top of page

Are Caterpillars Considered a Pest?

close up of a caterpillar in a tree

Are caterpillars pests? This article will explain whether or not these seemingly harmless insects are pests and how you can manage overpopulation.

Alberta is home to over 170 species of butterflies. Butterflies are not only enjoyable to have in your backyard, but they are essential pollinators that will benefit your garden. Before you can have butterflies in your backyard, those butterflies start as eggs that turn into caterpillars. But did you know that not all caterpillars turn into butterflies? Some of these caterpillars can be invasive and dangerous to your tree's health. Caterpillars feed on the leaves of trees and plants to grow. In large enough numbers, they can cause havoc in your yard. Check out this guide to caterpillars to help you understand when to treat them as pests.


The caterpillar stage of the moth and butterfly life cycle is where they need to eat and grow to prepare their cocoons to transition into adults. Depending on the species, caterpillars might eat many parts of plants including leaves, stems, and fruit. Their voracious appetites can cause so much destruction that it kills your plants.

A single caterpillar can eat one square metre of leaves as it goes from being newly hatched to ready to cocoon. So, an infestation can result in a tree being stripped of its leaves in days. Caterpillars completely eating through leaves and leaving trees or plants bare is called defoliation.

Defoliation can weaken a tree over time. As a result, your trees can be more susceptible to other pests. Without dealing with caterpillars, you could lose your tree and need it removed.

Managing Caterpillar Overpopulation

One of the most crucial steps to managing caterpillars is to catch them early. Caterpillars can get more destructive as they grow and near their time to cocoon. Here are three steps to help you protect your yard from these pests.

Identifying Caterpillar Infestation

Caterpillars are easier to control than other pests because they don't reproduce as quickly. Some moth and butterfly eggs hatch only once a year, while others hatch seasonally. Most caterpillars hatch in the spring, but it's best to know the problematic species in your area so you can catch them promptly. During the periods before and while they hatch, you'll want to monitor your trees and plants and look for signs of caterpillars. You can look for eggs on leaves, especially where you might have seen butterflies or moths. Also, keep an eye open for damaged leaves, especially near the edge and for caterpillar poo, as they indicate you have caterpillars.

Prevention and Control Steps

You can spray pesticides on your plants to kill caterpillars, but often these pesticides also kill helpful bugs. Instead, try to combat caterpillar infestations at the source by removing leaves with eggs to break the life cycle or manually removing caterpillars from trees. You can also use nets or burlap to keep them off your plants.

Attracting Caterpillar Predators

Caterpillars have some natural enemies, including parasitic wasps and flies. Predators like lacewing, damsel bugs and ladybugs can also help control caterpillar populations. You can attract beneficial bugs with the right trees and shrubs.

Attracting these other bugs is an organic, efficient, and low-effort way to control garden pests. A variety of insects will create a healthier ecosystem where your plants and trees can thrive.


Caterpillars may sometimes turn into beautiful and beneficial butterflies, but too many of them can prove disastrous for your trees. Caterpillars can cause defoliation, preventing your trees from getting essential nutrients and energy to stay healthy. Managing the caterpillars in your yard requires vigilance and planning, but the sooner you control them, the better off your trees.

What other pests should you keep an eye out for to protect your trees? Check out our guide to beneficial bugs and harmful pests. If you need a professional to inspect your trees, trim branches or remove an unwanted tree, call All Season Tree Service today!

Located in Edmonton, we serve all surrounding cities including Sherwood Park, Beaumont and Fort Saskatchewan.


bottom of page