As a homeowner with trees on your property, you may sometimes see groups of bugs laying together on the bark or leaves. Many insects aren’t harmful to trees and can even be good for them, but bug clusters can be a sign of pests that need to be dealt with. Learning about common tree pests and clusters will help you find problems and fix them.
What Causes Bug Clusters on Trees?
A cluster refers to things grouped closely together. Bugs may form clusters on trees for various reasons:
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Feeding: Many pests that eat leaves and suck on sap gather in groups to eat. This includes aphids, scales, caterpillars, beetles, and more. As they eat leaves or suck on sap, they stay still in a clustered formation.
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Defense – Some insects cluster together as a defensive strategy. Caterpillars may build silky nests called tents in trees to live and feed communally. The tent provides protection from predators and the elements.
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Reproduction – Certain insects cluster for breeding purposes. Gypsy moth females lay yellow egg masses on tree trunks containing hundreds of eggs. Emerald ash borer females lay eggs in bark crevices in dense clusters.
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Overwintering – Some pests seek protected places in trees to ride out the winter in dormant clusters. Scales attach to bark and remain immobile during winter months. Tent caterpillars’ egg masses overwinter on branches.
Common Tree Pest Clusters
Here are some of the most prevalent bug clusters that homeowners may find troubling trees:
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Aphids – These sap-sucking insects feed in dense groups on stems and the underside of leaves. Look for white casts, sticky honeydew, and growth distortions.
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Scale insects: When these small, immobile pests get on twigs and leaves, they leave behind crusty or waxy bumps. Sooty mold may also be present.
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Tent caterpillars – Silky nests in tree branches house groups of caterpillars that feed on leaves. Defoliation may occur.
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Gypsy moth caterpillars – Mass clumps of yellow eggs on tree trunks signal future infestations of destructive leaf-eating larvae.
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Emerald ash borer – Clusters of eggs laid in bark crevices by this invasive beetle lead to larval feeding and tunneling under the surface.
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Bark beetles – These pests carry fungi as they bore into bark in mass attacks. Look for boring dust and pitch tubes on the trunk.
Managing Pest Clusters
If you spot a concerning cluster of insects on your trees, there are ways to control them and reduce damage:
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Identification – Correctly identifying the pest is key for effective treatment. An arborist can help diagnose the problem bug.
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Monitoring – Keep an eye out for early signs like egg masses to catch infestations before they escalate. Sticky traps can help monitor pests.
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Targeted sprays – Applying insecticides directly on clusters or affected areas can eliminate pests without harming beneficials.
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Biological control – Releasing or attracting natural predators like ladybugs and parasitic wasps can provide natural pest control.
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Dormant oils – These oils smother overwintering pests and eggs when applied during tree dormancy.
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Removing alternate hosts – For pests like gypsy moth, eliminating preferred hosts like oaks nearby can deter infestations.
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Tree health – Keeping trees vigorous through proper watering, mulching, and pruning makes them more resistant to insects.
With close monitoring and prompt targeted treatment, you can manage pest clusters and prevent severe infestations on your trees. Reach out to an arborist if you need help assessing and resolving any insect issues. A few bugs are bound to find your trees, but stopping them before they multiply and spread will keep your landscape healthy.
Common Spring Tree Pests in the Northeast: Signs & Symptoms
The Northeast is home to quite a few insects that can harm trees.
Read through each symptom and it will help you narrow down your potential pest problem.
Pitching and Holes on Bark, Galleries Under Bark
Seeing small holes in your tree and wondering, “What bug is killing my tree?”
Holes in your tree bark or damage under the bark are usually a sign of some sort of boring insect-like one of these:
- Bark beetles- Bark beetles tunnel below tree bark forming galleries. They are usually small and reddish-brown to black. Pathogens can be passed from tree to tree by some species of bark beetles.
- Flathead borers—These are beetles that eat trees that are dying, stressed, or already dead. Adults tend to be torpedo-shaped with a metallic coloring. The holes they make in trees are full of frass, which is bug poop.
- Borers with round heads: These are beetles, and their antennae are usually longer than their bodies. They can get up to 2 inches long, which is longer than flatheaded bombers. They also attack trees that are stressed, and their tunnels have frass in them.
- Clearwing moths: larvae of clearwing moths bore holes in tree bark and push frass out of the holes they make. Tunnel openings can be found by small piles or a light dusting of frass. The clearwing pupal cases can sometimes be seen sticking out of the bark.
Giant Stick Insect Walks on a Tree || ViralHog
FAQ
What does a bug-infested tree look like?
An infestation of pests often leads to the creation of small or large holes in the trunk or branches of a tree. These holes are made when pests like bugs and rodents chew through the wood, leaving behind a powdery substance at the base of the tree.
What does it mean when you see a swarm of bugs?
Insects swarm for a variety of reasons. Sometimes, it’s to make sure the predators in an area are too full to eat everyone. Sometimes, it’s just because they’re the most common insects in the area. Other times, it’s not really because they’re common but because they feed on a plant that grows really close to people.
How do you treat a bug infestation on a tree?
Sometimes the best treatment is to simply leave the tree alone. Sometimes it means spraying or injecting the tree with chemicals that won’t hurt it, cutting off any branches that are damaged, or even cutting the tree down.
How to get rid of scale bugs on trees?
Conserve natural enemies and kill armored scales on infested trees by using a biorational material like horticultural oil. This material works by smothering scales. Unlike other conventional pesticides, this material can kill armored scales after they have settled while the scale body is still somewhat clear.