Fall Webworms

Identification

Size: Webworm caterpillars are usually about one inch in length when fully grown

Color: The colour typically varies from a light, creamy colour to a slightly green or yellow tint

Description: Webworms, commonly referred to as fall webworms, are a pest species native to North America and parts of Asia that primarily target hardwood trees. The caterpillar stage, which causes the most damage, is typically one inch in length and varies in colour from a light creamy hue to a slightly green or yellow tint. As adults, they transform into moths with a wingspan of approximately 1 to 1.5 inches, usually white or pale with small dark spots on their wings. These creatures are known for building extensive silk webbing nests on trees, hence their name “webworms.”

Webworms, also known as fall webworms, are the caterpillar stage of a species of moth (Hyphantria cunea). They are known for creating large, conspicuous webs in trees, and they feed on the leaves inside these webs. The caterpillars have a wide range of potential coloration, but most commonly, they are a pale yellow or green colour with long, fine hairs.

Webworms are considered pests because they can defoliate trees, particularly hardwood species. They are widespread in North America and parts of Asia and have been introduced to other regions as well.

The adult form of the webworm is a white or pale moth with small dark spots on its wings. It has a wingspan of around 1 to 1.5 inches. Despite the damage they can cause as caterpillars, the adult moths do not pose a significant threat to trees.

Webworm infestations can be managed with various methods, including biological controls such as natural predators and parasites, as well as chemical insecticides if necessary. However, in most cases, the trees can survive a webworm infestation, even if they are defoliated, and will produce new leaves the following year.

Webworms, also known as fall webworms, are identifiable through several unique signs. The most prominent indication is the presence of large, silken webs enclosing branches and leaves of trees. Inside these webs, you might spot the caterpillars themselves; they’re typically about an inch long and display a range of colors from light, creamy hues to green or yellow tints, all covered in fine hairs. Damaged or missing foliage within these webs is also a strong sign of a webworm infestation.

The adult form of a webworm is a moth, which is generally white or pale with small dark spots on their wings and a wingspan of about 1 to 1.5 inches. Seeing these moths is often a hint of webworms in the caterpillar stage nearby. Webworms commonly infest tree species such as pecan, walnut, American elm, hickory, and various fruit trees. Despite the aesthetic damage caused by webworms, most healthy trees can recover from an infestation and regrow leaves in the following season.

Webworms, or fall webworms, are quite noticeable due to their distinctive behaviours and characteristics. Here are some signs that you may have a webworm infestation:

Presence of Silken Webs: Webworms are notorious for creating large, conspicuous silken webs that encompass branches and leaves of trees. If you observe these types of webs in your trees, it’s likely that you have webworms.
Visible Caterpillars: Inside these webs, you might see the caterpillars themselves. They are typically an inch long when fully grown and vary in color from a light, creamy hue to a slightly green or yellow tint.
Chewed or Missing Leaves: One of the key signs of a webworm infestation is noticeable defoliation. The caterpillars feed on the leaves inside their protective webs. If you see leaves that are chewed up or missing entirely, especially within a silken web, webworms may be present.
Adult Moths: Adult webworms are moths that are generally white or pale with small dark spots on their wings. If you’re spotting these moths around your trees, it’s possible that webworm caterpillars are nearby.
Preference for Certain Trees: Webworms tend to target certain tree species, including pecan, walnut, American elm, hickory, and various fruit trees. If these trees show signs of infestation, webworms could be the culprit.

It’s important to remember that while webworms can cause significant defoliation, most healthy trees are resilient enough to survive an infestation and will regrow leaves in the following season. If you suspect a webworm infestation, you might want to consult with a local arborist or extension service for advice on how to manage it.

Preventing a webworm infestation, like any pest issue, largely depends on proactive monitoring and maintenance of your trees. Here are some strategies to prevent a webworm infestation:

Regular Monitoring: Regularly inspect your trees for the early signs of a webworm infestation. Look for small silken webs and tiny caterpillars. The earlier you can catch an infestation, the easier it will be to manage.
Maintain Tree Health: Healthy trees are more capable of surviving a webworm infestation. Regular watering, proper fertilization, and timely pruning can help keep your trees healthy and resilient.
Biological Controls: Consider introducing or encouraging the presence of natural predators such as birds and beneficial insects (like parasitic wasps) that prey on webworms.
Tree Selection: If webworms are a consistent problem in your area, consider planting tree species that are less desirable to webworms when landscaping.
Manual Removal: If you see webworm webs, consider manually removing them by pruning the infested branches, if feasible. Dispose of the material in a sealed bag to prevent the caterpillars from returning to the trees.
Professional Pest Control: If you have a large or persistent infestation, you may want to consult with a professional pest control service or a local extension service. They can provide additional guidance and potentially apply appropriate insecticides.

Remember, although they can be a nuisance and may cause cosmetic damage, healthy trees can typically withstand webworm infestations and recover the following season.