When caterpillars invade, here’s how to fight back
Hairy little crawlers are dropping in your hair, squishing underfoot and ruining your deciduous trees.
The tent caterpillars are back and this year it seems like they’ve arrived with an invasion force.
“Every seven years they seem to peak,” says Nigel Lambeth of Campbell River Garden Centre.
Entomologists say the cycle for the western tent caterpillar is roughly every nine years with a three-year population outbreak.
This would be one of those outbreak years and it’s hard not to miss the silken tents wrapped around the tender branch ends and new leaves.
But then those white tents transform into dark writhing balls of hungry caterpillars which feed, cocoon and transform into moths, before starting the whole cycle again.
Generally, tent caterpillars won’t decimate or kill larger trees, but they’re still a stressor on plants and can defoliate small trees. More than anything, they’re considered an unsightly nuisance and despised by many a gardener.
“We stocked up on BTK because we knew what sort of year it was going to be,” says Lambeth.
BTK, or Bacillus thuringiensis, “is found naturally in the soil and is known to cause illness in various insect larvae, including caterpillars,” according to the B.C. Ministry of Forests, Lands and Natural Resources.
The bacteria, notes Lambeth, is very effective in controlling caterpillar populations as it disrupts their digestive systems. Better still, according to the ministry website, there’s, “no known toxic effects on humans or other mammals, plants, birds, fish, honeybees, or other beneficial insects.”
But there are other ways to control caterpillars which can continue the hatch through the summer.
Lambeth advises to look for the eggs which appear as a “smear of brown chewing gum” on leaves. This can be easily wiped off. Another simple method is to break off the branch ends that have nests and properly dispose of them.
A slightly more involved process requires plucking out the majority of caterpillars, but leaving behind the ones which have vivid white dots around the head.
These dots are the eggs of parasitic wasps and flies. And if you think squishing caterpillars underfoot is gross, get this, when the maggots hatch, they feed on the caterpillar’s non-essential organs so then the major organs last!
It’s all natural, Lambeth says with a grin, and the parasitic insects help keep the caterpillar populations in check throughout the summer.
Finally, he adds, it’s a good idea to give infected trees a little more water and a shot of fertilizer to encourage new leaf growth.
Last, but not least, it’s never a good idea to try burning caterpillar tents when they’re still in the tree.
You may set fire to the entire tree and surrounding grasses, and this sort of pest eradication is sure to bring a visit from the fire department.