7 Ways To Get Rid of Silkworms (Tent Caterpillars) For Good

Eastern tent caterpillars inside and outside of silky nest. Caterpillar (malacosoma americanum) is a species of moth,

Have you ever noticed those big ugly webs in tree forks or at the end of tree branches? These untimely natural Halloween decorations appear in spring and tent worms, often referred to as silkworms, are the cause. If these nuisance caterpillars affect your trees, you will be happy to know there are ways to get rid of them for good!

Silkworm is the term given to tent worms, which are actually caterpillars. You can remove these pesky caterpillars from your trees with several methods. You can handpick the caterpillars off with gloves if the numbers are small, destroy the egg mass, remove the tent, or prune the affected branches.

Below we will go over all the ways you can get rid of silkworms (tent worms) and keep them away for good. We will also talk about some background on tent caterpillars, so you know exactly what you are dealing with. Let’s get to it!

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Are Silkworms And Tent Worms The Same Thing?

You have probably heard these web-making worms referred to as either tent worms or silkworms, or maybe both! 

However, silkworms and tent worms are two very different insects. And just to add to the confusion, neither of them are worms either. They are both caterpillars, which eventually cocoon and then turn into moths.

Both silkworms and tent worms belong to the same order, Lepidoptera, but their similarities end there in the eyes of geneticists. 

So how are these two creepy crawlers different from each other?

Silkworm Vs. Tent Worm Silk Use

Both caterpillars can produce silk, but they use it in different ways. The caterpillar releases silk from its head through a specialized organ known as a spinneret.

Silkworms use their silk to build a cocoon that protects them as they morph from caterpillar to moth. The domesticated silkworm is an incredibly important insect in the textile industry, as they are the major producers of silk for fabrics.

Tent worms use their silk to build webby tents that serve as their protective homes while in the caterpillar stage. Tent worms also spin their cocoons with silk before morphing into their adult moth stage.

Silkworm Vs. Tent Worm Harm To Trees

One of the biggest differences between silkworms and tent worms is their status with humans. One is a pest, the other is so important it has been domesticated and farmed, just like cattle or sheep.

We consider tent worms pests because of the unsightly webs they build in trees. The caterpillars also chow down on leaves while fattening up for their cocoon stage, causing defoliation. When gathered in large numbers, tent worms can cause some serious damage to trees, albeit typically not fatal to the tree.

Silkworms are our friends! There are both wild and domesticated silkworms. Domesticated silkworms are an enormous source of silk in the textile industry. Wild silkworms are sometimes used to produce silk, but not as much as the domestic silkworm.

Even if they did not produce silk and help the textile industry, these moths only eat white mulberry leaves (they don’t eat oak tree leaves), so they do minimal damage to the environment.

Silkworm Vs. Tent Worm Physical Appearance

Silkworms and tent worms differ in both color and size. 

The domesticated silkworm has been genetically modified to be larger than their wild cousins. They rapidly reach 3 inches in length while feeding constantly in the caterpillar stage. They are mostly white or cream-colored.

Tent worms are slightly smaller, reaching anywhere from 2 to 2½  inches in length, according to the University of Kentucky. They are black with a distinct white stripe down their back. Along their sides are brown and yellow racing stripes dotted with blue spots.

Silkworm Vs. Tent Worm Native Range

The domesticated silkworm is no longer found in the wild, but their cousins, the wild silkworm, can still be found outdoors.

Wild silkworms are found in India, China, Korea, Japan, and Russia. There are silk moths found in North America, but these are not from the same family as the domestic silk moth.

There are over 20 species of tent worms, but only 6 are native to North America. Among the six species, they cover most of the United States, with each caterpillar occupying a slightly different range.

Why Should You Get Rid Of Tent Worms?

Forest tent caterpillar in wisconsin

Now that we have established silkworms = good and tent worms = bad, let’s go over why you want to get rid of tent worms.

In the long run, tent worms will most likely not kill your trees. They might defoliate your tree, even causing it to go bald in the middle of summer. But your tree will recover and put out a fresh crop of leaves before the year is over.

That does not mean tent worms are doing your trees any good, though…

Tent Worms Cause Defoliation

There is nothing better than coming home from a long day’s work, sitting on your porch, and enjoying your yard. The trees, the flowers, the little critters running around.

So, when you look out on your oasis and see your trees are bald in the middle of summer, it can be soul-crushing.

Tent worms are voracious eaters. And they are not picky, either! Because tent worms live across the whole U.S., they eat whatever is local to the area, according to a 2017 study.

In the west, this means quaking aspen, willows, and birch trees. Eastern tent worms like maples, oaks, and elms. In the south, tent worms will target gum trees, live oaks, and water tupelo.

Defoliation is worse in the spring. The eggs of tent worms will hatch around March, and they will feed and feed and feed for about 6 weeks until they are full-grown, hairy caterpillars.

Even though your tree will recover from defoliation, if the tent caterpillar population is too big and they eat too many leaves, it can stunt the growth of your trees.

Tent Worm Webs Take Over Trees

Tent worms eat the heck out of leaves, but your tree will recover and sprout new leaves either later that year or the following spring.

However, something that your trees cannot get rid of on their own is the tent webs these caterpillars get their name from. These tents pop up in the spring after the caterpillars hatch from their eggs.

The tents may start small, but tent worms are social caterpillars if you can believe it! They will invite in friends and family, long-distant cousins and aunts until there are hundreds of caterpillars in a single tent.

As the caterpillars grow, so does their tent. Trees have no way of getting rid of these tents naturally, and the strength of the silk means the webs can stay in the tree long after the caterpillars have moved out.

While these webs do not do any actual damage to the tree, they can be unsightly to see and will give your backyard oasis a sinister look.

How To Get Rid of Tent Worms For Good

Tent worms are more of a nuisance than a danger to your trees, but we still do not want them building unsightly webs in our trees, right?!

Let’s go over some ways you can get rid of these web-building caterpillars for good, and keep them away.

If you’re finding that you have another type of caterpillar on your tree, read our guide on removing caterpillars from your tree here.

Insects with white silk nests built on shrub.

Pick Tent Worms Off Trees

The first option on our list is not for everyone, and it is definitely situational. This option is best used in situations where the caterpillars have already hatched, eaten their fill, and are wandering around looking for a place to cocoon.

During this time, tent caterpillars will leave their tents and go searching for a place to cocoon. If webbing or defoliation did not affect your tree, it may still be in danger from these wandering caterpillars.

They will cocoon on your tree, grow into a moth, and lay eggs on the same tree for the next generation of caterpillars to hatch the following spring.

If you notice them on your tree, you can put on some gloves and pick them off individually before they decide to make your tree their home.

Prune Affected Branches To Remove Tent Worm Eggs

You can use pruning at both the egg stage and the tent stage. The easiest way to use pruning is during the egg stage. 

So, bust out your trusted pruning shears, or buy some like the Gonicc 8” Pruning Shears, made of high carbon steel, so they will cut right through small branches.

Winter is the best time to look for tent worm eggs, as all the leaves of their favorite deciduous trees will be off, giving you a clear view of the branches and twigs.

Look for twigs that are about as thick as pencils. Egg masses will be black and look a slightly shiny, enveloping part of the twig. Prune these twigs off your trees to keep the eggs from hatching and chowing down on your favorite backyard shade suppliers.

If you did not catch the egg masses in the winter, there is always spring! After these caterpillars hatch, they will almost immediately begin feeding and building their tent. If you see these tents in your trees, you can simply prune those branches off to get rid of the tents.

Physically Remove Tent Worm Webs

If you do not want to cut any branches off your tree, you can use other methods to remove those unsightly web tents.

You can take any sturdy stick-like tool (think broom handle, shovel handle, or a sturdy dropped branch) and poke it into the tent. Swirl the stick around to wrap the tent around the pole/stick. The sticky webbing material should grab onto your stick pretty easily.

This method is a good way to remove the tent quickly without having to put too much work into it. The tent-building stage only lasts for about 6 weeks, so if you take a tent down and do not see any more being built, you are probably safe for the season.

Use A Targeted Tent Worm Insecticide

Regular old insecticides are not recommended for getting rid of tent worms. They can affect non-target species such as natural predators of tent worms. Instead, you will want to use something that is more targeted toward these caterpillars.

Bacillus thuringiensis, also known as BT, is an insecticide that works specifically on caterpillars. Monterey BT Worm & Caterpillar Insecticide is a concentrated product you mix with water before using.

When used as directed, BT does not affect birds, bees, ladybugs, or other beneficial insects. And despite having the name ‘worm’ in the product name, it does not affect earthworms, either, which are very beneficial for your garden.

Encourage Tent Worm Predators To The Area

Tent caterpillars are pretty low on the food chain. There are plenty of things out there that view them as a tasty meal or snack. You can use this to your advantage to keep their population under control.

The dominant predators of tent worms are parasitic wasps, but it is difficult to attract these tiny parasites. However, birds and lizards also feed on tent worms, and these are much easier to attract.

If you want to encourage birds to come around, try hanging a bird feeder from trees where you see tents. Even better, hang bird feeders out before you notice tents to prevent these caterpillars from moving into your tree.

All of your average birds will eat tent caterpillars – blue jays, cardinals, robins. Pretty much any songbird. You can use a simple bird feeder like Funpeny Hanging Wild Bird Feeder and fill it with multiple types of seed to attract a variety of songbirds.

Change Your Outdoor Lighting To Repel Tent Worms

We have talked about stopping these web-building caterpillars at both the egg stage and the caterpillar stage. Now, let’s move on to the moth stage.

Usually, around June or July is when tent caterpillars will emerge from their chrysalis as adult moths. The moths are brownish to yellowish and have diagonal markings on each wing. All in all, these little moths are about one inch from wingtip to wingtip.

We all know light attracts moths. This universal fact can be used to our advantage by using different colored floodlights that are less attractive to moths.

Bluex Bulbs Amber Yellow LED Bug Light can easily replace your outdoor porch light or floodlight. These bulbs give off an amber-yellow light instead of the normal white light. Yellow and amber light is far less attractive to moths and other nighttime flyers.

This is more of a preventative measure that will help you the following year. The less attractive your yard is to moths, the less likely they are to lay eggs in nearby trees.

What Attracts Tent Caterpillars?

The forest tent caterpillar - the major pest in hardwood stands

Is there something you can do to stop tent caterpillars from coming to your yard? What exactly is the reason they are here?

Tent caterpillars are most attracted to suitable trees and cocoon weaving areas. Deciduous trees are attractive to tent caterpillars, who munch on the leaves for food and use the branches to build webs.

Besides this obvious attractant, tent caterpillars love fragmented forests. Forests with lots of edges and separation will be the most affected by these web-building caterpillars. So, suburban areas, agricultural areas, or small parks with fragmented trees will be where these caterpillars thrive the most.

A study found fragmented forests are the number one indicator of large outbreaks of tent worms. The reason? Parasitoid wasps and pathogens that affect tent worm populations the most are less present in these areas.

Agriculture, logging, and general deforestation are increasing the outbreaks of tent caterpillars by creating these forest edgings and fragmentations.

The weather seems to have little impact on tent caterpillars. However, a study done in Ontario observed that there was decreased defoliation when overwintering temperatures were super cold (below -40°F).

How Long Do Tent Caterpillars Last?

If you have seen tents popping up here and there, you might wonder how long you have to be on guard and ready with your broomstick?

Luckily, the lifecycle of a tent caterpillar is pretty short. You can expect tents to form around March to April after the eggs hatch. The caterpillars will stick around until they are ready to spin their cocoons, usually at the end of May or the beginning of June.

At this time, they will leave their webs behind and find a spot to spin their cocoon. Once cocooned, it takes around 3 weeks until the adult moth emerges from the chrysalis.

Unfortunately, the webs can remain in the trees long after the caterpillars have moved on to their moth stage. The only way these webs get destroyed naturally is by inclement weather like rain, snow, and wind. 

If you are not willing to wait, you may have to destroy the webs yourself. 

Wrapping Things Up

Now that you are thoroughly wrapped up in a cocoon of tent caterpillar knowledge, you will be able to combat these web-slingers in the springtime!

To recap, the 7 ways to get rid of tent caterpillars indefinitely include:

  • Picking off individually (Early Summer)
  • Destroy egg masses by pruning affected branches (Winter)
  • Destroy web tents by pruning affected branches (Spring)
  • Use tool to remove webs (Spring)
  • Use BT-based insecticides to target caterpillars specifically
  • Encourage predators (put out a bird feeder)
  • Use yellow or amber lighting outdoors to discourage tent worm moths

Although we often call silkworms and tent worms the same thing, they are two very different insects. Tent worms are the ones you want to look out for, while silkworms are harmless and only target mulberry leaves.

References

Daniel, C. J., & Myers, J. H. (1995, December). Climate and outbreaks of the forest tent caterpillar. Ecography, 18(4), 353-362. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0587.1995.tb00138.x

Parry, D., Spence, J., & Volney, W. (2003, October 30). Responses of natural enemies to experimentally increased populations of the forest tent caterpillar. Ecological Entomology, 22(1), 97-108. https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2311.1997.00022.x

Roland, J. (1993). Large-scale forest fragmentation increases the duration of tent caterpillar outbreak. Oecologia, 93, 25-30. https://link.springer.com/article/10.1007/BF00321186

Schowalter, T. D. (2017, January). Biology and Management of the Forest Tent Caterpillar (Lepidoptera: Lasiocampidae). Journal of Integrated Pest Management, 8(1), 24. https://academic.oup.com/jipm/article/8/1/24/4157677?login=true

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