another perspective on tent Caterpillars

Love a Cedar Tree? Thank a Caterpillar!
It’s that time again… the tent caterpillars are back!

We get questions about tent caterpillars every day at Bayview Farm & Garden as we head into the upswing of their seven-to-nine year cycle. It’s amazing how many caterpillars there can be. Longtime Whidbey Islanders may recall 1985, when cars were skidding on the streets because of the thickness of caterpillar bodies. 

We can show you how to control caterpillars in your garden and protect plants in a non-toxic way, but it’s also good to take a moment to appreciate our creepy crawly neighbors and the meaningful place they hold in the biosystem. 

Their host plant is the Red Alder (called “red” because of how they look in the spring when the buds are swelling). In the years when tent caterpillar numbers are large, they all but completely defoliate the alders. This opens up the forest floor to sun, rain and air circulation. The fallen insect frass (caterpillar poop) provides rich nutrient to the baby conifer seedlings and saplings.

When you hear the raining sound of something that isn't rain, it’s Mama Nature fertilizing her garden. During this time, conifers enjoy a huge growth spurt and get a boost past the understory brush. Alders help prepare the ground for the royalty of the great coniferous forest, primarily Douglas Fir, Western Red Cedar and Western Hemlock. Alders take nitrogen out of the air and deposit it into the soil (magic, right?) If you pull a baby Alder seedling from the ground and look at the roots, you can see the little nitrogen nodules. 

However, when caterpillars exit their nests, they start to eat and never seem to stop. When they leave the Alder forest and head into gardens, their favorite treats seem to be the leaves of apple and cherry trees and roses, but anything leafy in your veggie garden will do.

So while we do need to protect our gardens and plants, some perspective on this amazing little creature may help us get through caterpillar season with greater understanding of the place we live.

By the way, if you see a little white dot on the back of a caterpillar's head, that is an egg from a beneficial predatory wasp, whose population ebbs and flows opposite the tent caterpillar. You might want to leave it alone as the wasp has plans for this one...but that's another chapter...

Maureen Murphy
Bayview Farm & Garden

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