Tree careTree Pestsemerald ash borer sits on a leaf

Top Tree Pests Arborists are Seeing in St. Louis

In the season of spring, it’s common to see insects moving out and about. While looking at your trees, you may spot pests wandering around and in your trees. These are three of the most commonly seen tree pests seen in St. Louis.


Scales are considered one of the more common groups of pests that attack plants. They’re often seen in trees, but can also be found in shrubs or even indoor plants. From the moment they’re out of their eggs, they’re mobile. They’re called “crawlers” in this stage and are extremely small. These insects are hard to control, and can range from completely harmless to incredibly damaging to trees or other plants. 

You can try to spot these scales by noting symptoms on your trees. A few noticeable signs can include:

  • yellowing or browning of leaves
  • premature dropping of leaves, or 
  • the tree being covered in small bumps, which are, in fact, the scales. 

Remedy – The best way to rid your trees of scales is using a horticultural oil spray. This is an insecticide treatment that controls the scales by clogging their breathing pores.


Mites are generally considered insects, but they are not. They are, in fact, part of the arachnid class. They are found on many plants, ranging from trees to indoor plants to bushes. These mites can cause a lot of damage. They harm the greenery by feeding on foliage and stealing necessary nutrients from the plants. They can also carry dangerous diseases, such as rickettsialpox and scrub typhus. 

Signs that your trees are being harmed by these arachnids are quite easy to see. These symptoms can be but are not limited to:

  • speckled foliage
  • brown wilted/yellow curled leaves, or 
  • small web-like structures. 

Remedy – To get rid of these pests, you can use trunk injection pesticide treatment or broad-spectrum insecticide spray.

Boring Insects

Wood-boring insects commonly seek out trees that are already dead or in the process of dying. This does not mean that they will never attack healthy trees. There is a chance that you may find boring insects in your trees. There are many different types of wood-boring insects, and each threatens a different type of tree.

Symptoms that you can see easily include:

  • sawdust-like excrement,or 
  • holes that appear in circular, oval, or simply round shapes. 

While they’re seen easily, they’re seen usually by the time the borers have done their damages. Remedy – You can eliminate the damage done by these pests using a trunk injection pesticide treatment as well.


While one could not completely remove pests such as mites, scales, or boring insects from trees, much can be done to prevent damage the pests cause. It’s important to keep your eye out for signs of any of these insects and arachnids so you can prevent as much damage as possible. Contact a trained arborist to get a professional opinion on what steps to take next.