Yuck, tent caterpillars have invaded my apple tree and I want them gone!

Based on my googling, they appear to be Western Tent Caterpillars. They make themselves visible as the leaves and blossoms come out in spring. Here in my Winnipeg front yard, I spotted them on May 15. 

This is what my blossoms should look like at this stage.

The brown moths of Western Tent Caterpillars lay eggs in the fall in a cluster that forms a cylindrical collar around a branch. It looks a like brown styrofoam with pin pricks.  I found a couple of collars on my tree that looked like this.

 

The larvae emerge and go off in groups looking for green leaves to eat. As they eat and grow they leave a silky string behind them and form an ever increasing silk tent. They huddle in the tent together and go out to eat three times a day. By June, the larvae (tent caterpillars) pupate and a week or so later the moths emerge and lay new eggs which will repeat the process next year.

They won’t kill the tree, but they might destroy enough leaves and blossoms to greatly reduce the apple harvest. At the very least they stress the trees and cause the tree to focus its energy on leaf production rather than apple production.

It’s a good idea to get rid of them as soon as you can.

What To Do About Tent Caterpillars 

If you have one or two apple or cherry trees, here’s the low cost, no spray way to deal with tent caterpillars early on. If you have multiple, huge trees this approach is not very practical, you may need to investigate other solutions.  I found this article from the Pacific NorthWest Pest Management Handbook to be quite useful.

Step 1 – Scouting

Check your trees for signs of tent caterpillars as the leaves and buds appear.  Even before then, you can look for the egg clusters on the branches. They’re pretty well camouflaged so you really have to inspect carefully.

Step 2 – Physically Remove Egg Clusters and Caterpillar Tents

Not a pleasant job, but if you don’t want your tree to be stripped of blossoms and leaves, you have to get rid of the tent caterpillars.

Destroy the egg clusters by breaking or carefully cutting them off the tree. Carefully, because you don’t want to nick, break or otherwise harm the branch.

Remove any silky caterpillar tents and caterpillars you see. I did this by cutting or breaking off tips of branches or whole sets of blossoms. It’s sad to lose the blossoms, but better to sacrifice a few than lose the whole tree to the caterpillars. 

The caterpillars leave the tent during the day to feed, it is best to destroy the tent when they are all at home – early morning, at night or during rainy/cloudy days.

Warning, when you jiggle the branch with the tent, the larvae will jump off the branch on a string of silk. Be ready to catch them in a container or plastic bag so you capture them all. Here’s a video of how I did it. I sure wish I would have remembered to put on my gloves before climbing the ladder!

Step 3 – Stay Vigilant

Continue to check your trees. They’re easy to miss when they’re little, so keep checking and removing daily until you’re sure you got ’em all.

Oh, these guys also enjoy plum and cherry trees, so check those. Other non-fruit trees they enjoy include willow, poplar, cottonwood, birch, roses and oak.

Step 4 – Check for Egg Clusters When Leaves Have Fallen

Do a thorough check of your tree branches in late fall once the leaves have fallen for egg clusters. Destroy them to break the cycle. Even if you got all the caterpillars in early spring, the moths could have flown in from elsewhere, so stay on top of things.

Okay, that’s one pest taken care of – now we need to start thinking about coddling moths and apple maggot flies. Sheesh, growing good fruit is work!

But, oh so worth it!