3 Tree-Topping Categories of Tree Pests

Summary: Pests clearly love feeding on plants, but how can they cause so much damage to tall, leafy trees? This blog discusses the 3 main categories of tree pests and the 3 most infamous pests in each group. The 3 categories are: sap-suckers, wood-borers, and leaf-eaters. Green Pest Services provides safe yet efficient pest control services for homes and businesses.

Pests and plants are like oil and water: they don’t mix, no matter how much the pests enjoy the greenery. If they’re allowed to feed on the leaves and stems, the plant will eventually die off. Trees are tall and sturdy, but even they aren’t immune to this experience.

It’s common to see random insects and arachnids crawling on trees, but there are pests that specifically seek out trees as a source of both food and shelter. Let’s dive into the three main categories of tree pests and how they deal such damage to these leafy giants.

The Sap-Suckers

Signs of Infestation: curling leaves, yellow leaves, less leaf tissue, holes in leaves

We often hear about the delicious sap from maple trees, but there’s actually sap in every leaf. This is what a lot of garden pests seek when they’re crawling through gardens. The tree pests in this category have sharp, needle-like mouths that allow them to puncture leaves and drink the sap.

Sap-sucking pests are a danger for every tree and plant since they find nutritional value in each one. These tiny pests often hide on the undersides of leaves so they can constantly feed without being eaten themselves.

Aphids: If we had to name the number one garden pest, it would be the aphid. They’re common in every climate, especially when the weather is consistently hot. Aphids live on the undersides of leaves to hide from predators. They drink the sap from the leaves and stems, completely draining the plant if left uncontrolled.

Aphids lay hundreds of eggs in the fall that overwinter and hatch in the spring. As soon as the weather is consistently warm, aphids begin their work of destroying the greenery. These green pests also produce honeydew (basically their waste) as they eat. This substance not only attracts other pests (like ants) to the tree, it can also form sooty mold that ruins the leaves.

Whiteflies: You can probably guess the color of these tiny pests based on their name. Whiteflies live on the underside of leaves to hide and feed, and they usually stick with fruit trees. This means that a bad whitefly infestation can ruin both the leaves and the fruit. Whiteflies even prevent trees from producing more fruit if the pests drink too much sap!

Another downside to whiteflies is that they transmit plant viruses if they previously fed on an infected plant. If their constant feeding doesn’t harm the trees enough, a potential plant virus will. Whiteflies leave honeydew behind — just like aphids — so the sweet substance is a clue that either of them are on the tree and need to be stopped.

Two-Spotted Spider Mites: Spider mites are common garden pests, but two-spotted spider mites are also popular tree pests. Two-spotted spider mites have two dark spots and are yellow-orange in color. If you find a lot of thick, clustered webbing on the leaves, it’s a sign of spider mites. Their webs provide protection for both their eggs and themselves.

These pests live under the leaves as they drink sap and gradually deplete the trees. Two-spotted spider mites leave white or yellow spots on the leaves as they eat. They feed on a variety of trees, but they prefer fruit trees and evergreens. Considering they overwinter as eggs, it’s easy to see how two-spotted spider mites can ruin leaves once spring arrives.

The Wood-Borers

Signs of Infestation: stunted growth of tree, small holes in the wood, moisture damage to tree, lots of insects under the bark, destruction of inner bark

Wood-boring pests are not just a problem for houses and fences. They’re also a major problem for the source of these building materials: trees! These tree pests are considered to be the worst of the three groups since they stop water and nutrients from reaching the leaves and fruits of the tree, causing a slow demise.

Some of them bore into the wood to look for prey, while others like to eat or live in the wood itself. Most of these pests tunnel inside to eat the inner bark and make their way into the heart of the tree. These tree pests are even more hidden than the sap-suckers because they hide inside the tree. If the pests are left alone long enough, they will create irreversible damage.

Weevils: Tiny weevils cause major problems for any kind of wood, including the inner framework of a house. They stay near the roots of the trees and create wooden cells under the bark as their shelter. Weevils thrive in warm and humid weather, which explains why we see them more often in the summer.

Although they like to live near the roots, weevils lay their eggs in the leaves. If they find that the nearby house is warmer — or if the inner frames entice them — weevils may choose this in favor of their original tree residence. This is why it’s important to treat a weevil problem early on: it’s easier to eliminate them when they’re in a tree and not eating your house!

Carpenter Ants: Surprisingly, carpenter ants aren’t the most destructive to actual trees. In fact, a carpenter ant invasion is a warning sign of preexisting damage to the tree. They prefer trees that are old, decaying, and/or rotten. Any tree with damage is a target for carpenter ants, which explains why they also invade fencing if it’s already worn down.

Carpenter ants often invade trees after a major storm because the damp wood is softer for the ants’ mouths to chew through. Since the wood is already damaged, carpenter ants are not super dangerous to trees. If you see a ton of these ants crawling on a tree, the tree probably had some decay already before the ants arrived.

Bark Beetles: The appropriately-named bark beetles don’t just hang out on trees and munch on bark. They actually want the inner bark, which is accessible by drilling through the outer layers. One of the obvious signs of bark beetles is finding frass around the base of the tree. These are their droppings that look very similar to sawdust, similar to termites.

Bark beetles don’t get a free pass: trees fight back. They create pitch — white or red-brown resin — that fights bark beetles. The color of the pitch reveals the tree’s success. White means it repelled the beetles, and red-brown means the beetles won. Besides the damage, there’s another issue. Woodpeckers love bark beetles and will peck at the tree to find their favorite snack!

The Leaf-Eaters

Signs of Infestation: scalloped leaves, holes in leaves, stunted growth, silvery leaves, distorted leaves, lots of holes in leaves, yellowing leaves

Sap-suckers aren’t the only tree pests that tree leaves need to worry about. They also have to deal with pests that chew through the leaves themselves! A tree can survive having several of its leaves eaten and will usually just bounce back. But if these pests stay on a tree for most of the year, the tree will have stunted growth and lasting health issues.

Some pests like to eat from the veins outward, while others prefer to just snack on the edges of leaves. Whatever they choose, it’s not good for any tree to have pests eating their leaves for a long time. It’s best to catch these tree pests early in the infestation. The sooner that a leaf-eating pest invasion is stopped, the less damage your tree will have!

Bagworms: These pests are not just a funny-looking bug to catch in Animal Crossing: New Horizons. They’re also a major tree pest, especially in spring and summer. Bagworms are just moth caterpillars in their cocoons, but they are more mobile than other caterpillars. They can move inside the bag or transport the whole bag by ballooning with their silk.

Bagworms attach to branches or leaves with silk, then eat the leaves touching their bags. In large numbers, they defoliate trees. Their main targets are evergreens and conifers. It’s hard to find bagworms until after they infest a tree. Infestations occur when female bagworms lay hundreds of eggs in their bags. But it’s easy for us to pick them off by hand, so that’s a win!

Japanese Beetles: Japanese beetles can defoliate a tree after just a few weeks of eating leaves. They destroy the most vital leaf parts by eating around their veins. These shiny beetles are found on maple trees, fruit trees, crape myrtles, willows, and birches. If you have any of these trees, you may want to keep any eye out for shiny beetles trying to ruin the leaves.

There are actually some trees that repel Japanese beetles, which is a ray of hope if the trees are in your yard. Hearty trees, like spruce and dogwood, repel the beetles. Flowering trees, like magnolia and lilac, also drive these beetles away. You don’t have to plant these trees to avoid Japanese beetles, but it helps with prevention if you already have some in the yard.

Gypsy Moths: This invasive species defoliates any trees they steadily eat from, but gypsy moths don’t always kill trees if they’re eliminated in time. Gypsy moths cause problems when they’re in their larval and pupal stages. If you thought you knew hungry caterpillars before (á la Eric Carle’s book), gypsy moth caterpillars are some of the hungriest caterpillars ever!

Gypsy moths are only known to ruin trees if they feed upon the same one for many seasons. Coniferous trees are especially vulnerable to leaf-munching. Dry seasons are great for gypsy moths since their fungi nemesis needs humidity. If you find tiny moth eggs on leaves, remove the leaves immediately. It’s easier to get rid of pest eggs than to eliminate adult flying pests!

Save the Trees with Green Pest Services!

No matter which pests are plaguing your trees, pest control is always a superb solution. Some of these pests can be physically removed by simply picking them off of the trees, but this is a temporary solution. It’s even less effective if there are more pests hidden in the branches or under the bark that can’t be reached with store-bought sprays.

At Green Pest Services, our experienced technicians know exactly where to look for these tree-loving pests and how to ensure they don’t ruin your yard. We don’t waste time with ineffective treatments that fail to target the root of the issue. Our personalized treatment plans provide long-lasting solutions for your tough pest problems. Contact us to learn more about our services and how we can keep your yard full of trees, not pests.

Citations

Arbor Day Foundation. (2018, May 25). Common tree pests and how to spot them. Arbor Day Foundation. Available at https://arbordayblog.org/treecare/common-tree-pests-and-how-to-spot-them/ (Accessed on January 22, 2025).

Ardoin, J. (2022, June 17). How to protect your trees and shrubs from Japanese beetles. Lawn Love. Available at https://lawnlove.com/blog/pest-control-how-to-protect-trees-shrubs-from-japanese-beetles/ (Accessed on January 22, 2025).

Bagworms on trees and shrubs. (2022, May 17). University of Maryland Extension. Retrieved January 22, 2025, from https://extension.umd.edu/resource/bagworms-trees-and-shrubs

Barnes, E. (2018, June 19). Gypsy moth: Don’t panic, be vigilant, get organized. Purdue Landscape Report. Available at https://www.purduelandscapereport.org/article/gypsy-moth-dont-panic-be-vigilant-get-organized/ (Accessed on January 22, 2025).

Hahn, J., Weisenhorn, J., & Bugeja, S. (2022). Japanese beetles in yards and gardens. University of Minnesota Extension. Available at https://extension.umn.edu/yard-and-garden-insects/japanese-beetles (Accessed on January 22, 2025).

Hahn, J. & Wold-Burkness, S. (2019). Aphids in home yards and gardens. University of Minnesota Extension. Available at https://extension.umn.edu/yard-and-garden-insects/aphids (Accessed on January 22, 2025).

Hahn, J. & Wold-Burkness, S. (2020). Two-spotted spider mites in home gardens. University of Minnesota Extension. Available at https://extension.umn.edu/yard-and-garden-insects/spider-mites (Accessed on January 22, 2025).

Nauman, F. (2022, September 9). Common pests that damage trees. Lawn Love. Available at https://lawnlove.com/blog/common-pests-that-damage-trees/ (Accessed on January 22, 2025).

Purcell, L. (2013, July 9). Question: Are carpenter ants harmful to my tree?. Purdue Forestry & Natural Resources. Available at https://www.purdue.edu/fnr/extension/question-are-carpenter-ants-harmful-to-my-tree/ (Accessed on January 22, 2025).