Numerous harmless tree insects live on, in, and around trees, but some are very dangerous and can cause fatal damage to the tree. Following are three main types of tree insects that cause fatal damage to trees.


  • Chewing Insects: Bagworm, Tent Caterpillar, Gypsy Moth, Cherry Fruit Worm, Japanese Beetle, Leafminers, Apple Maggot, Spring, and Fall Cankerworm.
  • Boring Insects: Giant Palm Weevil, Asian Longhorned Beetle, Elm Bark Beetle, Dogwood Borer, Bronze Birch Borer, and Emerald Ash Borer.
  • Sucking Insects: Aphids, Scale Insects, Spider Mites, Leafhoppers, and Thrips.

Spruce Adelgids

Spruce Adelgids cause damage to trees by sucking out their sap, which starts a reaction within the tree that causes galls to form.

You can typically find these insects at the end of smaller twigs on the tree. These reside within the galls formed on the tree. You can treat the infestation by removing any green galls that appear, but insecticides can provide an easier method.

Birch Leaf Miner

The birch leaf miner is a common insect that can weaken birch trees, eating their leaves and causing unsightly discoloration. Although typically not a risk to the health of the tree, over many years this insect can create more serious issues.


Aphids are a pest that can multiply into large populations on your trees. They feed on sap and can cause leaves to shrivel or curl. Aphid eggs will hatch in spring and species can appear in different colors, including green, red and black.

To rid your trees of aphids, you can use insecticides, but you can also introduce natural predators to the environment. Common predators include lady beetles and hoverflies.

Spruce Spider Mites

Spider mites can do great damage to evergreen trees. A quick treatment of topical insecticides is recommended. Some signs of spider mite infestation include single strands of webbing and small tan dots on the tree’s needles. It may also be helpful to know that mites are most active in the cooler months of spring and fall.

Some ways to ward off populations is by planting trees further apart and making sure that they are well watered.

Boring Insects

There are many varieties of boring insects, each presenting their own set of risks. Most healthy trees have natural defenses against these insects that feed on wood, but trees that are under stress may be more susceptible.

One reason why boring insects are so harmful is that with most species, their larvae feed on the tree tissue that is used to transport water and nutrients throughout the tree. This can make a tree weaker and more susceptible to further damage. These insects can also carry harmful diseases.

Some of the common boring insects include:

  • Two-lined chestnut borer
  • Emerald ash borer
  • Bronze birch borer
  • Flatheaded appletree borer
  • Pine sawyer beetle
  • Red-headed ash borer
  • Asian long-horned beetle
  • Linden borer
  • Zimmerman pine moth
  • Dogwood Borer
  • Peachtree Borer
  • Ash Borer
  • Pine bark beetle
  • Spruce bark beetle
  • Smaller oak bark beetle
  • Elm bark beetle

It is hard to detect the initial infestation of these insects, but sometimes you will notice that there are holes in the bark of the tree.

There are a few steps that can be taken to defend your trees from boring insects. You can provide the tree with fertilizer, and you can also use prescription products such as Arborceuticals™.

As with most diseases and pests, it is best if you can prevent the problem before it happens. One great way to stay on top of the health of your trees is by calling Arbor Man Tree Care. We can provide inspections and regular maintenance.