Are you looking for a way to get rid of caterpillars on trees? Here are several ways to keep these larvae away from your trees and garden.
I don’t know about you, but I hate caterpillars. That’s not because I find them gross or something, but because they invade my garden every year and voraciously eat the leaves of many trees and plants in their way.
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- What Are Caterpillars?
- Are Caterpillars Harmful To Plants?
- Are Caterpillars Dangerous To Humans?
- How To Get Rid Of Caterpillars On Trees
What Are Caterpillars?
Caterpillars are the larvae of butterflies and moths. There are more than 20,000 known species living in various regions of the world and some are still unknown.
Many species of caterpillar are considered to be agricultural pests as they can destroy entire crops. Some are only found in tropical climates and are quite rare, while certain common varieties pose a real threat to a wide range of trees and garden plants.
Many people also use the term “webworms” when referring to the species of caterpillars that form silken nests or tents in trees and feed with their foliage. The name “worm” is a bit misleading since these creatures are, in fact, caterpillars, and not really worms.
Caterpillars will typically make their appearance in spring, fall, or even in the summer, depending on the species and the climates they live in. Extended periods of rains may also favorize the occurrence of these pests.
Caterpillars hatch from eggs, and while not all the species build webs, many will establish these enclosures to protect themselves from natural predators.
After they chew all the leaves inside their perimeter, they will then extend the netting more and more. In a large number, they can consume the majority of the leaves of a tree in a short period.
The bad part is that they don’t usually stop there, but will start looking for other sources of food in the nearby. Therefore, traveling from one tree to another until they reach their pupating time (the metamorphosis from larvae to butterfly or moth). The time of the larvae stage usually ranges from 2 to 5 weeks but varies from one species to another.
Because they are not very picky when it comes to their diet, various types of webworms feed with diverse species of plants. Their menu may include hundreds of different species of trees and cultivated plants.
Some of the tree species preferred by webworms include pecans, oak trees, black walnuts, bald cypress, but also various fruit trees like the mulberry trees, quinces, black cherry, plum trees, apple, crabapple, and many more.
While grapevines don’t seem to be the first option on their menu, I’ve seen these caterpillars extending to these types of plants when they are left of other tastier alternatives.
Are Caterpillars Harmful To Plants?
Caterpillars will eventually turn either into butterflies or various species of moths. Could these be harmful to plants?
In the butterfly stage, these critters do not pose a threat to plants. The damage is usually done in their larval phase.
Not all caterpillars are harmful to plants. Or I could better say that some species are more dangerous than others.
For instance, the fall webworm that typically only feeds with leaves produces less damage to plants than the spring-feeding caterpillars that also feed with blossoms and developing fruits.
The young trees are more vulnerable and can suffer irreversible damage if you allow these larvae to chew all their foliage. Additionally, when caterpillars undertake the same tree for more years in a row, that might also lead to undesired effects.
In addition to the damage they cause to the plants, caterpillars quickly spread from one plant to another. Hence, these won’t hesitate to spread to your neighbor’s trees or garden if you do not control them.
Are Caterpillars Dangerous To Humans?
While most species of caterpillars do not represent a direct threat to humans, some rare species possess stinging hairs and venomous spines (e.g., the puss caterpillar, which is one of the most poisonous caterpillars in the US). The poisonous caterpillars can typically be distinguished by their vivid colors, in shades of red, yellow, orange, black, etc.
You should always wear gloves when handling caterpillars, even when you can identify the exact species. Touching the hair on their body can provoke from mild irritation to dermatitis to some persons.
It is also incredibly annoying when you walk under a tree, and you wake up with two or three caterpillars in your hair or when you feel them crawling on your back.
Once they leave their trees and start crawling, they can get inside your house, on porches, basements, or in any other places where you don’t want them.
How To Get Rid Of Caterpillars On Trees
Caterpillars are quite difficult to prevent because butterflies and moths can travel long distances to lay eggs. However, with a few effective control solutions, the number of caterpillars that will emerge next year can be reduced.
Below, I will share a few techniques of getting rid of the caterpillars on trees. While some of these methods may also work in fighting the caterpillars eating other plants, some are only applicable to trees.
If there’s only a reduced number of caterpillars on the leaves of some tree in the fall, I might just ignore them since there’s not too much damage they can do. The leaves of the tree will eventually turn yellow and fall down no matter what.
If I notice them on trees in the spring, I usually try to get rid of them with one or more of the methods below.
1. Bacillus Thuringiensis Pesticide
Do you want to get rid of caterpillars fast? Then you should use a pesticide. However, you shouldn’t use any general-purpose insecticide.
Aren’t pesticides going also to kill the honeybees, ladybugs, and other beneficial insects? No, if you use the right ones.
The best pesticides against caterpillars are the ones that contain Bacillus Thuringiensis (B.t.), a bacteria that naturally resides in the soil and which produces a type of protein that is only toxic for some insect species.
Bacillus Thuringiensis is used as the main ingredient for many insecticides against different types of plant-eating larvae (typically including caterpillars, moths, beetles, black flies, and mosquitoes). This bacteria will start attacking its host at a short time after it is ingested. Caterpillars will stop eating and will typically die a few days after.
This bacteria doesn’t pose a threat to humans and pets. Some B.t. pesticides that do not contain added artificial chemicals are even approved for organic gardening by OMRI.
A pesticide based on Bacillus Thuringiensis bacteria which I use and recommend is Monterey Bacillus Thuringiensis Worm & Caterpillar Killer (click here to order from Amazon).
2. Neem Oil
Neem oil is a very efficient natural insecticide that has no harmful effects on humans or plants. The cold-pressed neem oil is widely used to control many garden pests, including aphids, caterpillars, Japanese beetles, spider mites, and more.
I use the following recipe:
- 1 gallon of water
- 2 tablespoon of natural cold-pressed neem oil
- 1 teaspoon of organic liquid dish soap
The main ingredient is the neem oil, but you cannot use it undiluted. The dish soap will act as an emulsifier and help the neem oil mix with the water.
Even though the neem oil itself shouldn’t have any side effects on plants, it’s better to test the solution first on a few leaves before you spray the entire caterpillar infested areas.
Wait about 24 hours to make sure that the resulting concentration doesn’t harm the foliage. Some tree species can respond differently to the same mixture.
If you cannot see any changes on the leaves, spray the solution with a pulverizer directly on the caterpillars’ infested area. Do not sprinkle the whole tree with it. The neem oil will also kill beneficial insects like bees or ladybugs.
You should start seeing the effects of neem oil almost instantly. Caterpillars sprayed with this natural pesticide will die soon after.
Repeat this neem oil treatment after 7 to 14 days if necessary.
3. Pick Them Up
I’m sure that many of you didn’t want to hear this.
Many persons find the caterpillars gross, or they are afraid to handle them. However, that’s one of the most efficient ways to get rid of caterpillars in their early stages and in a very nature-friendly manner.
If you act fast, before they spread to the whole tree, you can collect the webworms manually. Just prune the small tips of the affected branches and take the caterpillars along with their webs.
Gather them in a bucket and either exterminate or release them far away from your property (and someone else’s).
Don’t forget to always wear gloves when you collect caterpillars.
If you are dealing with a large number of these pests or if the infestation is already in an advanced stage, picking them up may not be the best solution.
4. Garlic & Hot Peppers Insecticide
You can prepare an environmental-friendly organic caterpillar repellent solution with the help of garlic and hot peppers.
Unlike the neem oil pesticide solution, which kills the caterpillars, this composition made of garlic and hot peppers, is intended more for prevention. Consequently, this solution creates an undesirable medium for webworms and other insects.
This mixture may be effective for small affected areas. However, since it doesn’t kill the caterpillars, these pests might just move to other nearby trees.
- 1 gallon of water
- 6-7 garlic cloves (or more for a higher concentration)
- 1 tablespoon of crushed hot pepper
- 1 tablespoon vegetable oil
- 1 teaspoon of organic liquid dish soap
You can even add grated horseradish or other plants with a repellent smell and powerful taste.
Mix everything together and pulverize the solution on the foliage of the tree or other plants to repel caterpillars and other pests.
Note that this mixture will lose its properties if not utilized shortly after the preparation. You can keep it in the freeze for a few days, but not more.
5. Caterpillar Repellent Plants
Another method of preventing a caterpillar infestation is by growing in the nearby plants that are natural repellents of insects and other pests.
Below is a list of a few plants that repel caterpillars and other common garden pests:
This approach might work best for protecting young trees, but it’s usually more effective for small plant ground crops. These aromatic plants also won’t kill any existing pests, so it may not be the most suitable solution to a caterpillar problem.
6. Caterpillars Natural Predators
Sometimes, when you are facing garden pests, it is best to let nature follow its course. Or, when necessary, you can help it a little.
Just as the majority of insects, caterpillars have several natural enemies.
Certain species of birds can come to your aid, such as scarlet tanagers, rose-breasted grosbeaks, warblers, and several other small birds. You can attract more wild birds to your garden by placing a few bird feeders in the trees.
For plants that grow close to the ground, even chickens and ducks can help.
Even though birds are probably the largest caterpillar consumers, there are also other types of insects that love to feed with these larvae. Among these, it’s worth mentioning the ladybugs (ladybird beetles) and wasps (yellow jackets).
Frogs and lizards also like to include caterpillars in their diet. Again, these might give you a hand with the on-ground crops, but won’t be very helpful when it comes to getting rid of the caterpillars on trees.
7. Slippery Duct Tape
An ingenious way to keep caterpillars, ants, and other wingless pests from crawling back to a tree is to cover the tree trunk with one or two duct tape wraps. This approach won’t kill any existing caterpillars nor drive them away from an already infested tree.
The science behind this caterpillar prevention method is that the larvae tend to move from one tree to another when they run out of leaves to chew. Once on the ground, they will try to climb on any new tree. However, if the tree’s trunk is wrapped with duct tape, the larvae will slip down; hence, they won’t be able to reach the foliage.
Any duct tape with a slippery surface should work. However, it is advisable that you find one that has a strong glue and is resistant to different climatic conditions, such as rain, UV, and high temperatures.
There are also products like Tanglefoot Tree Care Kit & Insect Barrier (check it on Amazon), which works based on a similar concept, except for the fact that instead of using a slippery surface, this tree pest repellent uses a strong glue to trap the insects.
Regardless of the product you choose, keep in mind though that this is only a prevention method. Therefore, if you apply it to a tree that’s was already occupied by caterpillars, you’ll have to first clean the tree out of the existing pests.
Getting rid of caterpillars on trees is oftentimes pretty challenging. These pests not only make their shelters high in the trees, but many species also produce networks of webs meant to protect them from climate conditions and natural predators.
While not all species produce webs, some types can build dense protective cells, like the tent caterpillars.
If you are dealing with a species that make these webs, it’s advisable to destroy these enclosures using a pole, compressed air, or a strong water jet before you apply any insecticide.
If allowed, caterpillars spread quickly from one plant to another. They also tend to come back year after year, which makes the task even more difficult.
Do you know additional ways to get rid of caterpillars on trees? Leave a comment below.