Gypsy Moth: All You Need to Know for Effective Management and Control

The Gypsy Moth, now referred to as the Spongy Moth, is a notable invasive species in the United States. These pests are known for their voracious appetite for trees and shrubs, causing extensive damage to forests and landscapes.

Characteristics of the Spongy Moth include:

• Distinctive fuzzy appearance
• Males are brown and have feathery antennae
• Females are white or cream-colored and have a larger body size

The impact of the Spongy Moth on the environment can be severe. For example, the moth can defoliate entire trees, affecting both the aesthetics and the overall health of the affected area. Moreover, they can threaten local biodiversity by causing the decline of certain native species.

A comparison between the Spongy Moth and a similar invasive species, the Emerald Ash Borer:

Proper understanding and management of invasive pests like Spongy Moths can help prevent significant loss and damage to our ecosystems.

Gypsy Moth Origins and Identification

European Gypsy Moth

The European Gypsy Moth (EGM) is an invasive species that was introduced in North America in 1869. Originating from Europe, it has since become a major pest in the eastern United States, attacking the foliage of mostly oak trees but also affecting more than 300 species of trees and shrubs.

Asian Gypsy Moth

Unlike the EGM, the Asian Gypsy Moth (AGM) is native to Asia and has a broader host range, targeting over 500 species of trees and shrubs. Although it is less established in North America, it is still considered a significant forest pest.

Comparison Table: EGM vs. AGM

Lymantria Dispar

Lymantria dispar is the scientific name for the gypsy moth species. Both EGM and AGM fall within this classification, with differing subspecies.

Males and Adult Females

In terms of appearance, male gypsy moths are smaller, with a wingspan of 35-40 mm. They have brownish-gray wings, while adult females have a wingspan of 50-65 mm and are predominantly white or cream-colored.

Gypsy Moth Caterpillars

Gypsy moth caterpillars hatch in April or May from eggs laying dormant during the winter Smithsonian Institution. Young caterpillars are black and hairy, and as they grow, their appearance changes to mottled gray with hair tufts and blue and red spots on their back. Caterpillars of both subspecies have similar characteristics.

Gypsy Moth Caterpillar Features:

• Hatch in April or May
• Black and hairy when young
• Mottled gray with hair tufts as they grow
• Blue and red spots on their back

Lifecycle and Reproduction

Eggs and Egg Masses

• Spongy moth (Lymantria dispar) females lay egg masses containing up to 1,000 eggs
• Commonly found on tree trunks, branches, and other surfaces
• Covered in a protective, spongy substance

Egg masses are laid in highly transient places, providing the moth good opportunities for spreading. Eggs usually hatch in April, depending on local temperatures.

Hatch and Growth Rate

The rate of which larvae grow depends on both temperature and nutrient availability. For example:

• On a warm, sunny day with abundant food, larvae can reach their next growth stage in just 3 to 4 days
• In less optimal conditions, the same growth may take up to 7 days

Pupae to Adult Transition

During early summer, usually between June and early July, spongy moth caterpillars enter the pupal stage. Some characteristics of the pupal stage include:

• Dark brown, shell-like cases
• Approximately two inches long
• Covered with hairs and found in sheltered areas, like tree bark crevices or leaf litter

Adult moths emerge from the pupae in just 10 to 14 days, marking the end of their transformation.

Comparison of Spongy Moth Growth Stages

Infestation Signs and Symptoms

Defoliation Patterns

Spongy moth infestations usually result in defoliation patterns, where certain types of trees lose foliage more severely. Some of their preferred trees include:

• Oak
• Birch
• Maple

These trees will show noticeable gaps in their foliage, and you can easily spot sylvan areas with uneven leaf coverage.

Damage to Trees

Damaged trees are another common sign of spongy moth infestations. Oak, birch, and maple trees in the northeast region may experience:

• Chewed leaves
• Small holes throughout their foliage

As a result, trees may weaken and become susceptible to other pests or diseases.

Outdoor Furniture and Items

Spongy moth caterpillars can be found on various outdoor items, including:

• Garden furniture
• Patio umbrellas
• Exterior walls

These creatures may leave behind droppings, silk, and bits of chewed leaves on your outdoor belongings, which could require cleaning or repair.

Cocoons and Larvae Presence

When spongy moth infestations are present, you may notice an increased amount of cocoons and larvae around your property, particularly on:

• Tree trunks
• Branches
• Nearby structures

Detecting a spongy moth infestation in its early stages can help minimize damage and prevent further spreading.

Preferred Tree Species and Vegetation

Hardwoods

Spongy moths, previously known as Gypsy Moths, have a preference for certain tree species. They primarily feed on hardwoods like oaks and aspens, causing significant defoliation and stress to these trees. Some examples of favored hardwoods include:

• Oak trees
• Aspen trees
• Basswood trees

Conifers

While spongy moths prefer hardwoods, they are also known to feed on conifers when other food sources are scarce. Examples of conifers they may consume:

• Pine trees
• Spruce trees
• Fir trees

Selective Feeding

Spongy moth caterpillars are selective feeders, but their diet includes over 300 species of trees and shrubs. They usually avoid a few tree species, even when starving:

• Hickory trees
• Dogwood trees
• Sycamore trees

Comparison of Spongy Moth Preferences

The preferred tree species and vegetation of spongy moths affect the health of trees, leading to defoliation and stress. Being aware of their feeding preferences can help protect your trees and shrubs from these pests.

Impact on Forests and the Environment

Tree Death and Decline

Gypsy moths can cause considerable damage to forests, resulting in tree death and decline. They feed on the leaves of over 300 species of trees and shrubs, with a strong preference for oak trees. An infested tree will eventually die due to repeated defoliation.

• Example: In some cases, multiple years of infestation can result in a mortality rate of up to 75%.

Increased Susceptibility to Other Pests and Diseases

Trees that are weakened by gypsy moths become more vulnerable to other pests and diseases. This affects their overall health, sometimes leading to tree death.

• Pros of gypsy moth management strategies: Biological, cultural, manual, and chemical control methods help reduce moth populations and limit damage.
• Cons: Overusing chemical controls may harm beneficial insects and lead to environmental concerns.

Effects on Biodiversity

Gypsy moth infestations can also impact forest biodiversity, as they particularly target cedar trees and other native species.

• Example: A decline in cedar tree population could disrupt the habitat of species that depend on it, such as birds and small mammals.

Comparison Table: Gypsy Moths vs. Drought

Methods of Control and Prevention

Biological Control Agents

• Bacillus thuringiensis kurstaki (Btk): A soil-dwelling bacterium that specifically targets spongy moth caterpillars, leaving other species unaffected.

  • Pros: Highly specific, low impact to other insects
  • Cons: Takes time to work; becomes ineffective with rain

• Entomopathogenic fungus: This fungus attacks spongy moth caterpillars and helps control their population.

  • Pros: Natural method of control
  • Cons: May affect other insects as well

Chemical Treatments

• Pheromone traps: These lure male moths, reducing mating rates and decreasing populations.
  • Pros: Highly targeted, non-toxic
  • Cons: Doesn’t control current larvae populations
• Insecticides: Using targeted chemicals can eliminate moths by aerial spraying or direct treatment.
  • Pros: Effective in controlling large infestations
  • Cons: May be harmful to other species; potential environmental impacts

Physical Removal Techniques

• Egg mass removal: Manually scraping off egg clusters from infested surfaces.

  • Pros: Direct, cost-effective method
  • Cons: Time-consuming, not 100% effective

• Tree banding: Wrapping a sticky barrier around the trunk of a tree, trapping caterpillars attempting to climb.

  • Pros: Effective for individual trees
  • Cons: Doesn’t decrease overall moth population

Regulated Programs and Initiatives

The USDA-APHIS oversees programs on a federal level to manage spongy moth populations. Initiatives include:

• Implementing quarantines and restricting movement of infested firewood
• Monitoring and tracking the spread of moths
• Collaborating with state agencies and universities to develop better control methods

Combatting Gypsy Moths in Residential Areas

Identifying and Removing Egg Masses

Gypsy moth egg masses are typically oval-shaped and about the size of a quarter. They are covered in a tan or buff-colored fuzz. Look for these egg masses on trees, outdoor furniture, and other objects around your property. The best time to do this is in winter, when leaves have fallen and the egg masses are more visible. Once you’ve identified them, remove the egg masses using a scraper or a similar tool and submerge the masses in soapy water to kill the eggs.

Homemade Traps and Pheromone Lures

Creating a homemade trap to catch gypsy moth caterpillars is simple:

• Wrap a piece of burlap around the trunk of an infested tree.
• Tie a string or twine around the burlap to secure it.
• Once the gypsy moth caterpillars crawl under the burlap, they’ll become trapped and can be removed.

In addition, pheromone lures can be used to attract and trap male gypsy moths, preventing them from mating with females. These lures contain a synthetic version of the female gypsy moth’s sex pheromone, which attracts males. You can purchase pheromone lures online or at gardening stores, and use them in combination with sticky traps to catch the males.

Protective Tree Wrapping Techniques

Another method to protect your trees from gypsy moth caterpillars is to wrap tree trunks with a protective barrier. This can be done using a sticky material, such as Tanglefoot or petroleum jelly, applied directly on the tree trunk or by using a tree band coated with the sticky material. This barrier prevents caterpillars from climbing up trees and feeding on the foliage.

Pros:

• Effectively traps caterpillars and prevents defoliation
• Easy to apply and remove

Cons:

• Potentially messy
• May need to be reapplied frequently

To summarize, combatting gypsy moths in residential areas involves identifying and removing egg masses, using homemade traps and pheromone lures, and utilizing protective tree wrapping techniques. By following these steps and carefully monitoring your property for signs of infestation, you can protect your trees and keep gypsy moths under control.

Invasive Species Management and Legislation

Legal Restrictions and Guidelines

Spongy moth (formerly known as gypsy moth) is a highly invasive pest that can severely damage trees and shrubs. To combat this issue, there are legal regulations in place to restrict the movement of spongy moth and its egg masses. These restrictions involve:

• Prohibiting the transport of infested items like firewood and lawn equipment, which may carry spongy moth eggs.
• Ensuring the movement of outdoor items from infested areas is done with caution to prevent spreading.

Government Agencies and their Roles

Several government agencies play essential roles in spongy moth management:

• The USDA Animal and Plant Health Inspection Service (APHIS) oversees the control of invasive species like spongy moth, formulating necessary restrictions and guidelines.
• The Entomological Society of America (ESA) recently changed the gypsy moth’s common name to spongy moth, reflecting the pest’s unique spongy-textured egg masses.

Collaboration in Invasive Species Management

Effective management of invasive species, such as spongy moth, requires collaboration among various entities, including:

• Government agencies like APHIS and ESA, working together on regulations and pest-sensitive matters.
• Local communities, taking necessary precautions to prevent the spread of spongy moth and report any sightings.
• Research institutions, conducting studies on spongy moth management methods and sharing their findings with conservation agencies.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Gypsy Moth Caterpillar

unknown caterpillar
We found this 2 inch long caterpillar on our front steps yesterday. It is mostly grey with faint tan stripes and russet/orange spots where the very long hair tufts emerge. Picture 2218 is very out of focus but shows how the long hairs look like the fringes of a rug. I believe the caterpillar may be getting ready to molt or pupate as it has started to spin long spiderweb-like strands arond it’s enclosure. It might have fallen from the nearby linden tree (which just finished flowering) or come from some of the plants under the tree which include rudbeckia, hosta, creeping phlox, liatris, pansies, lavendar and purple coneflowers. We live in Southeastern Wisconsin.

This looks like the pestiferous Gypsy Moth, Porthetria dispar, to us.

Letter 2 – Gypsy Moth Caterpillar from Long Island

Subject: It can’t be a gypsy moth caterpillar!
Location: Long Island, NY, USA
May 28, 2017 5:08 am
Hi. I live on Long Island, in NY. I have scrub oak trees in the front and back of my small yard. Every year we get caterpillars that come down on silk strings and then crawl up my trees and munch on the leaves and poop on the ground. Every single person here is saying that they are gypsy moth caterpillars, and that certainly fits the description, yet nobody bothers to look at them. They do not have double dots going down their backs and none of them are blue. They have single red dots going down their backs and some tiny yellow dots in pairs and on their heads and tails.
Please, can you help me to correctly identify these caterpillars? Thank you!!!
Signature: Jenny

Hi Jenny,
Our first reaction was that they act like Gypsy Moth Caterpillars and they resemble Gypsy Moth Caterpillars, but they are different.  We then did a web search of Caterpillars and Long Island and found the Alternative Earth Care Tree & Lawn Systems site and the pictured Gypsy Moth Caterpillar looks exactly like the image you submitted.  This brings up several possibilities in our mind, and demands additional research.  First is that there is a Long Island variation on the Gypsy Moth Caterpillar and second is that perhaps this is an earlier instar than that typically shown.  Caterpillars molt five times and their appearance often changes startlingly, so different instars might appear to be different species.  The site states:  “The caterpillar larvae are about ¼” long and are black in color. As they grow they develop black hairs and colored spots and can eventually grow to 2 ½” long.”  Since it is just the end of May, the early instar possibility seems most valid as the caterpillars feed into mid-summer.  This BugGuide image appears to be a transitional phase between your individual and the more typically pictured Gypsy Moth Caterpillar.  This BugGuide image from mid May also has coloration similar to your individual, so we are convinced that your individual is indeed a Gypsy Moth Caterpillar.  Perhaps you will entertain the thought of sending us an additional image later in the summer when your caterpillars should be maturing and more closely resembling the red and blue spotted appearance generally pictured for Gypsy Moth Caterpillars?  BugGuide does state:  “‘The larval stage (caterpillar) is hairy, and a mature larva is 50-65 mm long with a yellow and black head. Behind the head on the thorax and abdomen are five pairs of blue spots (tubercles) followed by six pairs of brick red spots.'(from Penn State website) Please note: earlier instars (under about 12mm) do not exhibit the characteristic blue and brick red pairs of tubercles, nor the yellow and black head. Look instead for ‘first thoracic segment with prominent subdorsal warts bearing numerous long setae that makes face look “eared.” ‘(Caterpillars of Eastern Forests). ”

Letter 3 – Gypsy Moth Caterpillars and Pupa

Gypsy Moth Caterpillars and pupa, Cedar Point County Park, (Long Island) NY
The park is suffering from a massive gypsy moth infestation. Many trees were partially defoliated by these buggers. They invaded our campsite as well by crawling under the edge of the screen-in tent and crawling on our chairs, tables, cooler, you name it. We had to look before grabbing anything or sitting down or *squish*. Not fun. They also seem to have irritating bristly hairs, especially the larger caterpillars, which got both of us (my husband and I) in the hands as we removed offending crawlies from our belongings. I never really realized that they had such variation in color. I took a photo of a small gathering of caterpillars on a tree trunk. They are rather pretty though not great to have around. One also decided to pupate on our flag that was hanging off the tent side. The pupa had to be evicted but I was able to snap a couple of pictures of it including the size comparison one included in this email. I hope these are helpful for your site.
Tamar
p.s. Despite all of this we had a nice camping trip.

Hi Tamar,
Thank you for the partial metamorphosis documentation of the introduced, invasive Gypsy Moth, Lymantria dispar. It is a pest species throughout much of the northeast, but it has recently become established in the pacific northwest. Readers can view more images on BugGuide. We see that you sent us numerous submissions, and we will try to post what will be of most interest or assistance to our readership.

Gypsy Moth
(07/15/2008) Gypsy moth addition from Cedar Point County Park, Long Island, NY
It turns out we had a stow away after all. I found this male Gypsy moth hanging out and waiting for his wings to dry out and stiffen on one of our folding chairs (that happened to come with us on the camping trip). Maybe you can add this to my previous post so you can have photos of three stages of the life cycle of these guys.
Tamar

Hi Tamar,
We will post this adult male Gypsy Moth on our homepage and add the photo to your previous archived entry. Luckily this male Gypsy Moth won’t be expanding his range. Transportation of insects unknowingly in cars and other vehicles is one of the surest ways to expan any insects range, but this is most critical with invasive exotics like the Gypsy Moth.

Letter 4 – Gypsy Moth Pupa in Geocache

Subject: Gypsy moth pupa has taken-up residence in my geocache!
Location: Boxford State Forest, Massachusetts
July 23, 2012 7:21 pm
I was checking on one of my geocaches and found that this little guy has taken up residence in my caching container. I believe it is a Gypsy Moth Pupa. He has blurred the gps coordinates for the next stage of the cache. So, until he’s done, this stage of the cache is off-limits.
I thought you might find the photo interesting, so here it is.
Roberta 🙂
Signature: Hikingmom

Hi Roberta,
Thanks for sending us your interesting story and photo.  This might be the first Gypsy Moth Pupa we have posted so we are linking to a BugGuide photograph for comparison.  According to bugGuide, the Gypsy Moth is:  “Native to Eurasia, introduced to North America at Boston, Massachusetts circa 1869 and has been spreading ever since (US Forest Service). Michigan, Pennsylvania, and all states to the north and east of these. Also much of Wisconsin. Also the northern parts of Illinois, Indiana, and Ohio. Most of West Virginia is included in the insect’s range, as well as parts of Virginia and North Carolina. The United States Forest Service estimates the moth’s range is spreading south and west at a rate of about 21 kilometers per year. In Canada, the Gypsy Moth is present in British Columbia and in much of eastern Canada.”