Seven garden army: nasty species of cutworm attacking Yukon gardens

An infestation of black army cutworms in the Takhini River valley and Lake Laberge area has some residents keeping a close eye on their gardens.

An infestation of black army cutworms in the Takhini River valley and Lake Laberge area has some residents keeping a close eye on their gardens.

There are several species of cutworm native to the Yukon, said Randy Lamb, an agrologist and insect specialist with the Yukon government’s agriculture branch.

The worms target leafy plants and earn their name through their destructive habit of feeding. They cut seedlings off at the base and devour them, leaving only a little green nub poking up out of the soil.

“That’s why they call them army cutworms … they move en masse,” he said.

Most species feed independently but black army cutworms have an unusual quirk. The pests can amass by the thousands in a squirming black mass, feeding and moving together, like an actual army. This unusual behaviour is a protective adaptation against predators such as robins. Moving in such huge numbers reduces an individual’s chance of being eaten, said Lamb, because even a very hungry bird can only eat 20 or 30 bugs at one time.

“People with market gardens should be on the lookout,” he said.

Black army cutworms do not always amass in this way, said Lamb, but only when there is a sudden increase in the population, similar to lemmings or locusts. The insects have exhausted their usual food source — precisely what they eat in non-swarm years is not entirely known — and are on the move in order to feed.

“Pest of the year, that’s what I’m calling it,” said Lamb.

These population increases are part of a natural cycle, said Lamb, occurring every every five to 10 years. The last reported cases of outbreaks like this were in the late 1990s.

“(The cutworms) have been there all along,” he said. “It’s just that you don’t usually see more than five or 10 at a time.”

“If you find a hot spot, there can be thousands.”

The worms emerge in late April or early May and finish their feeding in mid-June. Lamb expects the cutworms to be finished their feeding cycle in the next week or so.

Lamb said there are environmentally-friendly options for pest control, such as specialized bacteria that only target moth larvae. He warns against using standard pesticides, because by the time they are applied the worms will either have moved on or pupated.

Black army cutworms are black with a grey stripe and active during the day. What plants the insects find most attractive during this swarming period is unknown, said Lamb. The worms seem to prefer the Takhini and Shallow Bay areas.

If you find the worms in your garden, you can call Yukon Agriculture at 667-5838 to report what kind of plants they are feeding on. This information can be useful in predicting and managing future outbreaks of black army cutworms, said Lamb.

Contact Lori Garrison at lori.garrison@yukon-news.com

Just Posted

UPDATED: City of Whitehorse issues stop work order on proposed downtown condo

Condo development must wait for application to be reviewed

Old Crow woman successfully appeals assault sentence that was based on her unrelated marijuana use

In his decision released Jan. 16, Justice Ron Veale called the original sentence “unfit”

Whitehorse council puts an end to quarry plans

City council unanimously votes to reject OCP amendment to allow for quarry

Team Scoffin to represent Yukon at 2018 Brier

‘It’s a thrill. It’s a dream come true’

Updated: Whitehorse daycare abruptly shuts down, leaving parents scrambling

Owners of Cheeky Monkey daycare said they had to close Jan. 13 because the CRA seized their assets

The week in Yukon mining

Goldcorp re-submits Coffee plans, Mount Nansen sale looms, Kudz Ze Kayah comments open

Ice, ice, baby: scaling a frozen Yukon waterfall

‘There’s a really transformative affect with adventure’

Yukon history is picture post card perfect

The most interesting gift I received at Christmas this year was the… Continue reading

Contentious Whitehorse quarry proposal raises city hackles

‘We’ve had concerns from the get-go on this one’

Whitehorse time machine

Yukon’s capital added 10,000 people over the last three decades, no YESAB application needed

How to make sure your car starts in the cold

It’s about more than just making sure your plug works

Whitehorse fuel delivery company fined $1,100 for Rancheria crash

The Crown stayed two other charges against the company related to the Aug. 7, 2017, crash

Most Read