What Type Of Conditions Cause Tent Caterpillars To Thrive

Forest tent caterpillars

Throughout Minnesota, forest tent caterpillars prey on a variety of broadleaf trees and plants, including quaking aspens, balsam poplars, basswoods, oaks, ashes, birches, alders, and fruit trees, among others.

  • The feeding damage caused by these caterpillars causes the development rate of deciduous trees to slow down. When forest tent caterpillars defoliate their target trees, they may cause damage to other adjacent plants as well. On vegetables, fruit trees and other tiny fruits, as well as nursery crops, there is evidence of damage
  • When they are discovered in close proximity to buildings or on roads, they become a nuisance.

The forest tent caterpillar (Malacosoma disstria) may be found throughout most of the United States and Canada, where hardwood trees can be found in dense stands of foliage. Red maple and conifers, such as pine and spruce, are among the plants on which this caterpillar is less likely to feed. Larvae of the forest tent caterpillar

How to identify forest tent caterpillars

  • Two inches long, primarily blue and black in color, with a row of white, footprint-shaped marks on the back and a dense covering of hairs along the edges of their bodies.

Adult moths

  • Moths are nocturnal and drawn to lights at night
  • They emerge from their cocoons around two weeks later, in mid-July
  • And they have a short lifespan.

Caterpillar egg mass in a forest tent

Life cycle of forest tent caterpillars

Aspen leaves begin to open in early to mid-May, which coincides with the emergence of larvae (caterpillars) from egg masses on the aspen tree.

  • Over a period of five to six weeks, aggressively feed on aspen and other broadleaf trees a silken mat that is hardly discernible where caterpillars congregate on the tree’s trunk and branches

As the month of June approaches, older larvae begin to roam about trees and other vegetation in search of food, causing harm to adjacent plants.

  • By the end of June, fully grown caterpillars are searching for safe havens to spin silky cocoons
  • By the middle of July, adults have emerged from their cocoons
  • Adults live for about five days and lay 100 to 350 eggs in gray, cylindrical masses surrounding small twigs
  • By the end of August, the caterpillars have hatched.

The eggs survive the winter, and the larvae that emerge from the eggs the following spring. Every year, just one generation is produced. The forest tent caterpillar is responsible for some defoliation.

Damage caused by forest tent caterpillars

Generally, feeding by forest tent caterpillars does not cause deciduous trees to die since they may develop another set of leaves during the same season in which they were fed. Healthy trees may withstand two to three years of intensive defoliation in a row if they are in good condition. Trees may be felled for the following reasons:

  • If the same tree has been significantly defoliated for four or more years, it is considered to be diseased. When trees are under stress, such as during a drought, they might die.

The forest tent caterpillar has completely defoliated the woodland.

Forest tent caterpillars as a nuisance

Maturity larvae can be seen on buildings and in yards when they are searching for a safe haven to lay their eggs.

  • They do not bite or hurt people, animals, or property
  • Instead, they are peaceful. There are several difficulties in removing their cocoons from the exterior of buildings, and they are a nuisance. If forest tent caterpillars on city roadways are mistakenly squashed, the resulting oily and slippery surface can be dangerous.

Scophaga aldrichi is a huge gray fly that preys mostly on forest tent caterpillars. When enormous numbers of forest tent caterpillars are discovered, the fly’s population grows exponentially. This fly does not bite and is completely harmless; yet, it is a nuisance since it will settle on any item, including people, and may cause irritation. This bug is critical in putting a stop to a forest tent caterpillar infestation on a natural basis.

How to protect your trees from forest tent caterpillars

  • The population of forest tent caterpillars is reduced by a cold or damp spring, hunger, and viral illness. In order to destroy caterpillar eggs, larvae, and pupae in a forest tent, wasps and flies must be allowed to flourish within the tent. A good example is the giant gray fly, Sarcophaga aldrichi, which is endemic to Minnesota and is considered a pest.

Remove eggs and caterpillars as you see them

  • Remove and destroy egg masses that have accumulated on the limbs of tiny trees before the eggs hatch the following spring. With a stiff brush, remove caterpillars and cocoons from the outside of houses, picnic tables, and decks. Using a water spray, knock caterpillars from their perches. Care should be taken not to crush too many caterpillars as this might cause smearing and marking on some paints.

Using pesticides

Pesticides, in addition to physical measures, may be effective in the control of larvae. Pesticides should be used while larvae are little (1 inch or less in length), which is often in early to mid-May. Larger larvae are more difficult to destroy, and they can continue to defoliate trees even after insecticides have taken their toll. Some of the choices that are accessible are as follows:

  • Bacillus thuringiensis (commonly known as BT), a microbial pesticide derived from a bacterium, is both efficient and friendly to the environment. Additionally, insecticidal soap, spinosad (a microbiological pesticide), and azadirachtin (a botanical pesticide) are among the pesticides that help to conserve beneficial insects. A number of chemical insecticides, including acephate, bifenthrin, carbaryl, cyfluthrin, esfenvalerate, fluvalinate, lambda-cyhalothrin, malathion, permethrin, and phosmet, have been developed to combat these pests.

When selecting a pesticide, take sure to read the label carefully because the active components are written in small type.

Forest tent caterpillars in wood lots

Birds, rodents, and even bears consume the caterpillar larvae of the forest tent caterpillar in wooded areas. Control actions should only be performed in the event of severe defoliation over a period of several years. In wooded regions, resort areas, and campsites where huge areas may require treatment, the following procedures should be followed:

  • Aerial pesticide spraying by aircraft is the most efficient, effective, and cost-effective approach available
  • Nevertheless, spraying should be avoided where gusts threaten to carry the pesticide over open water or other sensitive locations. Treatment of an extra strip about 400 feet wide next to the region should be performed when spraying in residential or recreational areas. The presence of this barrier strip prevents caterpillars from migrating.

The pesticide BT is recommended because it is non-toxic to humans, birds, or beneficial insects, and it is typically used first in aerial spray programs because of this property. Diflubenzuron should not be used near wetlands or bodies of water since the pesticide has the potential to harm aquatic insects and other arthropods. DISCLAIMER: The mention of a pesticide or the application of a pesticide label is solely for educational reasons.

Always read and follow the pesticide label recommendations that are connected to the pesticide container that you are currently working with. Keep in mind that the label is the law. In 2018, a review was conducted.

Tent Caterpillars: Insect & Disease Fact Sheets: Forest Health & Monitoring: Maine Forest Service: Maine DACF

The Eastern Tent Caterpillar in PDF format Photo courtesy of the Maine Forest Service’s Forest Health Monitoring Photographic Archive.

Eastern Tent Caterpillar,Malacosoma americanum(F.)

During the month of May, the eastern tent caterpillar may be found in the crotches of wild cherry and apple trees along roadsides, hedgerows, and the borders of fields, where it will spin webbings or tents. In early May, when the baby caterpillars hatch and the buds begin to open, these tents become visible for the first time. As the larvae develop, these tents become larger, and the backs of the caterpillars are coated with light brown hairs, with a row of oval, pale blue dots on either side of the caterpillar’s body.

The eggs will stay in this stage until the next spring.

Larger webbing on the extremities of hardwood tree branches in July and August is created by distinct caterpillars known as the autumn webworm, which feeds inside a tent on the ends of the branches of the trees.

Forest Tent Caterpillar, Malacosoma disstria(Hubner)

Caterpillars of the Forest Tent Photo courtesy of the Maine Forest Service’s Forest Health Monitoring Photographic Archive. The forest tent caterpillar has a life cycle that is similar to that of the eastern variety, but it does not build a tent. It is often found in wooded areas on oak, poplar, maple, or birch trees, where it may be a significant problem. Mature larvae are distinguished by a row of white keyhole marks on their backs, but otherwise resemble the eastern tent caterpillar in appearance and behavior.

Control *

The tents of the eastern tent caterpillars can be removed and destroyed by hand in small trees where they are found. Forked sticks or sticks with nails in them can be used to enter into bigger webs and twist them off of the branch by twisting the stick in two directions. It is better to complete this task early in the season before the tents become very enormous. Controlling eastern tent caterpillars on apple trees can be accomplished with the use of a fruit tree spray. The application of Bacillus thuringiensis (Bt), a microbial product, or carbaryl at the appropriate period can effectively control both the eastern and forest tent caterpillars.

  • Sevin should not be used in places where honey bees are kept as a pest control measure.
  • If you want the greatest results in central Maine, you should apply controls about May 20.
  • Before using any pesticide, make sure you read the label.
  • Use extreme caution while applying pesticides, both for your personal safety and the preservation of the environment.

Maine’s Department of Agriculture, Conservation, and Forestry (MAINE DEPARTMENT OF AGRICULTURE, CONSERVATION, AND FORESTRY) april 2000 – Maine Forest Service – Forest Health and Monitoring Division More information may be found at: PestAlertBugWood: Eastern Tent Caterpillar (USFS PestAlertBugWood) BugWood: Caterpillar of the Forest Tent

Forest tent caterpillars can cause significant defoliation on landscape trees

Despite the fact that forest tent caterpillars may cause defoliation of a wide variety of landscaping trees, homeowners are rarely required to take preventative steps. Infrequent but major defoliator of many hardwood tree species, the forest tent caterpillar (Malacosoma disstria) is a caterpillar that lives in the forest canopy. Natural reasons like as famine, sickness, and natural enemies usually cause population breakouts to linger for two to three years until they are brought to a conclusion.

Photo 1. Forest tent caterpillar.Photo credit: Gerald J. Lenhard, Louiana State University, Bugwood.org

Healthy trees are able to endure defoliation and put forth a second flush of leaves after the caterpillars’ feeding season finishes in June during outbreak years, but unhealthy trees are unable to do so. They may not look their best for the remainder of the year, and their development may be slowed, but they are resilient and can overcome their difficulties. In fact, any old tree has most certainly done it on more than one occasion in the past. Defoliation by forest tent caterpillars, which may be a role in hastening the eventual demise of weak trees that are already suffering from old age, illness, or damage sustained during construction or road work, is a natural risk for more severe consequences.

It is not necessary to control the forest tent caterpillar in order to sustain the long-term health of forested ecosystems.

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Many individuals who live in the outbreak regions complain about the annoyance caused by the roaming caterpillars, as well as the silk and droppings they leave behind.

The effectiveness of the treatment will be determined by the size of the treated area; wandering caterpillars from outside the treated area may still be a significant annoyance later in the season.

Management options for particular situations

Agricultural lands; forested lands Aerial pesticide treatments are the only realistic method of controlling pests in wooded regions if such control is needed. Typical pesticides for such purposes include Dipel and Thuricide, which are based on a strain of a naturally occurring bacterial pathogen (Bacillus thuringiensis, or B.t.) that only affects caterpillars of moths and butterflies, as well as other related products. B.t. insecticides are stomach poisons that must be swallowed by the caterpillars in order for them to be effective against them.

  1. Few other moth and butterfly species are destroyed on a rare occasion when insecticides are sprayed to tree canopies via airborne spray.
  2. sprays is often sufficient to alleviate excessive defoliation and the annoyance of caterpillars in the field environment.
  3. Sprays should be administered after all of the eggs have hatched, but before the caterpillars reach an inch in length, because older, bigger caterpillars are more difficult to kill than younger, smaller caterpillars.
  4. Caterpillars on individual landscaping trees can be treated with high pressure fluid sprays from ground equipment that uses B.t products or other chemicals to kill forest tent caterpillars on individual trees.
  5. This procedure is both time-consuming and expensive, and it also has the potential to do major damage to the tree if it is not carried out using precise equipment.
  6. Caterpillars that are older will congregate on the trunks of trees to rest for a while.
  7. To a certain extent, banding tree trunks with a substance that will prevent the passage of caterpillars can be beneficial.

Never apply a sticky substance directly to the trunk of a tree, since some products can cause damage to the bark, causing the tree to suffer more harm than the caterpillars would have done otherwise.

Caterpillars that are on the go.

For a variety of reasons, they frequently scale the walls of buildings and then rest there for extended periods of time.

sprays is ineffective in these cases since the insects are not eating while resting on the structures.

Pesticide soaps are a safer alternative, but they must be administered directly to the caterpillars’ bodies in order to be effective.

Sweeping newly deceased or alive caterpillars will result in streaks of a stain that is extremely difficult to remove.

When forest tent caterpillar numbers are large, the sheer amount of caterpillars can be so overwhelming that they become a shambles, whether they are dead or still living.

Their corpses will ultimately decay and return to the environment.


During the cocoon stage, there are no effective control strategies that may be used.

In order to destroy the adult moths that are produced by the forest tent caterpillar, there are no spray options available.

In order to prevent drawing large numbers of the moths to an area during their flying season, it is recommended that bright yard lights be turned off at this time. For a couple of weeks in June or July, the adults are generally out on the wing.

Photo 2. Forest tent caterpillar adult moth

Forest tent caterpillar adults are caught in traps, which are occasionally cited as a feasible management strategy for the forest tent caterpillar. Regardless of any marketing promises that may be made, the adult forest tent caterpillar traps will have no substantial influence on the population levels of the insect in question. It is only males of the species that are attracted to the traps, and they do not remove enough males from the ecosystem to have a significant impact on the overall rate of mating and reproduction.

The eggs of forest tent caterpillars are placed in clusters around the short stems of host trees, forming a ring around the stems.

Photo 3. Forest tent caterpillar egg mass.Photo credit: Steven Katovich,USDAForest Service, Bugwood.org

Wizzie Brown contributed to this article. Tent caterpillars attack a variety of broadleaf trees and shrubs, causing unattractive webs, or tents, to appear on the leaves. When their populations reach a critical mass, the caterpillars can defoliate trees, causing them to develop more slowly. They prey on ornamental and fruit trees, among other things. Early and correct identification of tent caterpillars, knowing their life cycle, and the use of suitable cultural or chemical management strategies are all essential for their eradication from the environment.

The eastern tent caterpillar, Malacosoma americanum, is the most troublesome of the four.

Life Cycle

Female moths lay their egg masses on tree trunks or tiny twigs throughout the late spring to early summer period (Fig. 1). The females of all Texas species, with the exception of the Sonoran tent caterpillar, utilize spumaline, a sticky, foamy substance, to “glue” the eggs to the bark or twigs of trees and shrubs. The spumaline also functions as a protective shell surrounding the egg mass, providing a firm, durable surface. During the majority of the summer, fall, and winter, egg masses linger on the branches of the trees.

  • Eastern and western tent caterpillars begin feeding on these fresh leaves within a few days of their appearance.
  • In most cases, the web is situated in the crotch of tiny limbs (Fig.
  • Because the larvae wander away from their tents to feed on leaves, harm can occur even if the web is located a long distance away from the tents.
  • These enormous, noticeable webs are created by the eastern and western tent caterpillars.
  • The larvae molt, or lose their skin, multiple times throughout their development.
  • The color pattern can also alter from instar to instar depending on the species.
  • 3).
  • Between feedings, dozens of caterpillars may assemble on these mats to wait for their next meal.
  • Protected areas like as the web, under the bark, among dead plant material on the ground, within a curled leaf, or under the eaves of homes are all common locations for spiders to hide.
  • Generally speaking, cocoons are loosely made of silk with a white or yellowish crystalline component dispersed throughout the whole thing.
  • Tent caterpillars in their adult form are brown and yellowish moths with two diagonal patterns on the front wings of their bodies (Fig.

4). Their wingspans are around 1 inch in length. They are drawn to lights, like do other moths. A single generation of tent caterpillars occurs once a year in all species. Adults only survive for a few days, during which time they mate, lay eggs, and do not consume any food.


Tent caterpillars in its infancy are brightly colored and grow to be approximately 134 inches long when fully grown. The only lengthy hairs on their body are found around the sides and on the back. Individual species may be distinguished by the colors and patterns on their larvae. If you come across tents with larvae that do not fit the descriptions in Table 1, it is most likely that they are autumn webworm tents. Fall webworms may construct tents throughout the late summer and fall and can have numerous generations per year, depending on the species.


The degree of defoliation, unattractive webs, and nuisance caused by the caterpillars should be taken into consideration when developing a management strategy. It is possible that you may need to utilize a combination of cultural and chemical procedures to achieve the optimum results. Control over one’s culture. During winter pruning, look for egg masses, which show as swellings on tiny, naked branches and are a sign of infestation. When trees are pruned, the tent caterpillar eggs are frequently removed before they develop.

  • When you discover spider webs on twigs in the spring, prune them as soon as you notice them.
  • It is not suggested to burn the web or caterpillars since it is quite dangerous.
  • Remove the dead caterpillars from the ground and dispose of them.
  • Beneficial insects can help to lower the number of tent caterpillars.
  • Trichogramma species prey on the eggs of tent caterpillars.
  • Control through chemical means.
  • The use of insecticide is pointless if the tent caterpillars have been allowed to feed and develop to completion.

Tents are weather-resistant and will remain in the tree for an extended period of time until they are removed.

Early morning or late evening applications are recommended in order to concentrate the spray on the tents when the caterpillars cluster.

The species that may be sprayed with these oils will be listed on the label of the product.

Some organically generated goods contain active substances such as Bacillus thuringiensis (Bt)varietykurstaki, spinosad, or insecticidal soap, which are all derived from bacteria.

In order for the Bt kurstaki and spinosad to be taken up and consumed by the caterpillars, spray the plant well before applying the substance to the leaves.

Contact-kill insecticides such as insecticidal soap must be applied directly to the caterpillars in order for them to be killed.

Some of these formulations operate when they come into direct contact with the pest, while others may have an oil-based component that is comparable to horticultural (petroleum-based) oils in their composition.

There are several long-lasting, synthetic pesticide solutions available that give quicker and longer-lasting control than most plant-derived insecticides while also working on all phases of the caterpillar’s life cycle.

Bifenthrin, cyfluthrin, esfenvalerate, fluvalinate, permethrin, lambda-cyhalothrin, indoxacarb, acephate, and carbaryl are all active chemicals to search for in a pesticide formulation.

Pesticide users are accountable for the impact pesticides have on their own plants or home goods, as well as any difficulties that may arise as a result of pesticide drift from their own properties to the properties or plants of their neighbors.

Also prone to change are the regulations governing the use of insecticides and pesticides. Always read and carefully follow the instructions on the product label for the most dependable instructions.


The author would like to express his gratitude to Bart Drees, Glen Moore, and Kim Schofield for their contributions to the review of this article. Bart Drees provided all of the photographs. Download a printer-friendly version of this publication by clicking on the following link: Caterpillars of the Tent »See more details about Gardening and Landscaping» Do you have a question – or do you require the assistance of an expert? Make contact with the appropriate county office.

Eastern Tent Caterpillar

Unlike other tent caterpillars, eastern tent caterpillars are black in color, slightly fuzzy, and have lighter stripes along their sides. They congregate in silvery-gray webs, which are commonly seen near the fork of a big branch on a tree or shrub’s main trunk. To see photographs and videos of caterpillars and their tents, please visit this page. The larvae and tent of the eastern tent caterpillar. Tammy Curley captured this image.

Life cycle of eastern tent caterpillars

Eastern tent caterpillars reproduce just once a year, resulting in only one generation. During the summer, the female moth deposits egg masses on the branches of host plants, and the eggs hatch. Eggs do not hatch until the next spring, generally in April, depending on the temperature of the surrounding environment. For 4 to 6 weeks, the caterpillars will feed on the leaf of the host plant. During the day, the caterpillars eat on buds and other plant materials. On gloomy or rainy days, as well as at night, the caterpillars remain within the limits of the tent, where they are safe.

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As a result, the tents become increasingly visible in the landscape, orchard, and along roadsides.

Large numbers of roaming caterpillars in close proximity to residences can be a source of anxiety, but they have finished eating and no further control is required at this time.

Damage caused by eastern tent caterpillars

Carrion caterpillars eat on the buds and leaves of a wide variety of trees and shrubs, but their favorite foods are the fruits of apple, crabapple, wild plum, cherry, and other closely related plants.

Management of eastern tent caterpillars

Tents and caterpillars may be removed and destroyed as soon as they are discovered, hence reducing the amount of damage. It is best to remove the tents in the early morning or late evening, or on chilly, wet days, when the caterpillars are not present in the tents. The caterpillars and silk webbing are completely harmless to humans; there is no danger in pulling down the tent with your bare hands, however many people like to use a paper towel or gloved hands to remove the tent and caterpillars off the ground.

In most cases, insecticides are useless against fully developed caterpillars.

If there are no caterpillars present, the tent is likely to be old and hence does not require treatment. You may see a video from the Dubuque County Extension Office about how to remove eastern tent caterpillars from your home orchard by clicking on the link below.

Caterpillars often confused with the eastern tent caterpillar

In addition to the eastern tent caterpillar, there are many other caterpillar species that are sometimes mistaken with it, including the forest tent caterpillar, the fall webworm, and the bagworm. It is a closely similar but distinct species, theforest tent caterpillar (Malacosoma disstria), that has been known to cause widespread outbreaks, with vast populations significantly defoliating wooded regions, every few years. These outbreaks are more prevalent in northeastern Iowa than anywhere else in the state.

Even though fall webworms (Hyphantria cunea) and other caterpillars are not closely related, the caterpillars eat as a group and weave a silken ‘tent’ or web in the branches of trees.

In addition, fall webworms are active considerably later in the year, and are first observed in August and September.

With the head and legs protruding out of the open top end of the bag, each caterpillar creates a bag that it totes around with it while it feeds.

Do you live in Iowa and have an insect you would like identified?

A visit to the Iowa State University PlantInsect Diagnostic Clinic can identify your bug and offer information on what it eats, its life cycle, and, if it is a pest, the most effective methods of controlling it. You may find updated forms, costs, and directions for preserving and sending insects on our website. Please check our website for more information. Residents of the United States can get in touch with the diagnostic laboratories in their respective states. It is important to note that if you live outside of Iowa, you should not submit a sample without first contacting the PlantInsect Diagnostic Clinic.

Tent Caterpillars

ENTFACT-424: Tent Caterpillars|Download the PDF version of this fact sheet

by Joe Collins, Nursery Inspector University of Kentucky College of Agriculture

Tent caterpillars are nocturnal creatures that dwell in groups under a silken tent. The silk is generated by glands in the head, and the tent protects the creature from a variety of natural predators and predatory insects. Tent caterpillars are found in three different species in Kentucky, the United States: the eastern tent caterpillar, the forest tent caterpillar, and the autumn webworm. Each of these pests has a diverse range of natural enemies that, in most cases, prevent caterpillar populations from getting excessively numerous.

During certain years, one or more of the species may, on the other hand, become quite prevalent.

Despite the fact that the defoliation and webbing are ugly, these insects seldom cause a tree to die. However, excessive feeding within a single year may cause tree development to be stunted, particularly if the tree is subjected to additional pressures such as drought.

Eastern Tent Caterpillar

Larvae of the ETC A native bug, the eastern tent caterpillar was originally described in 1646 and has been around ever since. The appearance of large numbers of this caterpillar is frequently associated with intervals of around 10 years. For a long time before the gypsy moth was unintentionally imported into the United States, the eastern tent caterpillar was thought to be one of the most serious pests of shade trees in our country. Among the fruits that eastern tent caterpillars like are wild cherry, apple, and crabapple.

  1. They will also eat The bug hibernates as an egg during the winter.
  2. The egg masses are approximately 3/4″ in length and have a varnished appearance.
  3. Following the hatching of their eggs, the little caterpillars proceed to create a tent in a nearby branch fork.
  4. The larvae crawl out of this tent and into the surrounding vegetation to feed.
  5. The larvae are usually black with a white stripe running down the back of their bodies.
  6. This insect pupates inside of whitish-colored cocoons that may be seen on tree trunks, fences, and buildings, amongst other places.
  7. The moths are reddish-brown in color with two white lines running across each wing on each of their wings.
  8. Tent (on the left) and ETC Egg Mass (on the right) (right)

Forest Tent Caterpillar

Larvae of the Federal Trade Commission The woodland tent caterpillar resembles the eastern tent caterpillar in appearance and behavior. The egg masses are laid in a manner identical to that of the eastern tent caterpillar, with the exception that they are square at the ends. When the eggs hatch, the larvae attach themselves to the trunk or limb of a tree and form a loose tent or mat. As a result, they will normally travel to the top of the tree where they will begin feeding on the developing leaves buds.

  1. A typical eating pattern for the larvae is to focus their feeding on a single branch at a time.
  2. In comparison to the eastern tent caterpillar, this caterpillar is differentiated by the keyhole-shaped markings that run along its back.
  3. Larvae are about the size of a pea.
  4. Each of the front wings has two dark brown stripes on each side, and the adult is a tan moth approximately 1-1/2 inches long with two dark brown stripes on each side.

Every year, there is a new generation. Sweetgum, oak, birch, ash, maple, elm, and basswood are among the trees that have been damaged by this insect.

Fall Webworm

In the United States and Canada, the autumn webworm is a pest that may be found throughout the majority of the country. With the exception of evergreens, it will feed on practically all shade, fruit, and decorative trees. The American elm, maples, hickory, and sweetgum are among the trees that are particularly popular in Kentucky. Larvae of the Fall Webworm When compared to the eastern tent caterpillar and the forest tent caterpillar, the autumn webworm is distinguished by the fact that it always places its tent at the ends of branches and that there is generally more than one generation every year of development.

  • They can have either a red or a black head on their bodies.
  • A frail web will be formed by the blackheaded larvae, but a huge and thick web will be formed by the redheaded larvae.
  • The moths begin to emerge between the middle of March and the middle of late April.
  • Female moths lay their eggs on the underside of leaves in masses ranging from 200 to 500 eggs in size after mating.
  • The first generation of caterpillars begins to feed from the middle of spring through the beginning of summer.
  • Defoliation caused by webworms is often greater in the second generation than in the first generation.


Essentially the same methods are used to control all three of these pests. It is quite effective to destroy the tents, especially if the tents are tiny, in order to get rid of the caterpillars. If possible, wait until dusk or early morning when the larvae are most active in the tent before doing this. It is best not to burn the tents since the tremendous heat and flames may cause harm to the tree’s roots. It may be necessary to prune egg masses off smaller trees in order to prevent their reproduction.

  • These caterpillars are resistant to the bacteria Bacillus thuringiensis (Bt) as well as a variety of chemical pesticides.
  • When the insects are in the nest, it is best to apply the pesticide in the evening or early morning when they are most active.
  • 1/04 – Date of last revision: CAUTION!
  • Some goods may not be legal to use in your state or nation, depending on where you live.
  • The photographs of the Eastern tent caterpillar tent and egg mass, the forest tent caterpillar larva, and the fall webworm tent were taken from the CD: G.K.
  • I and II, Southern Cooperative Series Bulletin No.
  • Douce, et al., 1995, Forest Insects and Their Damage Vol These are photos that have been copyrighted.

A signed license from the SFIWC and each individual photographer or organization is required before any commercial or other usage of the photos can be made.

Eastern Tent Caterpillar

Bugwood.org is run by Tim Tigner of the Virginia Department of Forestry. Malacosoma americanum is a kind of fungus found in the United States (Fabricius) Since 1646, people have been observing the eastern tent caterpillar in the United States of America. Outbreaks are common at eight- to ten-year intervals, and they can be deadly. Nests or tents formed in the forks and crotches of a tree, which are normally visible in the spring, are usually indicative of the existence of this insect in the area.

However, this was not the case.


Image 1: The Eastern Tent Caterpillar (Malacosoma americanum) in its natural habitat (Fabricius). Egg mass of the eastern tent caterpillar. R.L. Anderson of the USDA Forest Service (UGA0590063b) is credited. Fig. 2: Eastern Tent Caterpillar (Malacosoma americanum), in its natural habitat (Fabricius). The larvae of the eastern tent caterpillar. University of Georgia (UGA0795040b); G.J. Lenhard – Louisiana State University * The University of Georgia, as well as the individual photographers and organizations who created these photographs, have copyright protection for them.

  1. The egg mass may measure nineteen millimeters in diameter.
  2. The size of the tent increases in proportion to the number of larvae.
  3. After reaching maturity (Image 2), the caterpillars will depart the host tree in search of a suitable location to spin their pale yellowish cocoons.
  4. Following mating, the female lays eggs in a mass around little twigs on a host plant, which she later consumes.

Life History

This important pest overwinters as a black, shimmering egg mass on twigs that resembles a collar. Every egg mass contains between 150 and 350 eggs. The gregarious larvae begin to build their tents on surrounding branch crotches shortly after hatching from their eggs in the spring, about the time cherry leaves begin to emerge from their buds. These tents, which are constructed of silken layers, serve as safe havens for larvae during their development. A period of six to eight weeks is required for the caterpillars to complete their feeding cycle.

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The larva undergoes a transformation into a resting stage known as the pupa while enclosed in the cocoon.

Approximately three weeks pass during the pupal stage. A female lays eggs in a swarm around little twigs throughout the months of June and July, when the adults first emerge. In Pennsylvania, there is just one generation of children every year.


Overwintering as a black, shiny, collar-like egg mass on twigs is how this important pest is recognized. There are 150 to 350 eggs in each egg mass. The gregarious larvae begin to build their tents on surrounding branch crotches shortly after emerging from eggs in the spring, about the time cherry leaves begin to emerge from buds. Designed to shelter larvae from predators, these tents are constructed of silken layers. Six to eight weeks pass between the time the caterpillars feed and when they stop.

The larva undergoes a transformation into a dormant stage known as the pupa while enclosed in the cocoon of protection.

A female lays eggs in a mass around small twigs during the months of June and July, when adults emerge.


The larvae of the eastern tent caterpillar are prey for a variety of different insects, toads, and birds. Several species of tiny, helpful wasps prey on the eggs, larvae, and pupae of this pest, causing them to die. During bad weather conditions, a large number of caterpillars succumb to illness. From December through March, prune short twigs that contain viable egg masses on them to ensure that the eggs hatch successfully.


Registered pesticides should be used in April, when the caterpillars are at their earliest stage of development. To manage the eastern tent caterpillars, apply registered formulations to the nests as well as around one foot of the surrounding branches or trunk to achieve effective control. Apply the spray before the nests have grown to a diameter of three inches. If at all feasible, apply pesticides first thing in the morning, when the caterpillars are most likely to be within their nests. To get precise information on host plant label clearance, phytotoxicity information, safety precautions, and dose information, read and follow all label requirements carefully.


Pesticides are extremely toxic. Read and adhere to the instructions and safety precautions provided on labels. Precautions should be taken when handling and storing the product in original labeled containers out of the reach of children, pets, and animals Empty containers should be disposed of as soon as possible in a safe manner and location. Don’t pollute forage, streams, or ponds with chemicals. The following article was written by: Gregory A. Hoover, Sr. Extension AssociateMarch 2002

Eastern Tent Caterpillar, Malacosoma americanum

In the early spring, the tents of the eastern tent caterpillar are a striking sight to see. A common sight in early April in Wisconsin is the eastern tent caterpillar (Malacosoma americanum), sometimes known as the tent caterpillar. A colony of caterpillars builds the white mounds in the forks of tree branches that you see in the photo. They are protected by the tent from predators such as birds as well as from excessive temperatures. They emerge out of their silken webs to eat in the early morning, late afternoon, or early evening when the temperature is not too low.

As the caterpillars increase in size, the nest grows in size as well.

This species is more common later in the season; it feeds on almost all shade and fruit trees with the exception of conifers; its nests are located at the ends of branches rather than in branch crotches; and its loosely woven webs enclose foliage in contrast to the eastern tent caterpillar’s tight-woven tents.

  1. Shiny egg masses are wrapped around twigs to create a beautiful display (top).
  2. The egg stage of the eastern tent caterpillar allows it to survive the winter.
  3. It is around the time of bud break that the larvae — caterpillars – hatch.
  4. In a colony, caterpillars from the same egg mass will stay together; in a big colony, caterpillars from two or more egg masses will join together to form a single enormous colony.
  5. As soon as they have finished eating, they leave the nest and weave a white or yellowish silk cocoon in a safe location like as tree trunks, fences, or buildings.
  6. When the ladies have finished mating, they lay their eggs on little branches that survive until the next spring.
  7. It is estimated that the population of this native North American pest fluctuates from year to year, with epidemics happening every few years.

Fruit trees, such as apple, cherry, blooming crabapple, plum, and chokecherry, are the most typically afflicted, with apple, cherry, and flowering crabapple being the most prevalent.

However, while severe infestations can result in significant defoliation, eastern tent caterpillars are seldom known to kill trees, with the exception of those that have already been compromised by disease, climate change, or other environmental pressures.

When it comes to tree health, the eastern tent caterpillar is more of an inconvenience than a danger.

Most trees will leaf out again within two or three weeks even if they have been entirely defoliated, because caterpillar feeding normally ceases during periods of high leafing activity.

It is also possible that the nests will become a nuisance in the landscape, particularly if they are exposed as a result of extensive defoliation.

When fully developed, the hairy caterpillars measure around 2 inches in length and have a prominent white line running down the back of their bodies.

When they are mistakenly squished on roads, driveways, sidewalks, and patios, they cause quite a commotion. It is easy to eliminate this insect issue when it is discovered early in the season.

  • During the winter, egg masses should be removed and destroyed. They may be removed from a branch by pruning or crushing it. Dormant oil sprays, when applied to huge trees with numerous egg masses, are extremely effective at suffocating the eggs and preventing them from hatching. Small tents should be removed by hand (while wearing gloves) in the early spring. Larger webs should be removed with a broom or a stick, and the webs should be disposed of with the caterpillars (crush, burn or bury them). To avoid re-establishing their colony, wait until the caterpillars have entered the nest before doing this. It is not recommended to attempt to burn tents on plants since this might cause more damage to the tree than the caterpillars themselves. Unless the caterpillars are more than one inch in length, you should only use a certified pesticide. Caterpillars beyond a certain size are less susceptible to insecticides since they have already completed the majority of their eating. Avoid using any treatments that might harm pollinating bees while the tree is in bloom – instead, use Bacillus thuringiensis (BT), which only affects caterpillars.

– Susan Mahr, University of Wisconsin – Madison– Phil Pellitteri, Department of Entomology, University of Wisconsin – Madison, took all of the photographs.

Fall webworm & Eastern Tent Caterpillar [fact sheet]

Obtaining a Downloadable Resource In addition to fruit, the autumn webworm (Hyphantriacunea) and the Eastern tent caterpillar (Malacosomaamericanum) eat on trees in woodlands and shadows. Orchards that are frequently treated with pesticide to combat codling moths and other pests have little need for them in terms of economic value. They can, however, be regarded a serious pest in nurseries and landscaping due to the unattractive webs they create. A common misconception is that the fall webworm is the same as the Eastern tent caterpillar.

For its part, the Eastern tent caterpillar’s web is densely packed into the forks and crotches of trees; the larvae do not feed within their webs, but instead cluster there at night and during wet weather.

Caterpillars of the eastern tent Image courtesy of Marie-Eve Jacques


Fall Webworm: When fully developed, the larvae measure around 1 1/2″ in length. Depending on the species, they may be yellow with dark stripes and dots or a drab blue black without any yellow. Their bodies are covered with hair, and their heads are dark in color. Adult moths have a wing span of around 1 1/2 inches. Their hue is almost completely white. The Eastern Tent Caterpillar has scant hairs and grows to be around 2 inches long when fully developed. A white stripe runs down the middle of the back of the animal, and it is painted black with white and blue patterns.

Life Cycle

Each year, a new generation of fall webworm is produced, but it is not particularly synchronized. The insects hibernate as pupae in the soil during the winter. The adult moths emerge from the earth throughout the months of June and July. In July, the females begin laying their massive clutches of eggs. The eggs begin to hatch towards the middle of July. The larvae eat within the web for a month or more before crawling down the tree and constructing a cocoon, where they will eventually pupate.

The insects overwinter as egg masses on twigs, and they hatch in April after spending the previous winter as egg masses.

As the larvae grow and mature, more layers of the tent are erected.

The females lay masses of eggs in bands around twigs, which are then eaten by the males.

The larvae of the fall webworm. Photograph courtesy of Ward Upham of Kansas State University. The larvae of the eastern tent caterpillar. Marie-Eve Jacques is credited with this photograph. The larvae of the eastern tent caterpillar. Photograph courtesy of Marie-Eve Jacques.


  • It is possible to limit the requirement for therapy by monitoring for and eliminating tent caterpillar egg masses. It is critical to discover webs of either insect as soon as possible in order to avoid significant defoliation. Destroy nests by trimming or removing them manually (a stick can be placed into huge webs and then twisted to remove the webs). Biological Control – A variety of natural enemies, including birds, small animals, insect predators, spiders, and parasitic wasps, keep the numbers of both the autumn webworm and the Eastern tent caterpillar under control. When the humidity and temperatures are just right, a naturally existing virus and a fungus can multiply to the point where they kill large numbers of caterpillars of both species. When dealing with either pest, biological pesticides based on the Bacillus thuringiensis (Bt) bacteria should be employed, and they should be administered as soon as the tents are spotted while the larvae are still young. Chemical Control – Use pesticides to control infestations that are difficult to reach or when populations are large. In order to receive particular pesticide recommendations, contact your county’s Agricultural Field Specialist.

Egg mass of the eastern tent caterpillar. Photograph courtesy of Alan T. Eaton. The Eastern tent caterpillar is responsible for the defoliation. Photograph courtesy of Marie-Eve Jacques. Stop! Ensure that you thoroughly read the label on every pesticide bottle before to utilizing the item. Pesticides must only be used in the manner specified on the label in order to be in conformity with the law. The continuous registration of all pesticides described in this book is conditional on their ongoing use.

New Hampshire rules require that empty containers be disposed of in an appropriate manner.

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