The Fall Webworm Moth, scientifically known as Hyphantria cunea, is a common pest found throughout the United States and southern Canada. These native North American insects are known for their feeding habits on a wide variety of shade, fruit, and deciduous ornamental trees, with some preferred hosts including American elm, birch, hickory, and some maples Wisconsin Horticulture.
In early spring, adult moths emerge, and females lay egg masses on the underside of leaves. As the caterpillars hatch and grow, they create conspicuous white webs around the leaves Clemson Home & Garden Information Center. These webs expand over tree branches throughout the summer and are an easily recognizable sign of their presence. The caterpillars are not only interesting to observe due to their defensive thrashing behavior when disturbed, but it is also essential to understand their impact on tree health and proper management techniques Purdue Extension Forestry.
Fall Webworm Moth Identification
Moth Characteristics
The Fall Webworm Moth, also known as the mulberry moth, belongs to the Erebidae family. This species is particularly active during the warmer months, typically between April and September. The moth exhibits some subtle variations in appearance depending on its location:
- Northern populations: Usually pure white, creating a bright appearance.
- Southern populations: White with dark wing spots.
The wingspan of these moths ranges from 25 to 40 millimeters, and they feature a hairy body.
Caterpillar Characteristics
Once the Fall Webworm Moth lays its eggs, caterpillars emerge and begin constructing their webbed nests. These caterpillars showcase distinct attributes:
- Color: Ranging from yellow to light green.
- Feeding habits: They feed on the surface of leaves during their early stages, progressing to devour entire leaves as they mature.
- Webbing: They create large tents around the leaves they consume.
Similar caterpillar species, like the Eastern Tent Caterpillar, also form tents around leaves, but the Fall Webworm is known to create significantly more extensive webbing. With their distinct characteristics, identifying Fall Webworm Moths and their caterpillars becomes simpler.
Life Cycle and Reproduction
Eggs
- Laid on the underside of leaves
- Moths lay up to 1,500 eggs
In spring, the adult Fall Webworm Moth lays eggs on the underside of leaves. A single female can lay nearly 1,500 eggs, which are covered with white hairs from her abdomen.
Larvae
- Caterpillars are pale green with long hairs
- Feeding on leaves
After hatching from the eggs, the larvae (caterpillars) start by feeding on the leaf’s surface. As they mature, the larvae, which are pale green with long hairs, devour entire leaves.
Pupa
- Overwinter in cocoons
- Found in mulch or soil
When fully grown, caterpillars transform into pupae within cocoons. The pupae overwinter in mulch or soil, remaining dormant until the following spring.
Adult Moths
- Appear in late June and July
- Multibrooded species; moths seen from early April to September
Adult Fall Webworm Moths, which are mostly white, emerge from their cocoons in late June or early July. The moths are active and reproduce throughout the season, making them a multibrooded species. The moths can be found from early April until September.
Comparison Table: Fall Webworm Moth Life Stages
| Life Stage | Characteristics | Time of Year |
|---|---|---|
| Eggs | Laid on underside of leaves, covered in white hairs | Spring |
| Larvae | Pale green, long hairs, feed on leaves | Spring to Summer |
| Pupa | Overwinter in cocoons, found in mulch or soil | Fall to Winter |
| Adult Moth | White, multibrooded, active from April to September | Summer to Fall |
Habitat and Distribution
North America
The Fall Webworm Moth, belonging to the family Erebidae, is native to North America, specifically the eastern regions. Its distribution extends from the US up to southern Canada, where it reaches its northern limit at latitudes between 50-55°1. In these areas, it is a common pest causing defoliation in deciduous trees and shrubs2.
- Native to Eastern North America
- Range extends to Southern Canada
Europe
The Fall Webworm Moth was introduced in Europe in the 1940s, first recorded in Yugoslavia3. Since then, it has spread across the continent, expanding its habitat and distribution in various European countries.
- Introduced in the 1940s
- Spread throughout Europe
Asia
In Asia, the Fall Webworm Moth has also established its presence. It has been reported in countries like China, North Korea, and Japan. The moth continues to be a concern for both forest health and agriculture in these regions.
- Present in China, North Korea, Japan
- Affects forestry and agriculture
Comparison Table: Fall Webworm Moth Distribution
| Region | Native/Introduced | Year of Introduction |
|---|---|---|
| North America | Native | – |
| Europe | Introduced | 1940s |
| Asia | Introduced | – |
Host Trees and Damage
Types of Trees
Fall Webworm Moths (Hyphantria cunea) are known to infest more than 100 species of deciduous forest and shade trees. Here’s a list of some common host trees:
- Hickory
- Willow
- Elm
- Walnut
- Birch
- Maple
- Ash
- Oak
- Persimmon
- Sweetgum
Their preference also includes fruit trees like cherry, apple, and pecan, as well as ornamental trees such as black cherry, American elm, and some shrubs.
Signs of Infestation
Fall webworms leave a few telltale signs on the trees they infest.
- Webs on branches: These small, pale-yellow caterpillars create large, conspicuous white webs on tree branches that grow over the course of the summer.
- Damaged foliage: As the caterpillars feed, they consume large amounts of foliage leaving behind skeletonized leaves.
Here’s a comparison table of different tree types concerning fall webworm susceptibility:
| Tree Type | Fall Webworm Susceptibility |
|---|---|
| Hickory | High |
| Willow | High |
| Elm | Moderate |
| Walnut | High |
| Birch | High |
| Maple | Moderate |
| Ash | Moderate |
| Oak | Moderate |
| Persimmon | Low |
| Sweetgum | High |
It is essential to observe trees for these signs to ensure timely management and control measures. Although the damage inflicted by fall webworms may not directly kill the tree, severe defoliation weakens the tree’s defense against other pests and diseases.
Control and Management
Natural Enemies
Many predators help keep fall webworm populations in check. Some examples include:
- Birds, which feed on the caterpillars
- Parasitic insects, such as wasps and flies
- Predatory insects, like ants and beetles
Cultural Control
Practicing good cultural control can reduce the impact of fall webworms on your plants. Key points for cultural control are:
- Promptly remove and destroy webbed branches
- Encourage natural predators by maintaining diverse plantings
In cases of light infestations, pruning infested branches or using a forked stick to remove webs can help.
Insecticides
Certain insecticides can be used to manage fall webworms, including:
- Permethrin
- Carbaryl
- Cyfluthrin
- Cyhalothrin
- Bacillus thuringiensis (Bt)
- Spinosad
It’s important to apply insecticides when caterpillars are young, and focus on the undersides of leaves where eggs are laid.
| Insecticide | Pros | Cons |
|---|---|---|
| Bacillus thuringiensis (Bt) | Safe for beneficial insects | Slow-acting |
| Permethrin | Fast-acting | Non-selective |
Keep in mind that using insecticides may harm beneficial insects, so it’s best to use them only when necessary.
Bug Control Recommendation Tool
Fall Webworm Moth vs Eastern Tent Caterpillar
Visual Differences
Fall webworm moth (Hyphantria cunea) and Eastern tent caterpillar (Malacosoma americanum) are two different species with distinct visual differences. Fall webworm caterpillars have:
- Light-colored bodies with black and yellow markings
- Long hairs, or tubercles, that protrude from their bodies
On the other hand, Eastern tent caterpillars have:
- Dark-colored bodies with a white stripe along their backs
- Shorter hairs and fewer tubercles
Behavioral Differences
These two species also exhibit different behaviors. Fall webworms:
- Create large silk tents at the ends of branches
- Are gregarious, feeding and living within their silk tents in large groups
- Feed on a wide variety of deciduous trees, including more than 120 different species
Comparatively, Eastern tent caterpillars:
- Build their silk tents in the crotches and forks of branches, rather than at the tips
- Also feed in groups, but are more conspicuous as they move across branches to find new feeding sites
- Preferentially feed on crabapple, hawthorn, and flowering cherry trees
| Feature | Fall Webworm Moth | Eastern Tent Caterpillar |
|---|---|---|
| Appearance | Light-colored with black and yellow markings, long hairs | Dark-colored with a white stripe, shorter hairs |
| Silk Tent Location | Ends of branches | Crotches and forks of branches |
| Feeding Preferences | Over 120 deciduous tree species | Crabapple, hawthorn, and flowering cherry trees |
In conclusion, understanding the visual and behavioral differences between fall webworm moths and Eastern tent caterpillars can help in identifying and managing these two species effectively.
Impact on Forestry and Ecosystem
The fall webworm moth is a known pest that has a significant impact on forestry and ecosystems. With their larvae feeding on more than 100 species of deciduous forest and shade trees, the infestation causes stress for tree species, including fruit trees such as apple.
To better understand the fall webworm moth, it is essential to look at the life stages. The larvae, or caterpillars, can have two appearances:
- Satin white with dark stripes and spots
- Dull bluish-black without yellow markings
Their main distinction is that both types have very hairy bodies. These larvae feed on tree leaves and build large, conspicuous web-like nests during late summer, which can be noticed in various tree species.
The fall webworm can have multiple generations, making infestations challenging to control. When allowed to thrive, it can cause significant damage to the trees, including complete defoliation. This increases the trees’ stress and negatively impacts the overall health of the forest ecosystem.
It is not just the local ecosystem that suffers due to fall webworm moths. The species is considered an invasive pest in Europe and Asia, affecting both ornamental trees and agriculture crops. This spread to other regions causes further strain on global ecosystems and forestry.
One way to manage fall webworm infestations is the introduction of parasitoids. These insects can help to control the pest population in a natural manner, without the need for chemical treatments.
In conclusion, the fall webworm moth’s impact on forestry and ecosystems cannot be underestimated. Damage caused by their larvae infestation can weaken individual trees, affect the health of forests, and even disrupt agricultural production. Implementing management strategies, such as parasitoid introduction, can help to mitigate these negative impacts and maintain a more balanced ecosystem.
Footnotes
