Types of pests: Leaf suckers, chewers, borers, and gall-makers

Be they invasive or native, tree insects and diseases can cause severe damage to our native trees and forests if not correctly managed. Insect pests cause damage through sucking, chewing, boring, gall-making, and other activities that weaken trees.

Here are some common insect pests in Missouri:

Aphidstypes of pests

Aphids are small, soft-bodied insects that feed on plants’ sap using their long, slender mouths to pierce stems, leaves, and other tender plant parts. Signs and symptoms of aphids include:

  • Sticky leaves or leaves dripping sap, called “honeydew”
  • The formation of galls
  • Sooty mold

Sooty mold is a black, powdery substance that can cover leaves and twigs that grows on the honeydew left over by aphids.


Scale insects suck the sap from plant tissues. Signs and symptoms of this pest include:

  • Twig and canopy tip dieback
  • Yellowing leaves
  • Waxy, circular “scale bodies” on twigs
  • Honeydew


Bark beetles burrow under the bark of trees and will prey on both healthy and dying trees. When they feed, they may introduce pathogens that can disrupt the tree’s vascular system. Symptoms of bark beetle include:

  • White or reddish-brown pitch tubes on the outside of the bark.
  • Borer holes in the tree when the bark is peeled away
  • Flaking or holes in the bark from woodpecker foraging
  • Frass (a sawdust-like substance) around the tree and in tree crevices, an indication of burrowing
  • Browning leaves or needles

Spider mites

Spider mites are so small as to be almost microscopic, and part of the spider family. Despite their small size, their visible webs and discolored foliage makes their presence noticeable. The presence of webs is the most obvious symptoms of an infestation, along with leaf drop, loss of vitality, and yellowing leaves.

Japanese beetles

Japanese beetles (not to be confused with emerald ash borer) skeletonize the leaves of trees and shrubs, leaving them “lacey”. This can lead to partial or entire defoliation, as these beetles often feed in groups of up to 25 individuals. Japanese beetles can feed on over 300 species of plants.

Many of these pests travel in firewood so if you are camping or have a home fireplace, use it where you buy it!

To prevent an infestation of these insects, it’s critical to keep an eye on your trees. If you notice a problem, contact Hansen’s Tree Service to schedule an assessment with an ISA Certified Arborist to diagnose your trees and prescribe treatment.

Think Your Trees Are At Risk?

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