Western Producer reporter Bill Strautman previews the Alberta pest situation for the coming crop year. The next instalment will provide a prairie-wide pest outlook and offer tips on prevention.
LETHBRIDGE – Grasshopper numbers in Alberta should remain low for 2007, much like they did in 2006, says Scott Meers, a pest risk management specialist with Alberta Agriculture in Brooks.
Meers reviewed the risk posed by different insects at the recent Agronomy Update in Lethbridge.
Cabbage seedpod weevil
Meers said the cabbage seedpod weevil overwinters as an adult, moves into canola as it starts to flower and lays its eggs in the developing pods, where the larvae feed.
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It then bores out of the pod, drops to the soil, pupates and comes out as an adult in the fall.
“We’re mostly concerned with the damage the larvae does inside the pod. If you’re a farmer and your canola is the first to flower in (high risk) areas, it’s the worst for cabbage seedpod weevil. For those of you who like to seed your canola early, if you’re south of Highway 1, you need to be scouting the crop as it comes into flower.”
Bertha armyworm
Bertha armyworms overwinter as pupae in the soil, emerge as moths in the summer and lay eggs. The larvae are the damaging stage.
“If your field starts to go white, you’re way too late,” Meers said.
“Bertha armyworm is driven largely by biological factors. We tend to see a two to three year outbreak in a particular area and then the numbers tend to back off.”
He said the Peace River district saw significant spraying for bertha armyworms in 2005, but that population has since crashed. In 2005, there was some spraying in the Vermilion and Wainwright areas.
Hot spots in 2006 included Edmonton, Drumheller, Milo, Taber and Foremost – areas where there haven’t been bertha outbreaks for years.
“For 2006, everyone with the exception of the Peace is going to really have to pay attention to the forecast maps as they develop through the season. But it doesn’t matter how many traps we put out …. There’s no substitute for you going out and checking your fields.”
Wheat stem sawfly
Meers said the wheat stem sawfly surveys indicate the pest will be found this year in east-central Alberta, southern areas around Foremost and Milk River and near Vulcan.
“This is substantially down from what it has been, but I don’t think we’re out of the woods. If we get a series of dry years we’re going to see a fairly quick rebound in the sawfly populations.”
Meers said a substantial acreage of the solid stemmed wheat Lillian was seeded in 2006. With rainy, cool conditions at stem elongation, the amount of pith in the stems was reduced, making it difficult to get a good idea of the varietal performance in reducing sawfly attack. However, yield reports for Lillian were good.
Wheat midge
Meers said surveys for wheat midge involve washing out soil samples, doing pupae counts and then making projections.
“We have indications of midge problems all the way down to just north of Calgary, so we will have to expand our sampling in the spring. Look for a preliminary midge map sometime in April, with a final map in May that encompasses everything north of Highway 1,” he said.
Field checking for midge requires specific conditions such as low wind and should be done just before dark. Meers said farmers with large acreages have difficulty scouting all their fields.
“I think we have to come up with something better as far as monitoring,” he said. “There is some work being done with a pheromone, but results from (2006) were a little bit iffy.”
Meers said producers have to watch for midge imposters when scouting. One fly is a dull orange instead of a bright orange and while about the right size, it looks more like a small housefly than the mosquito-like midge. It also sits on the plant differently.
“The midge will orient on the plant head up, while (the other) will orient sideways or head down.”
Cereal leaf beetle
Cereal leaf beetle was discovered in 2005 and Meers expects to see damage in 2007.
“I encourage you if you’re farming south of Highway 1 to pay close attention to the insect and the damage symptoms because we will start to see it in the next two to three years.”
Pea leaf weevil
Meers said a survey in 2000 found pea leaf weevil only in the Lethbridge area.
“In 2006, every sample we did south of Highway 1 we’re seeing it. The insect has established itself throughout all of southern Alberta now.”
Spring flights were much earlier than in previous years and populations were higher. No pesticides are registered for pea leaf weevil control and producers were unsure of thresholds or which unregistered product to use, he said.
Low pea yields in some areas were attributed to damage from weevils.
Hessian fly
Meers said Hessian fly has caused concern around Drumheller, but he added he has never seen it two years in a row in the same place.
“We have a lot of parasites that like the Hessian fly. What I think is happening is we’re getting some confusion with sawfly,” he said.
“You want to peel back the leaf sheath and look for the little flax seed-like puparium in the fall. That indicates it’s truly a Hessian fly. Sawfly damage is distinctly different, with a cut stub remaining after the crop lodges.”
Cabbage butterfly
Meers said cabbage butterfly is never a problem two years in a row, but there was a big bloom of these insects last year.
“It’s much more of a concern in horticultural crops than in canola. I think we have to be careful including those in our counts because they don’t damage canola at the same level as bertha armyworm. I don’t think they’ll be a big issue next year.”
Alfalfa blotch leaf miner
Meers said alfalfa blotch leaf miner was a new pest for Alberta in 2006.
“It does a comma-shaped mine in the leaf, then produces polka dot poke holes across the leaf from adult feeding,” he said.
“It’s established in Alberta, in Brooks. Everywhere else where it’s established, beneficial insects have been brought in to keep it under control. If we don’t find this beneficial insect, we’ll look at bringing some beneficials in to Alberta.”
“That population had sustained itself and there was spraying again (in 2006). There’s indication that the population now has a lot of disease issues and it should crash.”
