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Spongy Moth


General Information

The spongy moth, Lymantria dispar dispar, (formerly European gypsy moth) is a non-native, invasive species that has moved west into Ohio from Pennsylvania and Michigan. Each egg mass a female lays contains between 500-1,000 individual eggs; once hatched they are able to feed on the leaves of over 300 different tree and shrub species. One 2-inch larvae can consume up to 1 square foot of foliage every 24 hours. In heavily infested areas, where there are 250 or more egg masses per acre, the spongy moth is able to completely strip the infested trees. A healthy tree can usually withstand only two years of defoliation before it is permanently damaged or dies. To date, 51 of Ohio's 88 counties have established populations and are under state and federal quarantine rules.

Preferred Ohio-native Tree Species
American crab apple, American hophornbeam, Bigtooth aspen, Black oak, Bur oak, Chinkapin oak, Red oak, Scarlet oak, Shumard oak, White oak, Cockspur hawthorn, Common witch-hazel, Eastern larch, Pussy willow, River burch, Smooth sumac, Staghorn sumac, Sweetgum.



Spongy moths spread in two ways, either by natural or by artificial dispersal.

Natural dispersal occurs when newly hatched caterpillars hang from tree branches on silken threads, allowing themselves to be picked up in the wind. The wind can carry them for several hundred yards to a mile, to reach another food source. This is called ballooning. As the caterpillar grows larger, their mode of transportation changes to crawling from one food source to another.

Note: Unlike other Lymantria dispar subspecies, the female spongy moth is unable to fly. The flighted spongy moth complex (FSMC, formerly known as Asian gypsy moth) are exotic pests not known to occur in the United States. FSMC moths are a regulated group of Lymantria moths and include Lymantria dispar asiatica, Lymantria dispar japonica, Lymantria albescens, Lymantria umbrosa, Lymantria postalba.

Artificial dispersal occurs when people inadvertently transport one of the life stages from an infested area on a car or recreational vehicle, lawn furniture, firewood, logs, nursery stock and other outdoor items. Before leaving an infested area, check your outdoor items to be sure you are not taking any hitch-hikers with you.


The impact spongy moth will have on a particular forest stand depends on how much defoliation occurs in the stand and how well the trees in the stand can tolerate that level of defoliation.  How much defoliation a stand experiences depends on the moth population level, tree species composition, and the quality of larval hiding places.  Egg mass counts in excess of 250 per acre generally indicate that a noticeable defoliation is imminent. Stands that contain a high proportion of preferred species are more likely to be defoliated than those with more species variability. Stands that contain numerous larval hiding places should support higher population levels, and thus experience more defoliation.

Individual tree responses to defoliation will be affected by the amount of defoliation and the tree's overall health. With broadleaf deciduous trees, light defoliation will weaken but usually not kill a tree. Heavy defoliation (> 50%) will often cause them to lose their remaining leaves and develop a second set of smaller, less efficient leaves. Weakened, less vigorous trees are more susceptible to secondary pests (insects and disease). Repeated annual defoliation will result in the death of the tree.  In contrast, conifers (pines, spruce, fir, etc.) often die as a result of the initial heavy defoliation because they are unable to produce a second set of leaves. 

Adverse Effects of Defoliation and Mortality

On People

  • Caterpillars and their feces staining homes and sidewalks.
  • Safety hazard due to dead trees and the expense of tree removal.
  • Loss of shade, causing increased heating and cooling cost.
  • Decrease property value due to loss of aesthetics.
  • Skin rashes or irritations, development of allergies in sensitive individuals because of contact with the pest.

On Environment

  • Increase tree mortality.
  • Decline in tree health.
  • Increase in fire danger.
  • Increase in stream temperatures.
  • Decrease in aquatic life.
  • Reduction in food supply for small animals (nuts).
  • Decrease in population of small animals (squirrels).
  • Reduction in food supply for some song birds.
  • Increase in nest predation of song birds due to lack of cover.
  • Increase in nesting failures of grouse and turkeys.
  • Migration of turkey and deer to non-defoliated areas.

Life Cycle 

Lymantria dispar dispar completes one life cycle (4 stages) per year.Gypsy moth life cycle


Eggs are laid in a hairy-like, brownish tan mass in late July thru early September. The size of each egg mass ranges from 1 to 1 1/2 inches in length. The number of eggs in each mass can range from 500 to 1000. They remain in this stage until April to early May. Egg masses are placed in sheltered areas of trees, buildings, fire wood, outdoor furniture, lawn equipment, and even rocks.

Images of the egg mass stage


In mid-April, tiny larvae (1/8 inch) will begin emerging from the egg masses. After emerging they begin to move up into the tree canopy and start feeding on the leaves. Larvae will molt 5-6 times before they reach adult size (2 to 2 1/2 inches). Feeding occurs during the periods between moltings (instar) and is mainly at night. Under heavy infestations feeding can go on around the clock. The larval stage is the only period in which damage is caused to the trees (leaf feeding) during the pest's life cycle. This stage lasts approximately 6 weeks.

Images of the larva stage


In early June the larvae will stop feeding, shed their skins for the last time and pupate. While in the pupa cases they transform into moths. This process usually takes about 2 weeks.

Images of the pupa stage

Adult Moth

In late June thru early July the moths emerge from the pupa cases.  Usually the males will emerge first followed by the females.  Their only mission is to mate and lay eggs. They do not feed during this stage. Since the female does not fly, she has to put out a pheromone scent to attract the males to her. Once they mate and lay their egg, the moths die. This stage lasts approximately 2 weeks.

Images of the adult moth stage


Infestation Images

The image below shows an oak tree in Marion, Ohio affected by a heavy infestation of L. dispar larvae (June 2018).
gypsy moth larvae on a tree
This image is of the same tree in Marion. Each egg mass can contain 500-100 eggs, so the population can quickly become out of control.
gypsy moth larvae on a tree
The same tree in Marion, completely defoliated by the infestation.
defoliated tree



Introduction in the United States

The introduction of spongy moth into the United States is a great example of an experiment gone extremely wrong.  Native to Europe and Asia, it was brought into Medford, Massachusetts in 1869 by E. Leopold Trouvelot, a French artist and amateur entomologist, looking to develop a new strain of silkworm for silk production. He was culturing egg masses on trees in his back yard when some larvae (caterpillars) escaped into the surrounding community. Local entomologists were notified, but no action was taken to eradicate the pest.  The first outbreak occurred on Myrtle Street, in Medford, Massachusetts in 1882.  Since the first escape, spongy moth has advanced throughout the New England states, south to North Carolina, and west through portions of the Great Lake states and Canada.

Introduction in Ohio

The first male moths were trapped in Ashtabula County in 1971. Two years later, 1973, the first chemical treatments were implemented to eradicate localized populations. Between 1973 and 1987, eradication efforts continued, but populations still grew. In 1987, Ashtabula County became the first county to have quarantine regulations imposed on it.

In 1989, the Ohio Department of Agriculture in conjunction with the USDA-Forest Service initiated the Suppression Program. This program continues today as a way for landowners in areas considered generally infested to voluntarily receive assistance in suppressing this exotic pest.

In 1998, pheromone traps were placed over the entire state of Ohio in an 8 kilometer grid system to estimate the infestation densities across the state. With this information an infestation line (where catches were >10 moths) was drawn, with the area to the east of this line being considered generally infested.

In 1999, the Slow the Spread (STS) Program was added by the USDA (Forest Service and APHIS) in Ohio as a means of monitoring the advancement and to eradicate isolated populations ahead of the infestation line. A 100 kilometer swath, paralleling the infestation line to the west was established and is referred to as the STS Action Zone. 

Monitoring and treatment projects continue today.

Name Change

In 2022 the Entomological Society of America announced a common name change for Lymantria moths, replacing the name "gypsy moth" (Lymantria dispar) with "spongy moth". ODA and USDA APHIS also replaced the common name following ESA's announcement. As the moth subspecies are regulated differently, the name "spongy moth" refers to Lymantria dispar dispar specifically. APHIS worked with its foreign partners to adopt the new common names for the other subspecies, and replaced the name "Asian gypsy moth" (L. dispar asiatica, L. dispar japonica, L. albescens, L. postalba, and L. umbrosa) with "flighted spongy moth complex."


Currently 51 counties in Ohio are regulated under the Lymantria dispar quarantine (OAC 901:5-52). Regulated articles include, but are not limited to:

  • trees and woody shrubs, including cut Christmas trees;
  • logs, pulpwood, slab-wood, firewood, and wood-bark chips;
  • outdoor household articles, including: tables, doghouses, planters, garden equipment, playhouses recreational vehicles;
  • other products or articles, or means of conveyance that may carry L. dispar  in any living stage of development.

View map of quarantined counties in Ohio

Producers who ship nursery stock out of regulated areas to non-regulated areas must have their stock inspected and each load must be accompanied by a certificate which attests to the fact that their product is free of L. dispar.  Producers, who make repeated shipments, are urged to take steps necessary to qualify for a Compliance Agreement and master certificate, otherwise they will face delays in obtaining certificates.

Compliance Agreements

Compliance Agreements are written agreements between an entity engaged in growing, selling, processing, or moving regulated articles from a regulated area and the Ohio Department of Agriculture, setting forth specified conditions to prevent the spread of L. dispar. This agreement is needed by anyone moving regulated articles out of a regulated area to a non-regulated area and anyone in a non-regulated area receiving regulated articles from a regulated area.

One main requirement for the compliance agreement is that nurseries must apply a USDA-approved insecticide to the entire growing area in mid- to late-May. For more information, contact the Plant Pest Control Section at 614-728-6400.

Inspection Certificate

An inspection certificate specifically certifies a shipment for freedom from L. dispar, allows the movement of regulated articles within the state. They can be issued by a trained staff member of any entity holding a "Compliance Agreement" or by a State or Federal Inspector.

Phytosanitary Certificates

A State Phytosanitary Certificate can be issued for individual loads of regulated articles being moved out of state, but within the continental US. This certificate can only be issued by either a State of Federal Inspector.

A Federal Phytosanitary Certificate must be issued for any regulated articles being moved out of the United States to another country. This certificate can only be issued by either a State of Federal Inspector.

Survey & Management

ODA operates an annual state-wide trapping program, and participates in three cooperative programs to manage spongy moth populations in Ohio.


Spongy moth population boundaries are estimated from moth counts in grids of pheromone-baited traps. Spongy moth populations are monitored using pheromone-baited traps. Each year in Ohio more than 10,000 traps are set before the start of the flight period in May/June and collected after flight termination in August. Potential problem areas and program boundaries are determined each year based on a line drawn along a "10 moths/trap" border.

Generally Infested Zone

This area of northern Ohio includes a portion that is not surveyed, and a monitoring zone near the 10 moth/trap line. Traps in the monitoring zone are spaced 5 - 8 km apart and are used to estimate population boundaries and for evaluating the effect of the STS program. Any treatments in this part of the state fall under the voluntary Suppression Program.

Slow the Spread Action Zone

  • The middle of Ohio is the transition area into which moths are naturally moving. Here traps are spaced 2 km and 3 km apart, which has been shown to be sufficient for detecting isolated colonies. Treatments in this area are managed by the Slow the Spread Program.
  • Delimiting grids are set in the areas that may contain isolated colonies and are spaced at either 0.5 km or 1 km.
  • Post-treatment evaluation grids are used to determine the effectiveness of treatments.

State Zone

  • The uninfested part of southern Ohio is considered the State Zone. Traps are spaced 3 km apart and isolated colonies  are controlled under the Eradication Program.

trap spacing in Ohio



Voluntary Suppression Program

Since 1989, Ohio's voluntary Suppression Program operates in the infested zone where the spongy moth population is well established and colonies overlap. The goal of the suppression program is not to eliminate the moth, but to protect trees and reduce defoliation in these areas. This program is strictly voluntary and is funded through a 50/50 cost share between the landowner(s) and the USDA Forest Service, coordinated by ODA.

Landowners may request an ODA aerial treatment by submitting an application through a local coordinator before September 1 each year. An ODA inspector will then conduct a survey to determine if treatment block meets the criteria for a suppression treatment.


  • The proposed area must contain a minimum of 50 contiguous forested acres with a tree canopy that covers no less than 50% of the block.
  • The proposed area must be in one of the 51 quarantined counties
  • There must be at least 250 egg masses per acre in residential forested areas, or 1,000 egg masses per acre in uninhabited forested areas.
  • The area must consist of at least 35% susceptible or slightly resistant tree species.
  • Finally, the proposed treatment area must receive a favorable T & E assessment from ODNR and the US F&W Service.

Once approved, cost share payment from the landowners will be due by March 1 of the treatment year. Treatment products approved for suppression include Btk, Gypchek, Diflubenzuron, and Tebufenozide and are conducted by state contracted pesticide applicators.

Click here for the Suppression Treatment Application package

Slow the Spread (STS) Program

In 1992, a spongy moth (formerly gypsy moth) Slow the Spread (STS) pilot project was initiated in Michigan, West Virginia, Virginia, and North Carolina, to reduce the rate of spread through comprehensive detection, control, and regulatory efforts. Ohio joined the STS program in 1999, which is now a national strategy funded by the Slow the Spread Foundation, the USDA Forest Service, USDA APHIS and state cooperators that lie along the leading population edge.

Each year in Ohio more than 10,000 pheromone-baited traps are set before the start of the flight period in May/June and collected after flight termination in August. The Slow the Spread project area is set on both sides from the 10 moths/trap line - 50 km in front of the line to 120 km behind the line. Potential problem areas are then identified based on the catch numbers and selected for further delineation or treatment.

Treatment options include a mating disruption pheromone, Btk, Gypchek, Diflubenzuron, and Tebufenozide and are conducted by state and federally contracted pesticide applicators.

More information about the STS program can be found at the Slow The Spread Foundation.

Eradication Program

The Eradication Program deals with isolated populations that arise beyond the transition area (120 km beyond the 10 moth/trap line) in what is considered the non-infested zone. These populations develop as a result of human movement of spongy moth life stages on infested material such as fire wood or other outdoor materials from outside the area. The objective is to eradicate these small isolated populations before they can establish themselves.

Funding for the Eradication Program comes from USDA – APHIS / PPQ and the state cooperators. Treatment options include Btk, Diflubenzuron and Tebufenozide and are conducted by state contracted pesticide applicators.

Treatment Info

Treatment Maps

aerial application of pesticidesEach summer the Ohio Department of Agriculture deploys approximately 12,000 moth traps across the state to monitor movement and evaluate, detect and delineate newly established colonies. Proposed treatment areas are determined in the fall prior to the treatment year, based on the catch numbers and the available funding between the state cooperators. Products and application rates are determined based on the catch numbers and other environmental factors.


Treatment Dates

The grid below shows the expected dates when treatments are to occur and when they were completed. Please note that treatments of individual blocks are dependent on larvae and oak leaf development and are subject to change based on weather conditions. Larvacide treatments are typically conducted during May, and mating disruption treatments occur during mid-June. Treatments that have yet to be scheduled will be listed as “To Be Announced” (TBA). 

 Area Name County Product Proposed Treatment Status
Caldwell North MD Guernsey SPLAT GM-O 6/14/2023 Proposed
Centerburg MD Knox SPLAT GM-O 6/14/2023 Proposed
Centerburg MD Morrow SPLAT GM-O 6/14/2023 Proposed
Crooksville MD Muskingum SPLAT GM-O 6/14/2023 Proposed
Fleming MD Washington SPLAT GM-O 6/14/2023 Proposed
Homer MD Knox SPLAT GM-O 6/14/2023 Proposed
Mineral MD Vinton SPLAT GM-O 6/14/2023 Proposed
Newark MD Licking SPLAT GM-O 6/14/2023 Proposed
Olive Green MD Delaware SPLAT GM-O 6/14/2023 Proposed
Ottoville MD Putnam SPLAT GM-O 6/14/2023 Proposed
Sunbury MD Delaware SPLAT GM-O 6/14/2023 Proposed

Public Session Schedule

Public information sessions (open houses) are informal meetings where people can get information about the upcoming spongy moth treatment project.

Links to the virtual open houses will become available on the Events calendar page a week prior to the session.

Online Virtual Events

Missed the meeting? Watch the recording on our YouTube channel: https://youtu.be/teAOu0i2eAw

Wednesday, February 15, 2023 6:00pm-7:00pm

Microsoft Teams Meeting (help)

Friday, February 17, 2023 12:00-1:00pm

Microsoft Teams Meeting (help)

Treatment Materials

Several pesticide products are approved for use in the USDA National Gypsy Moth Management Program, based on the 2012 final supplemental environmental impact statement (SEIS), "Gypsy Moth Management in the United States: a cooperative approach."

Foray 48B, containing Bacillus thuringiensis v. kurstaki (Btk)

Bacillus thuringiensis v. kurstaki (Btk) is a naturally occurring bacterium found in soils across the world. The insecticidal properties of Btk are specific to caterpillars of certain moths and butterflies. Btk spores and protein crystals are ingested by the caterpillar along with foliage. Enzymes in the mid-gut of the caterpillar dissolve the crystals and release delta-endotoxins, which are insecticidal crystal proteins. The proteins bind to specific receptors on the cellular lining of the mid-gut and penetrate the cell membrane. The insect stops feeding and dies within a few hours or days.

Gypchek, containing nucleopolyhedrosis virus (LdMNPV)

Gypchek is the registered trade name of an insecticide containing occlusion bodies (OB) of the Lymantria dispar nucleopolyhedrovirus (LdMNPV). LdMNPV is a naturally occurring virus that attacks specifically the Lymantria dispar caterpillar and must be ingested by it to be effective. The virus multiplies rapidly in cells of the insect and eventually causes breakdown of internal tissue and death. The entire process takes 10 - 14 days, depending on the size of the caterpillar, viral dose, and ambient temperature.

Production of Gypchek ended in 2019; remaining stocks can only be used to manage infestations by programs sponsored by the USDA Forest Service. Due to the limited availability, Gypchek is only used in areas where Threatened & Endangered lepidoptera may be affected by alternate products.

SPLAT GM-O (mating disruption)

Pheromones are chemicals produced by insects and used in communication. Disparlure is the spongy moth pheromone that attracts male moths to female moths for mating. Synthetically produced disparlure is used for both baiting traps and to interfere with spongy moth mating. By spreading the pheromone over a large area, male moths are unable to locate the female and she lays unfertilized eggs. The SPLAT GM-O product contains the synthetically produced disparlure.

Home Management

There are several practices homeowners can employ if a spongy moth infestation is found:

  • If you live in the quarantine area of the state and the area needing to be treated is 50 acres or more, then you and/or your neighbors can apply for an aerial treatment through the Suppression Program.
  • Keep your trees and shrubs healthy. Should defoliation occur, irrigate affected trees and shrubs. Adequate water will help in the recovery process. Avoid nitrogen fertilizer as they will encourage leaf growth at the expense of building food reserves in the roots.
  • Do not move outdoor lawn furniture, garden equipment, or fire wood without first inspecting the items for spongy moth life stages. If moving to a new area, check to see if you are required to follow quarantine regulations of this state or any other state.
  • Scrape egg masses and pupa cases off buildings, trees, shrubs, or any outdoor items and destroy them by submerging them in soapy water for at least two days or by burning them. Egg masses can also be killed by spraying them with a spray oil labeled for spongy moth (formerly gypsy moth).
  • Barrier bands can be placed around tree trunks to prevent larvae from climbing back onto the trees. Place a non-porous material around the tree trunk and coat it with a commercially available sticky material. Never apply the sticky material directly to the tree trunk. The larvae will become entangled in the sticky material and die. The sticky material will need to be re-applied periodically.
  • Collection bands, 12 to 18 inches wide, made of burlap, wrapped around a tree, and folded over to make a skirt attract larvae looking for shade during the day.  Each day you will need to remove and destroy the larvae.  Recently, collection band products have come onto the market that contain an insecticide in the band that kills the larvae.
  • Pheromone traps can be placed to attract the male moths and prevent them from mating with the females. Some traps contain soapy water in the bottom to kill the moths and some contain an insecticide strip.
  • Chemical treatments are most successful when applied to the foliage during the larvae's early instar stages. Trees and shrubs can be treated with a biological pesticide like Bacillus thuringgiensis (Bt) or with chemical pesticides labeled for gypsy moth. These products are available at your local garden center or nursery.