now. He suggested waiting until the worms are at least three-quarters of an inch long before spraying, as they may still fall to disease. Economic thresholds depend on canola and insecticide prices, but Alberta Agriculture has guidelines for thresholds.
Meers also shares tips on scouting for bertha armyworm through this YouTube video.
Slugs in the Peace
A farmer from the Tangent area reported slugs to Meers and Barkley through Twitter. Slugs will feed on canola crops.
The grey garden slugs around Tangent are an introduced species, Meers explained.
“We have few good options for slugs,” he wrote, explaining there is no chemical to control the mollusks.
Though tillage has been suggested as a way to control slugs, “I would be wary of the trade-off between moisture loss and slug control,” Meers tweeted.
In a previous Canola Watch issue, the Canola Council stated tillage is not a proven solution, and doesn’t remedy this year’s slug problems.
The Alberta bug chats are held each Wednesday at 10 a.m. on Twitter. Farmers and agronomists can join the conversation, or send questions throughout the week, by using the #ABbugchat hashtag.
— Lisa Guenther is a field editor for Grainews at Livelong, Sask. Follow her @LtoG on Twitter.