Yes, caterpillars can defoliate trees and shrubs. In simple terms, this means caterpillars are able to eat all or most of the leaves off a tree or shrub, sometimes leaving the branches bare. This can happen surprisingly quickly, especially if there is a large number of caterpillars present.

What Is Defoliation and Why Does It Matter?

Defoliation is the process where all or most of a plant’s leaves are removed, often by insects, weather events, or diseases. Since leaves are essential for plants to produce food through photosynthesis, losing them can weaken the plant, stop its growth, or even kill it if the damage is very severe or happens repeatedly. When caterpillars feed on the leaves, they disrupt the plant’s ability to make energy, which can slow down growth or make the plant more vulnerable to other stresses.

Which Caterpillars Commonly Cause Defoliation?

Many types of caterpillars are known for eating large amounts of leaves. Some of the most common defoliators include:

• Gypsy moth caterpillars: These can strip entire hardwood forests, affecting oaks, maples, and birches.
• Eastern tent caterpillars: Known for attacking cherry and apple trees, often seen with webby nests in spring.
• Forest tent caterpillars: Affect a wide range of deciduous trees across North America.
• Fall webworms: Feed within webbed nests on a variety of shade and fruit trees.
• Bagworms: Prefer evergreens like junipers and arborvitae but will feed on other plants as well.

Some caterpillars are very host-specific (they only feed on one kind of plant), while others attack many kinds of trees and shrubs.

What Are the Signs of Caterpillar Damage?

• Large, irregular holes or missing sections in leaves.
• Webbing or silk tents on branches or over leaves (common with tent caterpillars and webworms).
• Brown or bare branches where leaves have been eaten away.
• Presence of visible caterpillars, droppings, or shed skins on or under the plant.

A healthy plant can withstand some leaf loss, but repeated or severe defoliations—especially during the growing season—can lead to branch dieback, increased susceptibility to disease and pests, or even death of the plant over time.

What Happens to Trees and Shrubs After Defoliation?

• Most healthy, established trees can regrow their leaves if defoliation happens once in a season. However, they use stored energy to do this, which makes them weaker overall.
• Repeated or severe defoliation greatly increases stress on the plant. When this happens over several years, the tree or shrub may die, especially if it’s already weakened by drought, old age, or disease.
• Young or newly planted trees are at higher risk. Because they have smaller energy reserves, loss of leaves can cause severe damage or death very quickly.
• Defoliated trees are more likely to be attacked by other pests and diseases. For example, bark beetles and fungal diseases often take advantage of stressed plants.

Steps to Shield Your Trees and Shrubs from Caterpillar Damage

• Regularly inspect trees and shrubs in spring and summer when caterpillars are most active.
• Manually remove visible caterpillars, tents, or egg masses if the infestation is small.
• Encourage natural predators like birds and beneficial insects (such as wasps) that feed on caterpillars.
• Use horticultural oils or insecticidal soaps on infested branches, if needed, following all label directions and safety precautions.
• In severe cases or on large trees, consult a certified arborist or tree specialist for safe treatment options.

Can caterpillars defoliate trees and shrubs: Key Takeaways

Caterpillars can and often do defoliate trees and shrubs by consuming most or all of their leaves. This process can weaken or even kill plants if it happens severely or repeatedly. Recognizing the signs early and taking proactive steps can help protect your trees and shrubs from lasting damage.

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