These 5 Pests Will Damage Your Trees

July 31, 2024

Photo by Pongsatorn Suwannapa

How to Combat These 5 Pests That Damage Your Trees

It can be difficult to tell at first glance if the insects you are dealing with are pests that can do irreversible damage to your trees. A lot of pests just look like harmless small bugs, and there are so many to keep track of—how do you stay aware of the bugs that have the potential to kill your trees?

We are going to give you a rundown of some of the top pests that cause tree damage in the United States and how to combat them when you find them on your trees.

Fall Webworm

Fall webworms in Rentschler Forest, Fairfield, OH. Andrew C./Wikimedia Commons

First on our list is the fall webworm. This pest is a moth from the family Erebidae , and it is mostly known for its larval stage. This is when it creates elaborate webbed nests on the limbs of different hardwood trees in the late summer and early fall.

This pest is well known to arboriculturists and tree services because it is incredibly damaging to the tree’s aesthetics. The heavy, thick webs that the fall webworm creates are ugly to look at and tedious and painful to remove. Luckily, it is believed that the issues they cause are mostly to how the tree looks, and they aren’t believed to hurt trees that are otherwise healthy.

The fall webworm is actually native to North America and spans the entire country from Mexico to Canada.

Fall webworms are able to create enormous, detailed webs on many, different types of host plants, and the webs can be many different shapes and at many elevations as well. They also spread incredibly quickly, making them pretty difficult to control once they take over an area of trees. They also tend to make their webs and defoliate plants in areas that humans populate regularly, such as parks and other recreational areas.

So what do you do about this pest? There are several different methods for handling the insects and getting rid of them.

You are able to simply use a long stick or rake to pull down the webs and kill the fall webworms by hand. This is the most straightforward way to go about it, but there are other options if you are squeamish or uncomfortable doing so.

If you would prefer to let the natural world handle this problem, all you have to do is tear a hole in the nest and allow their natural predators to come for them. Birds, wasps, and yellow jackets are all wildlife that would happily eat the pests. You can even plant flowers or plants that their predators like around the nests, and they will take care of the whole process for you.

You most likely won’t have to use any insecticides for this process unless it is a pretty extreme case. If you do have such a problem that you need to use one, simply spray it over the nest lightly, and the pests will come in contact with it.

Forest Tent Caterpillar

A Lone Forest Tent Caterpillar - Mhalcrow/Wikipedia Commons

The next pest we have on our list is the forest tent caterpillar moth. This is a moth from North America that is found throughout the United States and Canada, mostly in the eastern parts of the countries. These pests weave a sheet that is silky, and they lay on it together while they molt. They also create silk trails to move easily over branches and to be able to travel in groups—they’re very social insects.

The forest tent caterpillar moths prefer oak, sweetgum, aspen, sugar maple, and tupelo trees to lay their eggs on in the summer. The eggs are laid in masses of up to three hundred and are covered in an incredibly sticky substance called spumaline—this goo stops them from freezing or being easily destroyed.

Every decade or so, there are high population density outbreaks that occur and last from two to three years. During this time, the trees that they take over are almost completely denuded of leaves. After that time frame, most of the plants are able to replace the lost leaves and avoid permanent damage.

There are a few options for getting rid of these pests as well.

You can scrape the egg masses off and discard them and tear the protective tents out by hand before the larvae begin feeding.

If you don’t want to handle any of that by hand, there are a few products that will be helpful as well. You can use AzaMax, which contains azadirachtin—this is a key insecticidal ingredient that is found in neem oil. The product will disrupt the growth and development of pest insects and also has repellent and antifeedant properties. It is also nontoxic to many beneficial insects, including honey bees.

Your very last resort should be botanical insecticides. However, if you do end up needing to use one, using a natural pesticide will have fewer harmful side effects than using those made of synthetic chemicals, and it will be able to break down more quickly in the natural environment.

Nantucket Pine Tip Moth

A Close-up of a Nantucket Pine Tip Moth - Wikimedia Commons

The Nantucket pine tip moth, also known as Rhyacionia frustrana , is a moth from the Tortricidae family. It is found sporadically throughout the United States—the pest resides anywhere from Massachusetts down to Florida and west to Oklahoma, Missouri, Texas, and California. It can also be found in Cuba, Jamaica, Mexico, Honduras, Guatemala, Nicaragua, and the Dominican Republic.

The larvae of this pest actually feed on various different pine species, including Pinus caribaea, Pinus banksiana, Pinus cubensis, Pinus contorta, Pinus rigida, Pinus ponderosa, Pinus virginiana, and many more. This insect is considered to be a very serious pest of young pines in plantations, Christmas tree plantings, ornamental pines, wild pine seedlings that thrive in open areas, and pine seed orchards.

The young larvae will feed on the outside of the newly growing seedling for a short period of time and then, later on, will bore into the shoot tips, conelets, and buds. Then pupation occurs in damaged tissues.

They end up causing quite a bit of damage with these actions. After they bore into the seedlings, it ends up causing bud and shoot mortality, resulting in tree deformation, reduced diameter and height growth, and even tree mortality if it is a serious enough case.

Unfortunately, with Nantucket pine tip moths, you are most likely going to have to chemically exterminate them to get rid of them completely. Using an insecticide has been found to be the most efficient and thorough way to remove them from your trees.

Balsam Wooly Adelgid

Balsam Woody Adelgids Infesting a Branch - Photo from Wikimedia Commons

The next pest on our list is the balsam wooly adelgid. These are small insects without wings that infest and kill firs—they specifically go after the Fraser fir and balsam fir.

The biggest issue with this particular insect is that it originated in Europe and was introduced to the United States around the year 1900. This means that the Fraser fir has not evolved to have any type of natural defense against this pest because it is not native to the U.S.

These insects will usually lay around one hundred eggs and will have about three generations per year. They attack the trees by feeding in fissures within the bark of trees. As they feed, they release toxins that are contained in their saliva, which reduces the conductance of sapwood being built. This causes water stress and the inevitable death of the trees affected.

If you are looking for these on your own trees, they will appear as small white dots spreading across the trunks of the trees.

This is another pest that has such extensive damage potential that swift chemical extermination is the best method of getting rid of it.

Aphids

Ants Feeding on Aphid Honeydew - Photo from Wikimedia Commons

Last on our list are aphids. These are very tiny, sap-sucking insects, and they are members of the superfamily Aphidoidea. They are more commonly known as greenfly or blackfly, but they can vary widely in color.

These pests are some of the most destructive insects for cultivated plants in temperate regions. On top of sucking the sap out of the plants and weakening them, they also act as vectors for different plant viruses and destroy ornamental plants by depositing honeydew and sooty molds.

Aphids are also difficult to stop because they rapidly multiply by asexual reproduction.

There are a few different methods for getting rid of these insects. You can use soap sprays and water jets, which is fairly easy and very effective for removing them completely. They also have quite a few natural enemies, including parasitic wasps, ladybugs, crab spiders, lacewing larvae, etc.