Identifying Hairy Caterpillars

PLEASE NOTE the hairs of some caterpillars can cause skin irritation so care should be taken to avoid direct skin contact.

As previously reported the hairs of Brown Tail caterpillars are particularly prone to causing quite a severe skin reaction.

Although most caterpillars have hairs, known as setae, they are often almost invisible to the naked eye, being pale and thinly spread.

Those with excessively hairy bodies make up only a small percentage of the different species of moth caterpillar found in the British Isles and North America

Below are some of the most commonly seen hairy caterpillars. Other less frequently seen hairy species and those with extraordinary tufts can be seen in the Moth Caterpillar Galleries.

There are no densely hairy butterfly caterpillars in the British Isles but several very ‘spiky’ species are shown in the Butterfly Caterpillar Galleries.

When using the caterpillar galleries it’s worth bearing in mind that some caterpillars dramatically change their appearance as they grow.

With each skin moult they can suddenly look very different.

Consequently young caterpillars may be take on a totally different appearance when fully grown.

As an example the image left is of an early instar (young) Oak Eggar moth caterpillar followed by two progressively later instars.

More help with identifying a caterpillar

As part of a caterpillar’s survival strategy the dense hairs offer some protection from predators enabling them to safely sit out in the open during the day.

Many species are most commonly seen when fully grown and walking across open ground looking for somewhere to pupate.

Below, starting with the fully grown Oak Eggar caterpillar, are some of the other densely hairy caterpillars often seen in the British Isles.

These photographs are all of fully grown caterpillars.

Introduction to rearing butterfly and moth caterpillars

How to rear caterpillars

Oak Eggar moth caterpillar

The Oak Eggar caterpillar grows to about 75mm and is commonly found in many parts of the British Isles.

It is commonest on open heath and moorland and not associated with oak trees as its name would suggest.

By late spring it is fully grown and can often be found lying on top of low vegetation.

In the colder north the caterpillar adopts a two year cycle.

Fox Moth caterpillar

The Fox moth caterpillar grows to about 65mm and is commonly found around the coast and in open country throughout much of the British Isles.

When fully grown it is often found in late spring basking on top of vegetation and on the bare soil of well worn paths.

This is another species where the early instar caterpillars look very different to the fully grown caterpillar.

The Lackey moth caterpillar

The Lackey caterpillar grows to 55 mm and is fairly common throughout most southern counties of the British Isles.

It is not the hairiest of caterpillars but has a band of thick ginger setae extending down its side.

When small it lives communally in a spun web that can be found in a variety of deciduous hedging and trees.

It is particularly frequent in coastal Blackthorn hedges.

The Drinker moth caterpillar

More information on The Drinker Moth caterpillar grows to about 65mm and may be found throughout most of the UK in open grassy habitat but is most common in the south.

It can often be found during the day amongst grasses and reed stems.

It is fully grown by May/June and may sometimes be found basking in the sun on stone walls and wooden posts.

Garden Tiger moth caterpillar

The Garden Tiger Moth caterpillar grows to about 55mm long and is often referred to as the ‘Woolly Bear’ caterpillar because of its long hairs.

It is common throughout most of the British Isles including urban gardens although its numbers seem to have declined sharply in recent years.

The Garden Tiger is also found in North America and in many states where it’s known as The Great Tiger Moth and one of several Arctiidae caterpillars called Woolly Bear caterpillars.

Cream-spot Tiger moth caterpillar

The Cream-spot Tiger moth caterpillar grows to about 65mm and is fairly common in open habitat in southern parts of the British Isles.

When fully grown in the early spring it may be found basking in the sun on grasses and herbaceous plants during the day.

The brown head helps identify it from other hairy caterpillars.

Ruby Tiger moth caterpillar

The Ruby Tiger moth caterpillar grows to about 35mm and has a fairly wide distribution throughout most of the British Isles but is more common in the south where there are two broods.

The Ruby Tiger is also found in parts of North America.

When looked at closely the hairs are light brown and sprout in tufts.

It can often be seen basking in the sun on low vegetation during the autumn and spring.

White Ermine moth caterpillar

The White Ermine moth caterpillar grows to about 45mm and is widely distributed throughout much of the British Isles.

It feeds on a variety of herbaceous plants and can sometimes be seen walking quickly across the ground looking for somewhere to pupate.

Looked at closely the hairs are not as dense as on some hairy caterpillars. An orangey thin line runs down its back but this is not always easy to make out amidst the hairs.

Buff Ermine moth caterpillar

The Buff Ermine moth caterpillar grows to about 45mm and is a common species found throughout most of the British Isles in a wide range of habitats.

The brown hairs can appear quite gingery in sunlight and the pale dorsal line extending down its back is not always clear to see through the setae.

A broader, pale band running down its side is more obvious, particularly if it rolls up on its side.

Pale Tussock moth caterpillar

The Pale Tussock moth caterpillar grows to about 45mm and is fairly common in the southern half of the British Isles.

The caterpillar feeds on a wide variety of deciduous trees.

The fully grown caterpillar can be various shades of green and yellow, with some caterpillars lacking the distinctive red hair tail spur. Is the tail spur dangerous?

Most often recorded in September and October when it may be found walking on the ground looking for somewhere to pupate.

The Sycamore moth caterpillar

Information on the Sycamore moth caterpillar.

The Muslin Moth caterpillar

Complete life cycle information illustrated with photographs of the Muslin Moth
More hairy caterpillars can be seen in the Moth Caterpillar Galleries, Butterfly Caterpillar Galleries and American Caterpillar Gallery.

Also included are the largest Hawk-moth caterpillars and many that are brightly coloured, cryptically camouflaged and extraordinarily shaped.

The Forestry Commission and animal welfare charities such as the Blue Cross, are urging visitors, residents and dog owners to stay away from processionary caterpillars which have been discovered nesting in Greater London and nearby areas in the UK.

The caterpillars are dangerous if touched and can be deadly to dogs and other pets due to their highly irritant hairs. The Forestry Commission is particularly concerned about the damage that the caterpillars cause to oak trees, as they’re infamous for stripping the trees bare of leaves, which leaves them vulnerable to attack from other pests or diseases. The organisation is also concerned about public health since the caterpillars present a threat to people, pets and livestock.

But what exactly is a processionary caterpillar? How can you spot them and what can you do if you stumble upon a nest? Read our guide to discover everything you need to know about the processionary Caterpillar.

What are processionary caterpillars and moths?

Recent news in the UK has focused on the oak processionary moth (sometimes called OPM for short), which are close relatives of the pine processionary moths. Scientifically speaking, they’re two different sub-species of the same family of insect (officially known as Thaumetopoeidae). Both types of moths originally come from warmer climates including Southern Europe and Northern Africa and it’s thought that they were accidentally introduced to the UK as eggs hidden in plants brought over from continental Europe.

These insects earn their name from their characteristic nose-to-tail “follow the leader” style of moving in large groups or processions. They’ll often move around like this to find a new location to nest or burrow, or in search of food.

The processionary moth lifecycle

Like many other insects, processionary moths go through several stages in their lifecycle before reaching adulthood.

  • Eggs: are usually laid in masses on oak trees during late summer and into September and hatch in early summer or spring.
  • Larvae: more commonly known as caterpillars, the larvae cause the most damage to trees and present a health risk to humans and animals. In this stage of the lifecycle, they build nests in trees and process in their characteristic nose-to-tail fashion.
  • Pupae: the last stage before emerging as a fully grown adult moth. The caterpillars (larvae) will usually process down the tree from their nest to pupate at ground level. Sometimes they’ll burrow slightly below the ground.
  • Adults: once they’ve emerged as adults from their pupate stage, they actually only live for up to two or three days. They’ll quickly mate and lay their eggs, restarting the lifecycle.

In the UK, it’s more likely to spot the larvae stage (caterpillar) processionary Moth during the months of May onwards and into the summer. By September, the pupation stage is usually complete and adult processionary Moths will emerge from their nests.

Why are they dangerous for dogs to go near them?

Processionary Caterpillars present dangers for curious pets, especially dogs who may go sniffing around underneath trees and may be fascinated if they spot a hairy creepy-crawly.

Processionary Caterpillars are covered in thousands of hairs, known as Urticating hairs or bristles (around 62,000 of them!). These contain a highly irritating protein that can cause severe allergic reactions. In the latter larvae stage of development (the caterpillars themselves go through six stages of moulting before entering the pupate phase) these hairs can be ejected or shed. Even when not attached to a caterpillar, these hairs can still cause incredibly nasty stings.

Where have processionary caterpillars been found?

The above map shows areas of London and the South East of England where processionary caterpillars have been discovered – the confirmed nests are red dots. The green line is the outer boundary of the affected area in 2016 and 2017.

The original outbreak of the caterpillars was discovered in West London and since then processionary caterpillars have been discovered or spread in other locations around London, including in parts of Surrey. The following areas are included in what the Forestry Commission is calling the ‘Core Zone’ where control action on oak trees is highly recommended and dog owners should be extra vigilant.

  • Ealing
  • Hammersmith & Fulham
  • Hounslow
  • Kensington & Chelsea
  • Kingston Upon Thames
  • Richmond Upon Thames
  • City of Westminster

For more information on infested areas and the treatment that the Forestry Commission is working on to stop the spread of these caterpillars, see the report on their website.

How to spot oak or pine processionary caterpillars and moths

The caterpillars are usually the easiest stage to spot. Not only do they move around in their famous processions, but they also leave tell-tale signs behind them such as build nests in the branches of pine or oak trees. In contrast, the processionary moth eggs are small (in clusters, known as plaques, around 3 cm long) often hard to spot as they’re a similar colour to tree bark. What’s more, the moths are brown, grey and white in colour, closely resembling the colour of oak tree bark, are difficult to distinguish from other moths and they only live for two to three days at most.

Tell-tale signs of a nearby processionary caterpillar population include:

    • Nests:

these are usually found in the branches of oak or pine trees. The nests are built from white, silky webbing and are half-sphere, ball or tear-drop shaped. They can be as small as a 50p coin (which would be very hard to spot unless closer to ground level!) and can be as big as a couple of metres long, stretching up the tree trunk.

    • Fallen nests and hairs:

the caterpillars can actually eject their hairs, and these can be dangerous to touch for years after they’ve fallen. Often found underneath oak trees, they can also be blown further afield by the wind.

    • Silky trails:

when the caterpillars process down the tree trunk in search of food, they’ll often leave behind a silky trail of pheromones.

    • Skeletons of leaves and bare branches:

processionary caterpillars feed on the leaves of oak trees or the needles of pines, so another tell-tale sign of a nearby population of these hungry caterpillars is dead-looking, leafless tree branches, particularly on oak trees. The Forestry Commission has plenty of useful information on their website on how to spot oaks.

Take a look at some of the signs of these nasty creepy-crawlies in this Forestry Commission video.

What to do if you spot processionary caterpillars or their nest

The most important thing is to not go near them. Keep your children, dogs and other pets away from trees you suspect might be host to processionary caterpillars and their nests.

If you live near one of the affected areas, it’s a good idea to either avoid the known sites where processionary caterpillars have been spotted (see above for a recent map), or to ensure that you can restrain or train your dog (brush up on your dog’s recall with these tips) not to go near anything that even sniffs like a processionary Caterpillar nest or infected tree. Even those caterpillars’ ejected or fallen hairs from a nearby tree or nest can be dangerous for up to five years!

If you spot a nest, for example in a tree in your garden or nearby park, please don’t attempt to remove it yourself. Instead, please report your sighting of a nest or caterpillar to The Forestry Commission – there are instructions on their website including how to identify an oak tree (if you’re unsure) and how to submit a sighting of a processionary caterpillar or nest.

What do dog owners need to know about the processionary caterpillar?

The first thing you need to know about the processionary Caterpillar as a dog owner is that they can be very dangerous. If a human comes into contact with a caterpillar or their hairs, it can cause a nasty allergic reaction, including a rash, asthma attacks, and vomiting. Dogs are at risk, too, though their symptoms may include a swollen, discoloured tongue or muzzle.

It’s important to be aware of the confirmed locations where the caterpillars and their nests have been discovered and to stay away and stay vigilant if you’re out walking your dog in areas populated by oak trees.

How do I know if my dog has had contact with the caterpillar or their hairs?

First, you should check if you live near one of the known areas where nests have been discovered. It’s important to rule out other possible causes – your vet will ask you a few question about where your dog has been recently so they can give the most appropriate treatment. Sadly, there’s no prevention treatment available as with flea prevention medicines.

Serious allergic reactions are rare and if your dog has come into contact with a few hairs it’s likely that your dog will only experience slight irritation or discomfort. In these cases, it’s a good idea to call your vet for advice and keep an eye on your dog for a few days.

However, if you know or suspect your dog has come into direct contact with a caterpillar for example by sniffing, attempting to eat or play with a caterpillar or their hairs, you may spot the following symptoms of a serious allergic reaction:

  • Swollen tongue, sometimes will appear purple-blue
  • Scratching their muzzle
  • Excessive salivation or drooling
  • Swelling in other areas such as the mouth, throat and stomach
  • Difficulty breathing or gagging
  • Vomiting

Here’s what you’ll need to do if your dog has come into contact with a processionary caterpillar:

Wash your dog’s mouth with water to reduce the effect of the caterpillar hairs – it’s important not to scrub as this will make it worse.
Take your dog to the vet for an emergency appointment. It’s important that a vet sees them quickly so your dog can be given the right treatment to alleviate the symptoms.

In the most serious and rare cases, a severe allergic reaction could be fatal, so it’s important to stay vigilant, avoid known processionary caterpillar areas and keep your dog away from oak trees where possible during the spring and summer months. After walks, make sure you check your dog’s mouth and muzzle for any signs of irritation.

Spread the word

To help get the word out about this latest outbreak and the threat it poses to dogs, share our article with dog owners you know in the south east, as well as your Rover.com dog walker. And if you don’t already have someone to look after your furry little chum, check out all of the sitters who provide dog boarding in London—it couldn’t be easier to find a dog lover who’ll treat your dog like family when you can’t be around.

Be Careful with Fuzzy and Hairy Caterpillars

Southern Flannel Moth Caterpillar (Megalopyge opercularis)

This “cute” caterpillar is the most dangerous of the three. Because of how cute it looks, children obviously want to pick it up, making it even more dangerous. Also called the puss caterpillar, asp, woolly slug, or “possum bug”, this caterpillar has venomous spines hidden in the hairs (setae) on its body. When picked up, these spines deliver a powerful and painful sting. The venom can cause searing, throbbing pain, burning and sometimes a rash with red spots. Some folks experience swelling, nausea, abdominal pain, headache, even shock and respiratory distress. They are found around quite a few species of shade trees, ornamental shrubs, fruit trees, etc. that are most often associated with schools, homes, and other landscaping plants.

As with any sting, results and symptoms depend on the individual, but some may experience allergic reactions as with bee and wasp stings, and medical attention is required.

Please be aware of children playing around flowering shrubs, fruit trees, etc. and note that stings are not always the result of a bee, yellow jacket, or hornet and could be a caterpillar. While a child or adult may not be allergic to bees and wasps, they may have an allergic reaction to caterpillar stings. Talk to your children and make sure they know that just because a caterpillar may look cute, furry, or fuzzy, they should not be picked up or touched.

It’s okay to be curious and observe these eyespots creatures, but a good rule to remember is do not touch or pick up any caterpillars, especially fuzzy or hairy ones.

The Gypsy Moths

John Frankenheimer’s “The Gypsy Moths” is not a successful movie but is neither a bad one. He goes about telling his story in the right way, but all the same he doesn’t pull it off. I found the same difficulty with his last film, “The Fixer,” which plied all the right emotions and was directed and acted with intelligence — but which never really made us care.

The challenge in “The Gypsy Moths” is to imply (without ever being so crass as to say aloud) what a skydiver’s reasons might be for jumping out of an airplane and letting himself fall right into the ground. He isn’t necessarily committing suicide; he may be in the grip of some kind of self-hypnosis, a fascination with the ground rushing up toward him.

Frankenheimer rises to this problem admirably, and he provides an exciting conclusion when the skydiver’s buddy tries to repeat the dangerous, hypnotic stunt. But somehow the rhythm of the movie has gone wrong, and at the end we’re just watching well-photographed tricks. We don’t care about the characters performing them.

That’s a shame, because earlier in the movie we do care. The story (based rather literally on James Drought’s novel) concerns a trio of barnstorming skydivers who arrive one day at a town where one of them has some relatives. The trio is led by Gene Hackman as a business-minded manager. It also includes Burt Lancaster, the hero (of course), who broods and doesn’t talk much. Scott Wilson, last seen as one of the murderers in “In Cold Blood,” is the kid with the relatives.

Frankenheimer does a good job of sketching in the atmosphere of the small Midwestern town they’re visiting. It has green lawns, frame houses with porches, and a high school band. The performances by Hackman and Wilson fit right into this community; Hackman (who played Clyde’s brother in “Bonnie and Clyde”) is particularly good at capturing the speech rhythms of an unhurried man. Lancaster’s character is aloof, just as he was in the novel. He has some sort of shadowy past that’s filled, we suspect, with hang-ups.

On the night before the big show, Lancaster has a brief affair with the kid’s aunt (Deborah Kerr). Hackman employs the town prostitute (Sheree North). And Wilson and a young girl listen to the radio news. The relationships sketched here are supposed to explain what happens the next day. And they do, more or less. The problem is that Frankenheimer then includes so much stunt footage that by the time the moment of crisis arrives, we’ve forgotten about the night before.

For all that, “The Gypsy Moths” has its moments. The aerial photography, apparently done by other skydivers, is as good as the racing footage in Frankenheimer’s “Grand Prix.” He has a knack for getting the feel of a sport. There are aerial shots in this one that may even give you vertigo, as the camera plunges toward Earth at 100 miles an hour. If only the movie itself would move a little faster.

Gypsy moth

Gypsy moth, (Lymantria dispar), lepidopteran that is a serious pest of both deciduous and evergreen trees.

The European strain was accidentally introduced into eastern North America about 1869, and by 1889 it had become a serious pest of deciduous forests and fruit trees. By the end of the 20th century the moth had spread to the western Great Lakes region. Damage is less severe in its original European range, where the moth has several natural enemies.

The heavy-bodied, flightless female moth is white with black zigzag markings and has a wingspan of 38 to 50 mm (1.5 to 2 inches). The smaller, darker male is a strong flier. Eggs deposited in clusters during July are covered with a mass of buff-coloured hair from the female’s abdomen. They hatch the following spring. The flat, pale brown larvae, with tufts of stiff brown and yellow hairs on their sides, grow to 50 mm and are voracious feeders. They often completely strip trees of their leaves in several weeks. Unlike most butterflies and moths, the larvae are the main dispersal stage. Small larvae spin silk from glands in their mouthparts and hang from branches high up in trees. If the silk lines are long enough, the wind breaks them from the tree, and the silk acts as a parasail, carrying the young larvae to new, uninfested trees to feed. When larval development is complete, they crawl down the tree trunk, settle in leaf litter at the base of the tree, and enter the pupal stage. The adult moth emerges from the cocoon after about 10 days, completing the annual generation.

A larger strain, the Asian gypsy moth, has a wingspan of about 90 mm. It poses an even greater threat than its European relative because the female can fly, enabling it to spread quickly, and the larvae, which range in colour from light to dark brown, will eat the leaves of coniferous as well as deciduous trees. It has defoliated millions of hectares of trees in Russia and China and was discovered in northwestern North America in 1991. Spraying of young larvae with either traditional or biological insecticides remains the most effective means of controlling gypsy moths.

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Gypsy Moths

© Bugwood.org

The gypsy moth, native to Europe and Asia, is an invasive moth that defoliates hundreds of acres of forests from New England west to Michigan and south to Virginia, and also on the west coast from California to British Columbia.

It was introduced to the United States in 1869 when French artist, astronomer, and amateur entomologist Leopold Trouvelot imported some eggs of this species to Medford, Massachusetts, with the idea of breeding a silk-spinning caterpillar that was more resistant to disease than the domesticated silkworm. Unfortunately, the caterpillars escaped into his backyard. About 10 years later, they began to appear in large swarms, and by the late 1880s they were causing severe defoliation in the area.

Identification

The gypsy moth caterpillar and the eastern tent caterpillar are often confused, but are readily distinguished by comparing the markings of the two species.

The gypsy moth caterpillar has five pairs of bluish warts followed by six rows of red warts running down the length of its back; the eastern tent caterpillar has no warts but a prominent yellowish-white center stripe above. (The latter also has intricate markings in blue, orange, and white and is actually quite beautiful). Tent caterpillars hatch early (about mid-April) and become conspicuous by May when they begin spinning the silken “tents” for shelter. Gypsy moth larvae, on the other hand, are just beginning to emerge by May and are tiny and inconspicuous at that time.

Life Cycle

© Bugwood.org

Like all insects, gypsy moths go through a series of distinct life stages: egg, caterpillar or larva (which changes in appearance as it grows), pupa, and adult moth.

Hatching in May from buff-colored egg masses deposited on tree trunks or in more sheltered places, the tiny (quarter-inch-long) caterpillars almost immediately climb upward toward sunlight and the leaves on which they will begin to feed.

Many of them then spin long silken threads on which they drop down from the foliage. The wind then helps disperse them to other trees, resulting in redistribution of the larvae. Once the caterpillars find a suitable tree (oak, birch, and apple trees are favorites), they begin eating the leaves, growing rapidly, and molting their skins to accommodate their increasing size.

After a few molts, the one-inch-long larvae avoid light by descending from their host tree just before daybreak and spending the day in dry, dark, sheltered spots under loose bark on trees, in leaf litter below trees, or on the undersides of objects such as picnic tables. At dusk they follow their silk thread and climb back up to the tree’s crown to feed. It is at this stage that people usually begin to notice the caterpillars and the defoliation of trees.

After passing through five or six larval stages, the caterpillars ultimately reach a length of 1.5-2.5”. In July they pupate in sheltered locations, such as the undersides of tree limbs and lawn furniture, or inside the wheel wells of parked automobiles. After about two weeks the adult moths emerge.

The flightless white-and-buff female moth gives off a chemical scent called a pheromone, which acts as an attractant to the smaller brown-colored males. After mating in July or August, each female deposits an egg mass of 75 to 1,000 eggs (mixed with yellowish hairs from her abdomen) on a tree trunk or other surface. The moths die after reproducing, but the egg masses survive the winter and renew the cycle in the spring.

Situations and Solutions

© Bugwood.org

Gypsy moths belong to the widespread family of tussock moths, some of which show cyclical population booms and crashes. During a boom, or outbreak, they can cause massive defoliation most likely in uniform stands of tree species, particularly oaks.

While a disheartening sight, the long-term effect of the phenomenon is not as disastrous as some commonly assume and may in some ways be beneficial. Thinning of forests by gypsy moths may produce a healthier, more diverse, and perhaps a more gypsy-moth resistant stand of trees.

Moderate defoliation benefits forest wildlife by stimulating understory growth of shrubs and berry-producing thickets. The larval droppings (frass) fertilize the soil, the larvae provide food for birds and mammals, and the skeletal remains of trees that succumb provide habitat for wildlife, thus promoting diversity in the forest ecosystem.

Yet, it might be comforting to know that there are some natural controls at work as well as some prevention techniques you can employ.

Natural Controls

Some native birds, such as cuckoos, downy woodpeckers, gray catbirds, and common grackles, will eat gypsy moth caterpillars but, unfortunately, not in large enough quantities to have an effect during an outbreak.

White-footed mice, and occasionally gray squirrels, prey on gypsy moth larvae and pupae. In addition, there are a number of wasps and flies that parasitize the eggs, larvae, and pupae of the moth. There are also bacterial and mold parasites that attack this moth species.

Several insect and disease controls have also been introduced. The insect predators that were brought here to function as biological controls on gypsy moth populations prey exclusively on these moths or other closely related species.

One such insect control is a large, green, predacious beetle (Calosoma sycophanta). The adult of this beetle eats gypsy moth larvae, and the larval beetles seek out and feed on the moth pupae.

Prevention

Inspect Your Yard

© Bugwood,org

In the fall and winter, inspect your property, including woodpiles, stone walls, and lawn furniture for egg masses. To kill them, scrape the eggs into a container and douse them with boiling water, being careful to avoid skin contact. Do not merely scrape the eggs onto the ground. They can survive temperatures 20 to 30 degrees below zero Fahrenheit.

Check Your Car

Egg masses deposited in the wheel wells of cars or among stacked woodpiles may account for much of the spread of gypsy moths from state to state. You can avoid carrying the moths to new areas by checking for, and removing, egg masses before leaving an infested area.

Target Trees

It may be possible to protect individual “specimen trees”, e.g. in your yard.

  • Wrapping tree trunks with aluminum foil covered in a sticky substance, recommended by some sources, has proven to be ineffective and is not good for the health of the trees; you may entrap large numbers of caterpillars, but not nearly enough to curtail the damage.
  • Wrapping trees with burlap folded over a cord to entrap caterpillars seeking shelter during the day is also ineffective due to the scope of the problem.
  • If you detect infestation of a favorite yard tree early on when the caterpillars are still small you could consider contacting a reputable pest management firm or arborist for advice.
  • If spraying of pesticides is recommended, make sure the treatment uses B.t. kurtstaki (Bacillus thuringiensis kurtstaki), a bacterial pesticide that has proven effective in killing young caterpillars of a number of pest species. Unfortunately, it can also kill many of our native butterflies and moths, the vast majority of which are either harmless or beneficial. For B.t. to be effective, it must be applied to the surface of the leaves once they have expanded for the caterpillars to ingest it, i.e. after much damage has already been done within the leaf buds. Also, the mature caterpillars feeding on expanded leaves may be resistant to the bacillus.

Plant Less Favored Trees

When choosing new plants, try to select species less favored by gypsy moth caterpillars. Ash, locust, dogwood, sycamore, balsam fir, mountain laurel, and rhododendron are less susceptible to the gypsy moth.

What Not to Do

Do not use chemical pesticides. Despite extensive control programs using various insecticides – first DDT, now mainly carbaryl (Sevin) – the gypsy moth has steadily increased its range. Although these substances do kill the larvae and thereby protect the foliage in the year of application, the insects are never totally eliminated. Furthermore, insecticides also kill the insect predators and parasites of gypsy moths and interfere with other natural controls such as the virus that kills the caterpillars at high population densities. Applications of carbaryl or other pesticides may actually prolong or exacerbate outbreaks.

Gathering and destroying the caterpillars by hand is a waste of time and effort. You will lose because you will be greatly outnumbered by larvae.

Traps to catch and eliminate the gypsy moth chiefly benefit the seller. Traps are sometimes used by scientists to count numbers of larvae and predict outbreaks. Disparlure, a synthetic chemical that mimics the sex attractant of female gypsy moths, is used to lure male moths into traps. This will not control outbreaks, however, because there is no hope of trapping enough males to prevent females from mating.

Allergic Reactions

For those who may be allergic to gypsy moth caterpillars, you should minimize contact with the insect by wearing long-sleeved shirts and by drying clothes indoors during an outbreak. Wear gloves and protect exposed skin from the egg masses while removing them.

Should you develop a rash, apply cold compresses and calamine lotion to the affected area. Hydrocortisone cream may also be used, but the rash usually goes away after two to three days without any treatment.

Updated July 2016

Gypsy Moth [fact sheet]

A well-managed woodlot is resilient to gypsy moth and other insect infestations. Do not wait for an insect outbreak—start caring for your woodlot today by contacting your local County Extension Forester. Visit www.nhwoods.org for a listing.

Impractical Control Measures for Woodlots: Several control measures are impractical for woodlots:

  • Tree Bands – Using tree bands to capture caterpillars may be of some value to an isolated urban tree with low level populations. This technique in a forest situation is useless, as it is impractical to band every tree and only a very small percentage of the larvae would be caught. Many of the petroleum-based sticky products used to repel or capture larvae are in fact harmful to trees and should not be placed on the bark.
  • Scraping or Poisoning Egg Masses – In a forest situation, a landowner cannot scrape off or poison enough egg masses to make any practical difference, as most egg masses are in tree crowns or hidden where they cannot be reached. Creosote was once used to paint egg masses but it is now a pesticide restricted by the Environmental Protection Agency (EPA) and by the New Hampshire Department of Agriculture; it is illegal to use for that purpose.
  • Fertilizing – Fertilizing forest trees is a somewhat controversial issue. It may be beneficial for individual shade tree vigor. However, the expense and logistical problems render fertilization of forest stands impractical. Furthermore, research on forest tree fertilization is inconclusive, so we cannot currently recommend the practice.

Stop! Read the label on every pesticide container each time before using the material. Pesticides must be applied only as directed on the label to be in compliance with the law. Contact the Division of Pesticide Control at (603) 271-3550 to check registration status. Dispose of empty containers safely, according to New Hampshire regulations.

Acknowledgements

The author expresses appreciation to Northam Parr, UNH Cooperative Extension Grafton County Forest Resources Educator, for his review of silvicultural techniques. He also thanks the NH Forest Pest Advisory Group for helpful comments. The Forest Pest Advisory Group is a multi-agency working committee made up of the Division of Forests and Lands (Department of Resources and Economic Development), Division of Plant Industry (New Hampshire Department of Agriculture), Audubon Society of New Hampshire, US Forest Service and UNH Cooperative Extension. This group advises State officials on forest pest conditions.

Download the resource to see the complete fact sheet.

Gypsy Moth

Related Research

The Gypsy Moth, Lymantria dispar (L.)

The gypsy moth (GM) is an invasive nonnative insect with larvae that feed voraciously on the foliage of many North American plants. GM caterpillars prefer oaks and aspens, but do not eat conifer needles unless they are starving. Preferred hosts are concentrated in the Northeast, Midwest, and southern Appalachians and Ozarks. GM was introduced about 130 years ago near Boston and has chomped its way through New England and Mid-Atlantic regions; the current “invasion front” stretches from North Carolina across to Minnesota.

At the invasion front, trees are being attacked for the first time and are usually completely defoliated, sometimes for a second time if they re-foliate. Behind the front, GM live at various densities, and populations can quickly increase (or “erupt”) every 5 to 10 years. Defoliation reduces trees’ growth, vigor, and resistance to biotic and abiotic stressors and cause direct mortality. Although less than 20% of the trees in most forests will die, tree mortality can be heavy in some places. Tree mortality reduces timber value; residential costs are associated with GM defoliation and nuisance— caterpillar hairs cause allergic reactions in humans and caterpillar “frass” (essentially excrement) can literally rain down from trees.

Fortunately, in forests behind the invasion front, several of the biological controls that were introduced at various times generally keep GM populations at reasonable numbers, although outbreaks do occur. Chemical insecticides are no longer used for spraying, only biocontrol agents such as the lepidoptera-specific bacterium Bacillus thuringiensis (Bt); a viral pathogen (Gypchek); and mating disrupters are now mostly used. For over 100+ years, the GM has been the focus of intensive study as federal, state, and academic entomologists, ecologists, and other scientists have worked to control and understand this voracious pest and stop its spread.

Much of the biology and behavior of GM has been studied and reported in the scientific literature and many control measures have been developed; they will be discussed in the sections below. Currently, Northern Research Station research focuses on newer goals — (1) slowing the spread of this insect into new susceptible habitats; (2) developing and improving biological controls; and (3) determining what factors influence eruptions or outbreaks.

Our Research

  • Risk, Detection, and Spread
  • Biology, Ecology, and Dynamics
  • Control and Management
  • Effects and Impacts

Last Modified: August 17, 2015

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