Canola growers in southern Alberta should be on heightened alert for flea beetles this spring.
Scott Meers, provincial entomologist with Alberta Agriculture, said a late, cool spring has delayed canola seeding across much of southern Alberta.
That means canola seedling development will be later than usual, and emerging crops will be vulnerable to flea beetle damage when warm weather arrives.
“The way things are setting up, we’re likely to get the warmer weather and significant flea beetle activity when the canola is still small,” Meers said. “There’s a real good chance that we could see lots of flea beetle damage when the weather warms up.”
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He said flea beetle activity was higher than normal last fall in southern Alberta’s canola growing areas.
Numbers were particularly high around Lethbridge and St Albert.
“The south had elevated levels last fall. In central Alberta and the Peace, we didn’t really get those reports.”
Flea beetle numbers were also higher than normal in southern Saskatchewan and in parts of south-central Manitoba.
Monitoring for flea beetles should begin shortly after canola is seeded.
The crop is most vulnerable in the first two weeks after emergence. The potential for damage diminishes when the plants advance past the three- or four-leaf stage.
“Certainly once you start to see emergence of the crop, you want to be monitoring for the beetles and scouting for leaf damage every two or three days,” said Derwyn Hammond, a senior agronomy specialist with the Canola Council of Canada.
“If you identify that flea beetle numbers are getting high, then you probably want to be staying on top of things every day, going out and taking a look and evaluating how much leaf area is being pitted by the feeding of the flea beetles and monitoring more closely.”
When scouting fields, farmers can assess flea beetle numbers and look for “shot holes” where the insects have bitten through leaves.
The first sign of feeding damage is not necessarily an indication of devastating infestation to come, Hammond added.
That’s because the new generation of seed treatments require the insects to eat leaf material before the insecticides take effect.
Nonetheless, producers should consider further action when they find that beetles are damaging more than 25 percent of leaves.
“When flea beetles are in high numbers and they do move in, they can do a lot of damage in a hurry,” Hammond said.
If crop damage exceeds the 25 percent mark, he recommends using one of eight registered foliar sprays.
“The 25 percent action threshold gives guys the opportunity to get organized and get that foliar application done before area leaf loss exceeds 50 percent and yield and economic losses become significant.”
