Dry heat, early spray keeps icky worms away

It’s not just your imagination, Winnipeg has dodged cankerworm season.

For the rest of the summer, residents can relax under tree canopies without worrying about finding the green inchworms crawling in their hair or on their backs.

As he strolled through Munson Park on Wellington Crescent Wednesday, with his eight-year-old border collie, Apollo, in tow, Wolseley resident Jarvis commented on the healthy leaves on the elm and oak trees.

“This year is hardly bad, sometimes the trees look like lace,” said Jarvis, who declined to give his last name.

Owing to hot and dry weather, the City of Winnipeg was able to complete its cankerworm spraying schedule on Monday, putting an early end to the crawlers’ threat this season.

Some neighbourhoods, such as River Heights and Crescentwood, had an increased amount of worm larvae.

David Wade, the city’s superintendent of insect control, said that’s where crews targeted their efforts.

Jarvis said when he moved to Winnipeg from Toronto 20 years ago, he was warned about the cold weather, wind and mosquitoes — but not the worms.

“It’s only when they’re at their peak that I find them annoying. I don’t like what they do to the trees,” he said.

Leaves on some of the trees in Munson Park had a few chunks eaten out of them, which is a signature of cankerworms and forest tent caterpillars that wreak havoc on Winnipeg foliage some years.

Cankerworms, which are small and green, and forest tent caterpillars, which have pale teardrop shapes on their back and blue bands on their side — are enemy No. 1 to Winnipeg trees.

The natural life cycle of the worms includes two to seven years of high population followed by several years of low population.

Wade said this year, the worms were spread across the city in lower numbers.

“Winnipeg has like three or four different species that can get high enough numbers that they become a pest, but right now it just seems that all of them are in their low stage,” he said.

Despite their resiliency to all types of climate, Wade assured pedestrians they will not need to watch for the insects during outdoor activities this summer.

“We had the benefit of the dry weather and we were able to do a good (spraying) program this year,” he said.

They’ll be back: entomologist

Entomologist Taz Stuart said the relief won’t last, they will be back with a vengeance in a few years.

Stuart, the city government’s former entomologist and current entomologist and owner of Taz Pest Control, estimates the worms will be back when their life cycle is back at its peak.

“During some years, you’re going to see a tree completely defoliated by the cankerworms,” he said.

Preventative measures, such as tree banding, have helped to nearly eradicate the pests in some neighbourhoods.

Ian Dyck, the operations manager at Schmidt Tree Banding, said the company has had a massive increase in the use of tree banding to control worm populations.

“A lot of our longstanding customers in north River Heights have been banding entire neighbourhood blocks and it pretty much eradicated cankerworms in those areas. They just don’t seem to be the problem there anymore,” Dyck said.

Dyck recommends banding in the fall to protect trees from cankerworms which lay eggs that hatch in the spring.

Fewer mosquitos, but still West Nile risk

Another positive development of Winnipeg’s balmy weather is the marked decline in the mosquito population. However, there is no reduction in the risk of contracting the West Nile virus.

The species of mosquito that carries the illness thrives in hot, dry weather and lays low in grassy areas.

“This type of weather is their Candyland,” Stuart said.

Manitoba has detected two cases of human West Nile virus, which were related to travel, this year.

In May, the city began its pre-emptive mosquito larviciding, but has yet to conduct any fogging for adult mosquitoes.

The treatment would only be initiated if trap counts and other city guidelines are met.

The city’s mosquito count averaged two per trap as of June 13, which is much lower than previous averages for this time of year, Wade said.

Spraying is initiated when more than 100 female adult mosquitoes are found in one or more quadrants of the city and there’s an average of at least 25 female mosquitoes per trap on two consecutive nights.

To ward off West Nile virus-carrying skeeters, Stuart urged residents to use repellent and avoid going out atdusk and dawn, when mosquitos are most active.

nicole.buffie@freepress.mb.ca