Grasshopper today’s top pest issue in Manitoba

Agriculture and Agri-Food Canada’s 2013 Prairie grasshopper forecast. (AAFC)

Weird weather appears to putting the lie to the age-old assertion that on the Prairies, you get either grasshoppers or mosquitoes, but never both.

In scattered pockets around the province, young hoppers are boiling underneath the grass canopy even as hordes of mosquitoes hover above creating misery for man, bird and beast.

“Currently, the biggest issue in Manitoba is grasshoppers,” said entomologist John Gavloski of Manitoba Agriculture, Food and Rural Initiatives.

In an interview last Wednesday, Gavloski said the majority of the infestations is still in the nymph stages and concentrated around the edges of fields.

The good news, he added, is that edge spraying is still an option — but the bad news is that the window for effective control with pesticides is rapidly closing.

Hot spots include the Dauphin and Ste. Rose areas in the province’s west as well as Beausejour in the east, but generally populations are higher than normal across the province.

“We’re trying to encourage people to get out and look. If numbers are high, it’s much easier to deal with them when they are juveniles than when they are adults,” said Gavloski, adding that many areas will reach the adult stage around July 20-30.

Economic thresholds are “tricky,” and in most cases amount to a “best guess” simply because the hyperactive hoppers won’t sit still long enough for a sure count.

But generally, eight to 14 adult grasshoppers per square metre is enough to cause lost yield, while for nymphs, the number is 30-35 per square metre.

“Kick around the grass, and look at the range. Don’t get too caught up whether it was 30 or 32,” he said.

Timing is everything, because once they get their wings, they are harder to kill with chemicals and be able to disperse to greener pastures.

The delayed spring and rain hasn’t dampened grasshopper populations as much as expected. Rain only kills newly hatched hoppers, and then only if the ground is flooded over for a spell. Older grasshoppers can survive a deluge by crawling up stems, and the eggs can be submerged for a long time and still be viable, he added. Also, the cool spring only delays their development.

Those not inclined to spray can hold out for the chance that a couple of weeks of hot, humid weather could create favourable conditions for a fungus that can infect grasshoppers and kill large numbers of them. But that typically only happens later in the summer, when the damage to crops and forage may already be done.

Cutworms and flea beetles were the big issues in June. Seed treatments helped fend off damage early on, but cool weather that inhibited growth allowed the beetles to overtake crops as they were still trapped in susceptible stages.

“There was some foliar spraying and even reseeding done because of flea beetles,” said Gavloski.

Although caterpillars haven’t been spotted yet, entomologists are wary of bertha armyworms due to the high capture rates of adults moths in pheromone traps, he added.

Since 1996, Agriculture and Agri-Food Canada’s Prairie Pest Management Network (PPMN), based in Saskatoon, has been helping farmers know what pests to watch for during the growing season.

The PPMN provides an in-depth analysis of insects in different parts of the Prairies and what farmers should look for as they scout their own crops for infestation and damage.

PPMN data has been collected by farmers and researchers all over the Prairie region since 1996. Prairie-wide, about 1,800 sites are monitored annually during the course of the various surveys. The network’s weekly report can be found online.

— Daniel Winters is a reporter for the Manitoba Co-operator at Oak Lake, Man.

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