What are Fall Webworms?

Fall webworms are caterpillars that spin large webs over the foliage of trees and shrubs in the late summer and fall. They can be found on a variety of deciduous trees and can cause defoliation if left untreated.

There are two species of fall webworms:

1. Hyphantria cunea - The Eastern Fall Webworm, found throughout the eastern United States and parts of Canada.

2. Hyphantria textor - The Western Fall Webworm, found in the western United States and parts of Canada.

Both species of fall webworms are members of the Erebidae family and the Lepidoptera order, which includes moths and butterflies.

Host Plants

Fall webworms can infest a variety of deciduous trees and shrubs, including:

1. Fruit trees: Apple, Cherry, Pear

2. Shrubs and Trees: Ash, Birch, Dogwood, Hickory, Elm, Maple, Oak, Poplar, Rose, Sweetgum, Willow

Regions impacted

Fall webworms are found throughout North America, from Canada to Mexico, and can be a common pest in deciduous trees and shrubs in many regions. They are also found in parts of Europe, Asia, and Africa, where they may infest a variety of deciduous trees and shrubs. The specific species of fall webworms may vary depending on the geographic location, but they are generally found in areas with temperate or subtropical climates that support the growth of deciduous trees and shrubs.

Description

Fall webworms are caterpillars that spin large webs over the foliage of trees and shrubs in late summer and fall. The webs can be unsightly and cover large portions of the tree or shrub.

The caterpillars are hairy and can vary in color from yellow to brown or black. Despite their appearance, fall webworms are generally not harmful to the overall health of the tree or shrub.

Life Cycle

The life cycle of fall webworms begins in the spring when the adult moths emerge from overwintering pupae in the soil.

The moths mate and lay eggs on the undersides of leaves in late spring to early summer. The eggs hatch into small caterpillars that begin to spin webs over the foliage of the tree or shrub.

As the caterpillars feed on the leaves, they grow and expand their webs to accommodate their increasing size. The caterpillars molt several times as they develop and can go through multiple generations in a single season.

In the fall, the caterpillars spin cocoons within the webs and overwinter in the pupal stage in the soil.

The adult moths emerge the following spring to repeat the cycle.

Overall, the life cycle of fall webworms is completed in one year and can involve multiple generations depending on the geographic location and climate.

Damage and Detection

Damage: Fall webworms can cause damage to trees and shrubs by feeding on the leaves and defoliating the plant. The webs can also be unsightly and may cause concern for homeowners. However, fall webworms are generally not harmful to the overall health of the tree or shrub and do not usually require treatment unless the damage is severe.

Detection: Fall webworms can be detected by the large webs that they spin over the foliage of the tree or shrub. The webs can be up to two feet in diameter and may cover entire branches or sections of the tree. The caterpillars can also be seen within the webs, feeding on the leaves. If left untreated, the webs may become unsightly and may reduce the aesthetic value of the tree or shrub.

If you suspect that your tree or shrub has been infested with fall webworms, it is important to take action to control the population and prevent further damage. 

Prevention and Control

Here are some ways to prevent and control fall webworms:

1. Encourage natural predators: Many birds, such as blue jays and chickadees, feed on fall webworms and their caterpillars. You can attract these birds to your yard by providing birdhouses and birdfeeders.

2. Remove webs by hand: If you notice webs on your tree or shrub, you can remove them by hand using a stick or rake. Be sure to wear gloves and dispose of the webs and caterpillars in a sealed bag to prevent re-infestation.

3. Apply insecticides: If the infestation is severe, you can apply insecticides to control the population. Insecticides containing Bacillus thuringiensis (Bt) or spinosad are effective against fall webworms and are less harmful to beneficial insects and the environment.

4. Prune affected branches: If the infestation is limited to one or a few branches, you can prune them to prevent the further spread of the infestation.

5. Maintain tree health: Keeping your tree or shrub healthy and well-watered can help it resist infestation by fall webworms and other pests.