Recovering from "Attack of the Tent Worms"

Last June, in "Attack of the Tent Worms" I shared the devastation that Tent Moth caterpillars caused here in Powell River, BC. For some unknown reason, every 5-10 years there's a population explosion. And this was our year. They prefer to eat the leaves of deciduous trees. In our case, the alders took the brunt of the attack.

Alder trees grow almost like weeds here, especially after logging companies cut down a new tract of mature firs and cedars. After vines and small shrubs, it's the alders that naturally reclaim the barren soil. They gave the caterpillars an abundant food source. Tent caterpillars, and the subsequent moths, are named for the structures they build for protection while not eating.

Here's an alder in the parking lot of the Shinglemill Marina on Powell Lake. You can see what the caterpillars voracious appetite can do in just a few weeks.

The dark spots you see are the tents attached to the now bare branches. They say a healthy tree can withstand such an assault when the six weeks of munching are finally through, and the caterpillars enter the pupa stage.


Here's the same tree on August 10. It's not back to its normal full foliage, but it's well on the way. By next spring, you won't know anything unusual happened. Look close, you can still see evidence of the tents in a few places. -- Margy