Wasp eager to take on cereal leaf beetle

Wheat, oats and barley affected | Agriculture Canada says biological control is the best method

Growers concerned about the appearance of cereal leaf beetles in their region are advised to tread lightly.

In most cases, growers shouldn’t turn to chemical controls, says Hector Carcamo, an Agriculture Canada research scientist who is working with one of the pest’s natural predators, a wasp that has been found to keep pest numbers in check.

The wasp is vulnerable to chemical controls.

“We’ve noted that in a few cases people have been rushing to spray when they actually have not reached the economic threshold,” Carcamo said.

The cereal leaf beetle, still a relatively new pest on the Prairies, appears in the spring and is active into July. First identified in Alberta in 2005, it has since appeared in Sask-atchewan and Manitoba.

The beetle didn’t appear in high numbers in southwestern Saskatchewan this year, preferring humid areas. Irrigated cereals in the Leth-bridge area have been the biggest problem area, said Carcamo.

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He also reported new invasions near Red Deer in Alberta and Brandon in Manitoba.

The pest feeds on wheat, oat and barley crops during the flag leaf stage, affecting yields.

Carcamo said growers shouldn’t spray if they’re seeing less than one larvae per flag leaf.

Previous work at Agriculture Canada has identified a wasp — Tetrastichus julis — as an effective control for cereal leaf beetle, keeping numbers below the threshold and reducing the potential need for insecticide.

“(It’s) actually one of the few cases, maybe the only one that I’m aware of, of a field crop pest where biological control is actually the primary control strategy and all other strategies are secondary and are supporting biologic control,” he said.

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Carcamo is leading a project to introduce the wasp to parts of the Prairies where the cereal leaf beetle numbers are highest.

The wasp, which will move with cereal leaf beetle populations, has been introduced to some of the sites that have reported new infestations, said Carcamo.

Officials will revisit those sites over the next two years. They will also look to determine what landscapes allow for the best establishment.

“This information would be helpful, so in the future when we relocate the parasitoid, we have a better idea of where are the best places to re-lease them,” he said.

“Eventually the wasp will become established in most of the areas, but it’d be nice to give them a boost and get them established there faster.”

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