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Vigour Response Might Be Better Flea Beetle Control

Three years of field research conducted by Agriculture and Agri-Food Canada on canola treated with Helix XTra appeared to initially point to a vigour response to cold soil, said Agriculture and Agri-Food Canada researcher Bob Elliott.

“We see improved vigour in terms of seedling emergence and crop establishment and we also see it in terms of shoot growth (with treated early-seeded canola),” he said from his office in Saskatoon.

“We see those early-season benefits translate into significantly higher yields. And we all know canola can compensate, particularly when you seed early, but those differences that we see earlier on in the growing season are carrying right through to yield.”

But when tests were done in the laboratory there was no significant difference in vigour or yield between treated seed subjected to cold conditions and treated seed grown under normal conditions. That left Elliott and his colleagues puzzled.

“The hypothesis we’re working on now is that we suspect in canola that the improvements we see in vigour (in the field)… are likely stemming from those differences in flea beetle damage,” he said.

It could be that flea beetle damage to canola grown from untreated seed is hurting yields more than expected. It’s almost a moot point since nearly all canola seed is treated with an insecticide anyway.

In field tests the untreated canola seed suffered 15 to 20 per cent damage from flea beetles. The economic threshold, where treating pays, is 25 per cent.

The flea beetle damage to the treated canola ranged from just four to eight per cent, Elliott said.

“Reducing that (flea beetle damage) by 10 per cent with these treatments appears to be having a significant effect on establishment and on growth,” he said.

What was thought to have been a boost in seedling vigour might really be the result of less flea beetle feeding.

When it’s cold and windy flea beetles tend to stop feeding on seedling leaves, but Elliott suspects they might be chewing on stems at soil level.

“I suspect canola seedlings are less tolerant to damage to their stems than they are to cotyledons and leaves,” Elliott said. “We could be missing that with our damage assessments.”

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Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.

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