How to handle caterpillar population explosion in your yard

As Alberta deals with a boom in the tent caterpillar population, CTV News Edmonton's Miriam Valdes-Carletti sought out tips on how you can protect your trees.

Tent caterpillars are out in full force in the capital region and have some Edmontonians worried about the effect the population boom could have on their trees.

Recent weather in the capital region has helped the caterpillar population grow, and campgrounds are swarming with the insects.

• No refunds: Tent caterpillars overrunning Alberta campgrounds

Dealing with the insects can make people squeamish, but while they are mostly harmless to humans, they can be voracious eaters of your greenery.

“Caterpillars are not bad, they’re a part of the natural landscape of a forested area, they provide food to a lot of predators, so they are an important part of the food chain,” said Kevin Sproule, assistant district manager at Davey Tree Edmonton.

“It’s when they get to these really large populations that it can be a concern.”

In urban areas, trees might not survive defoliation if they aren’t healthy enough.

“There are a lot of trees that have been suffering in Edmonton for a few years because of drought and high winds, maybe they’ve got some cracks in them,” Sproule said. “It is a good idea to give your local arborist a call, for us to come out and have a look.”

Trees that aren’t as healthy as they could be can also be left vulnerable to other insects and disease if caterpillars eat away too many leaves.

If you want to remove caterpillars from your trees, Sproule suggests spraying large clumps on the trunk with a hose, using something else to knock them off or use an insecticide to help reduce the population.

“A lot of caterpillars can give you a rash if you touch them, so I would avoid touching them with your bare hands,” Sproule said.

“If you are going to go out and try and physically remove them from your tree, wear gloves.”

Shannon Gadwa, general manager for Birch Fumigators, says her company has been “very busy” dealing with the caterpillar population.

“Trees that we treat this year will be better next year, because we’re terminating the active caterpillars, as well as their eggs that they’re laying,” she said. “Boom seasons usually last two to three years, so we could see a spike again next year, or they may start to dwindle.

“Once the boom is over, then the populations will go down to nearly non-existent again for another 10 years or so.”

Sproule recommends watering trees regularly, putting down a layer of mulch during dry periods, proper pruning and fertilizing to keep trees healthy.

“Healthy trees can withstand a couple years of defoliation from caterpillars before you start to see any negative health effects,” he added.

“It’s not always necessary to do something about the caterpillars.”

The excrement from the tent caterpillars can also be good fertilizer, so in smaller qualities, the insects can be beneficial for the environment, Gadwa added.

The caterpillars should turn into moths by July, according to Parks Canada.

With files from CTV News Edmonton’s Miriam Valdes-Carletti and Hannah Kavanagh