Tent worms, also known as tent caterpillars, are common pests that can cause significant damage to trees and shrubs by defoliating them. These caterpillars are named for the large silk webs, or “tents,” they create in the branches of trees. While their presence is often more of a cosmetic issue, large infestations can weaken trees, making them more susceptible to other pests and diseases. In this guide, we’ll explore effective methods for identifying, managing, and eliminating tent worms from your landscape.
What Are Tent Worms?
1. Understanding Tent Caterpillars
Tent worms are the larvae of moths from the Malacosoma genus, and they commonly infest deciduous trees, such as cherry, apple, and maple trees. These pests create silk tents in the forks of branches, where they shelter during the day and emerge at night to feed on leaves.
There are a few types of tent worms to be aware of:
- Eastern Tent Caterpillar (Malacosoma americanum): Commonly found in North America, they build tents in the forks of tree branches and primarily infest fruit trees like cherries, apples, and crabapples.
- Forest Tent Caterpillar (Malacosoma disstria): Unlike eastern tent caterpillars, forest tent caterpillars don’t create silk tents but still travel in groups, leaving a similar defoliation pattern.
- Western Tent Caterpillar (Malacosoma californicum): Found in western parts of North America, these caterpillars behave similarly to their eastern counterparts.
2. Signs of Tent Worm Infestation
- Silk Tents: The most obvious sign of an infestation is the presence of large silk tents or webs in the forks of tree branches.
- Defoliation: Tent worms can strip the leaves off branches, leaving them bare and causing a thinning canopy.
- Caterpillars: If you see large groups of caterpillars on your trees, especially in late spring or early summer, it’s likely tent worms.
- Frass: As they feed, tent caterpillars leave behind small black droppings called frass, which may accumulate on the ground beneath the tree.
Tools and Materials Needed
Before beginning the removal process, gather the necessary tools and supplies to ensure safe and effective tent worm control.
1. Tools
- Pruning Shears: For cutting out infested branches or directly removing silk tents.
- Garden Hose: To dislodge tents and caterpillars from trees using a high-pressure spray.
- Ladder: If you need to reach high branches.
2. Supplies
- Insecticidal Soap: A safe and effective treatment for caterpillars on trees.
- Bacillus thuringiensis (Bt): A biological insecticide that targets caterpillars without harming beneficial insects or wildlife.
- Horticultural Oil: Used to suffocate eggs or caterpillars during the dormant season.
- Sticky Tree Bands: These prevent caterpillars from climbing the tree and reaching foliage.
- Gloves: For handling tree branches and pests safely.
- Trash Bags: To dispose of infested branches and caterpillars.
Step-by-Step Methods for Getting Rid of Tent Worms
1. Manual Removal of Tent Worms
The simplest and most immediate way to control tent worms is by manually removing their silk tents and caterpillars.
How to Remove Tent Worms by Hand:
- Locate the Silk Tents: Tent worms build their silk nests in the forks of tree branches. Inspect your trees, particularly in the early morning or late afternoon, when the caterpillars are inside the tent.
- Cut the Tent from the Tree: Use pruning shears or scissors to carefully cut the tents from the tree. If possible, do this early in the morning or evening when the caterpillars are inside the tent.
- Destroy the Tents and Caterpillars: After removing the tents, place them in a trash bag and seal it tightly. You can either dispose of the bag or crush the caterpillars inside to ensure they don’t return to the tree.
- Hose Down the Tree: Use a strong stream of water from your garden hose to blast any remaining caterpillars off the tree. This will also help break apart any silk that remains attached to the branches.
Pros of Manual Removal:
- Environmentally friendly.
- Effective for small infestations.
- No chemicals needed.
Cons of Manual Removal:
- Time-consuming, especially with larger infestations.
- May require a ladder to reach higher branches.
2. Using Insecticidal Soap or Natural Remedies
Insecticidal soap and other natural remedies are safe, non-toxic options for eliminating tent worms, particularly for those looking for eco-friendly solutions.
How to Use Insecticidal Soap:
- Choose an Insecticidal Soap: Select a product specifically formulated for use against caterpillars and other soft-bodied pests. Ensure it is labeled for use on trees and shrubs.
- Apply the Soap Directly to the Caterpillars: Spray the solution directly onto the caterpillars, focusing on areas where they congregate and feed. The soap will suffocate the pests by disrupting their cell membranes.
- Repeat as Necessary: You may need to reapply the insecticidal soap over the course of several days to completely eliminate the tent worms.
Alternative Natural Remedies:
- Vinegar and Dish Soap Spray: Mix one part vinegar and one part water, then add a few drops of dish soap. Spray this mixture directly on the caterpillars and their tents to kill them.
- Neem Oil: Neem oil is another natural remedy that can kill caterpillars by disrupting their feeding habits. Apply neem oil according to the manufacturer’s instructions.
Pros of Natural Remedies:
- Safe for pets, children, and beneficial insects.
- Effective for mild to moderate infestations.
Cons of Natural Remedies:
- May require multiple applications.
- Not as effective for large infestations.
3. Using Bacillus thuringiensis (Bt)
Bacillus thuringiensis (Bt) is a naturally occurring bacteria that specifically targets caterpillars without harming other wildlife or plants. It’s one of the most effective biological controls for tent worms.
How to Use Bt for Tent Worms:
- Choose the Right Bt Product: Look for a product labeled for use against caterpillars, such as Bt kurstaki (Btk), which specifically targets moth larvae.
- Apply Bt to the Affected Tree: Use a spray bottle or garden sprayer to apply Bt to the foliage and directly onto the tent caterpillars. Focus on areas where the caterpillars are actively feeding.
- Wait for Results: Bt works by damaging the caterpillar’s digestive system, causing them to stop feeding and die within a few days. Monitor the tree for continued activity and reapply if necessary.
Pros of Using Bt:
- Safe for the environment and non-toxic to humans, pets, and beneficial insects.
- Effective for large infestations.
Cons of Using Bt:
- Takes a few days to kill caterpillars, so it’s not an instant solution.
- Requires careful application to ensure contact with the caterpillars.
4. Horticultural Oils for Tent Worm Control
Horticultural oils can be used during the dormant season (late winter or early spring) to smother overwintering egg masses, reducing future tent worm populations.
How to Apply Horticultural Oils:
- Apply During Dormant Season: Dormant oils are best applied when the tree is not actively growing. This will help suffocate tent worm eggs before they have a chance to hatch in the spring.
- Coat Branches and Twigs: Spray the oil evenly over the branches and twigs, ensuring that the entire surface is covered. Pay special attention to areas where you’ve seen egg masses or where caterpillars have previously nested.
- Repeat Annually: For ongoing protection, apply horticultural oils each dormant season to keep tent worms at bay.
Pros of Horticultural Oils:
- Prevents tent worm outbreaks before they start.
- Safe for most trees and non-toxic to humans and pets.
Cons of Horticultural Oils:
- Must be applied during the dormant season for effectiveness.
- Will not kill active caterpillars.
5. Preventing Tent Worms with Sticky Tree Bands
Sticky tree bands can be placed around the trunks of trees to prevent tent caterpillars from climbing up to reach the foliage. This method is especially useful for preventing infestations in the first place.
How to Install Sticky Tree Bands:
- Wrap the Tree with a Band: Place a sticky band around the tree trunk at chest height. Make sure the band is snug but not tight enough to damage the bark.
- Check the Bands Regularly: The sticky surface will trap caterpillars as they try to climb the tree. Check the bands every few days, and replace them when they become covered with debris or caterpillars.
Pros of Sticky Tree Bands:
- Prevents caterpillars from reaching tree branches.
- Non-toxic and chemical-free.
Cons of Sticky Tree Bands:
- Only effective for preventing caterpillars from climbing the tree, not for eliminating those already present.
Preventing Future Tent Worm Infestations
Once you’ve eliminated tent worms, take the following steps to prevent future infestations:
1. Regular Monitoring
Inspect your trees regularly, especially in early spring when tent worms first become active. Look for signs of egg masses or newly formed silk tents, and take action early to prevent the caterpillars from spreading.
2. Remove Egg Masses
Tent worms lay their eggs in dark, shiny masses around tree branches. These eggs overwinter and hatch in the spring. If you spot egg masses during the winter or early spring, scrape them off the branches and dispose of them to prevent a new infestation.
3. Encourage Natural Predators
Birds, especially black-capped chickadees, love to eat tent worms. Encouraging birds in your garden by providing bird feeders or nesting boxes can help naturally control tent worm populations.
Conclusion
Tent worms can be a nuisance, but with the right approach, they can be effectively controlled and prevented from causing lasting damage to your trees. Whether you opt for manual removal, natural treatments, or biological controls like Bt, taking action early is key to managing tent worms. With regular monitoring and proactive measures, you can keep your trees healthy and free of these destructive pests.