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What's Eating Your Maple Trees?
This is a quick and easy guide to the caterpillars that eat maple trees, and may be damaging them. These butterfly and moth species use maple leaves as a food source, and they can sometimes multiply out of control and become a serious threat to the health of the tree.
If you do find caterpillars on your maple trees, it's important to realize that they are part of a complex web of interrelated species that have evolved together for millions of years. These caterpillars are nothing new to your maple trees! They likely do not need a lot of help from you to manage the problem.
This guide includes both pest species and less-common caterpillars that you will find on your maple trees.
For each maple-eating caterpillar species, this guide begins with The Basics:
- What is the scientific name?
- Where does this species occur?
- Will it seriously damage plants or trees?
- Does it sting or cause irritation?
- Can it be controlled without pesticides?
We also include photos, descriptions, and natural history details that help you understand your maple-eating caterpillar a little bit better.
Identification Chart for Caterpillars on Maple Trees
|Name||Identification||Reason for Concern?|
Brown, thin, looks like a stick
Cecropia giant silk moth
Huge, green, spines and bumps
Lymantria dispar (gypsy moth)
blue and red bumps on back
Yes – this is a very serious pest species
Red head, four white tufts on back
Sometimes, depending on numbers
American dagger moth
White, furry, black hair pencils
Gree, spotted, makes huge webs in trees
Yes. This species can defoliate a tree.
Moves by "looping." striped
Forest tent caterpillar
Orange and blue stripes; white spots on back
Yes, during outbreaks
Variable; striped; moves by looping
Yes, during outbreaks
Green with paler green stripes; horns front and back
This moth species belongs to the family Geometridae, which includes those caterpillars known as "inchworms" for the way they look like they're measuring when they walk. These caterpillars move by bringing their rear legs up behind their front legs, and then reaching out straight to start the next step. This motion creates a "loop" of the caterpillar's long thin body, which is why some species using this method of locomotion are also known as "loopers."
The maple spanworm is a common presence on maple trees of all kinds, but you may not notice them thanks to their remarkable camouflage. When a maple spanworm caterpillar senses that someone (or something) is nearby, it will grip onto the stick it's on with its strong hind legs and hold its body out straight at an angle from the stick. In this pose, the maple spanworm (and many of its relatives) look more or less exactly like a twig coming off the branch. Good luck finding it!
The adult moths are also perfectly camouflaged to look like a dead leaf.
Cecropia Giant Silk Moth
The cecropia moth is one of the biggest members of the Lepidoptera family in North America, so it follows that it has one of the biggest caterpillars. These beauties are a perfectly camouflaged leaf-green, but are also covered with amazing multi-colored tubercles, horns, and bumps. In my experience, one reason the caterpillars are hard to see on the food plant is that you just don't expect a caterpillar to be that big, and so paradoxically they are easy to overlook.
Read More From Dengarden
The characteristic cocoons are attached lengthwise to a strong stick or branch. The moth overwinters in the cocoon and hatches out in early summer.
In my experience, one reason the caterpillars are hard to see on the food plant is that you just don't expect a caterpillar to be that big.
Lymantria Dispar, Formerly Known as the Gypsy Moth
Lymantria dispar, the Latin name for the gypsy moth, is the name now used out of respect for the Romani people, who never asked to have such a pest named after them in the first place. By any name, L. dispar is one of the most destructive invasive species in North America. During major outbreaks, especially in the eastern US, millions (if not billions) of these caterpillars take over entire forests, where they can strip the leaves from all of the trees in a matter of days.
This insect usually attacks oak trees, but if they are not available, or the caterpillars have eaten of their leaves, L. dispar will turn to a wide variety of hosts, including maples.
White-Marked Tussock Moth
This very common species resembles the gypsy moth, but is not nearly as serious a pest. It's at home in urban areas, and will sometimes defoliate tree along city streets. They feed on a very wide variety of trees, including maple; you will often find caterpillars from several different females and of different ages on one tree.
The red head and thin hair pencils are diagnostic, but it's the four white tufts along the back, "tussocks," that give the caterpillar its common name. One very cool theory for the presence of these tufts is that they mimic the appearance of parasitic wasp cocoons. If a parasitic wasp sees those, it may not lay its own eggs, since a caterpillar that is already parasitized is not a good host for a new batch of wasp larvae.
American Dagger Moth
This species is much better known for its caterpillar than for the adult moth, which is a lovely pale gray with dark markings, but strictly nocturnal and easily overlooked. The caterpillar has thick yellow or white fur, offset by several thin black hair "pencils." It feeds on many different eastern deciduous trees, including oaks and maples, but it is seldom seen until late summer. This is when American dagger moth larvae, along with many other species, descent from their food plants and search for a place to spin a cocoon.
In the early summer, the moths hatch out, mate, and seek out suitable hosts where they will lay their eggs.
Fall webworms attack many kinds of trees, including maple trees. They are spotted caterpillars with sparse hairs that feed in large colonies. The fall webworm gets its name due to its habit of building large webbed nests in the branches of the trees on which it's feeding. Inside these nests are dozens or even hundreds of caterpillars; they feed on the tree outside the nest, and then return to the shelter to rest and molt (shed their skin).
As the summer goes on, the nests get larger and dirtier as the caterpillar poop builds up inside it. Few predators are determined enough to go through all that sticky, poop-filled webbing to get at the little caterpillars inside.
The adult moth of this species is a pretty pure white with a few black spots.
Fall webworms (Hyphantrea cunea) attack maples in mid- or late summer. The black- or orange-spotted, brown or gray caterpillars envelop themselves in white silken tents. Heavy infestations of webworms can shroud entire branches in their tents. The 1-inch pests devour the leaves’ interveinal tissues. The combined effect of webs and skeletonized leaves thwarts any chance of a good fall display.
This is a western species that is related to the maple spanworm (above). Like that species, these caterpillars "loop" their bodies when they move. As the common name of this species suggests, they eat many difference plants, including several kinds of maple trees. The adult moth is an attractive brown-orange color. It resembles a dried leaf.
For much more about this potentially serious pest, visit https://www2.ipm.ucanr.edu/agriculture/avocado/Omnivorous-looper/.
Forest Tent Caterpillar
These cool caterpillars are often found off their food plant crawling on the forest floor. They are hard to miss, with unique blue-and-orange stripes and irregular cream-colored spots along the back. Less well-known is the adult moth, which is faun-colored with a densely furry body.
The forest tent caterpillar feeds on many trees, including maples. They are not properly a tent caterpillar, since they don't make webby nests in branches. Instead, they spin mats on tree trunks where they rest when not feeding. At times, this species can undergo a population explosion; at this time, they can completely defoliate areas of the forest.
Fall cankerworms are another species of looper caterpillar that feeds on maple trees. This species prefers red maples, which otherwise seem to be protected against most caterpillar pests. The adult caterpillars are about an inch long – in accordance with loopers' other nickname, inchworms – and are variable in color and marking; individuals often have a dark stripe running the length of the body.
A heavy infestation of cankerworms can strip the leaves from an entire tree, especially a smaller, younger one; if this occurs two or more years in a row, the tree may die.
If you find one of these caterpillars on your maples, consider trying to raise it to the adult. This is fairly easy to do, if you keep it in Tupperware or a similar sealed container with plenty of fresh maple leaves and a folded paper towel on the bottom; the caterpillar will pupate among the paper towels and the adult moth will hatch in a few weeks (or spring, if you find the caterpillar in the fall). The reason for raising this species in particular is the spectacular adult moth that emerges. Called the rosy maple moth, it is vibrant pink and bright yellow, a very unusual look for a moth (or any animal).
This species rarely does serious damage to maple trees.
- Managing Pests in Gardens: Fruit: Invertebrates: Omnivorous looper—UC IPM
Information about managing pests of gardens and landscapes, from UC IPM.
- Cecropia silkmoth Hyalophora cecropia (Linnaeus, 1758) | Butterflies and Moths of North America
- Forest Tent Caterpillars Resource Page
- Caterpillars That Eat Maple Leaves | Home Guides | SF Gate
Caterpillars That Eat Maple Leaves. Maple (Acer spp.) trees account for much of the brilliant color blazing along autumn roadways and hillsides across the northeastern United States. Different species of these reliable shade trees grow across U. S. D
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.