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Spongy Moth (Formerly Known as Gypsy Moth)

What Does a Spongy Moth Look Like?

The Caterpillars ~ Spongy Moth caterpillars hatch when the weather warms and the leaves open on the trees. When the caterpillars emerge they find their way to leaves and begin to eat . . . and eat . . . and eat. They satisfy their appetite mainly at night. The caterpillars grow by molting, five times for males, six for females. The feeding frenzy takes place between each molt and their appetite will increase as their size increases. They also change their appearance as they grow. When they first hatch, they are black or brown and about 1/4 inch long. As they grow, bumps develop along their back with course black hairs. There are 11 sections to a developed caterpillar and they will have two colored spots in each section. The first five sections are blue, the last six sections are red. They are about 2 1/2 inches long.

The Pupae ~ In early to mid-July, the caterpillars stop feeding and find a protective resting spot under a loose flap of bark, a flat sign nailed to a tree or the underside of some branches. Once the caterpillar chooses a space it will weave a silk net around itself and transform into a pupae. In about 2 weeks the cycle begins again with an adult Spongy Moth!

The Adult Moths ~ After emerging from the pupae stage late in July, the Spongy moth exists only to reproduce. The females can't fly, so to attract the male moths they give off a powerful scent called pheromone. The female moths are a creamy white and her wingspan is about 2 inches. The male moth, which does fly, is smaller and is colored a mottled brown. Both moths have an inverted black "V" on their wings called a Chevron. After mating the female lays the egg mass wrapped in her own hair, which can hold from 500 to 1,500 caterpillars. The egg masses are about 1 1/2 inches long, shaped like a teardrop and appear to look like tan felt.

The Egg Mass ~ The egg mass is around for nearly nine months before hatching in mid-May to early June. The are about 1 1/2 inches long, shaped like a teardrop and appear to look like tan felt. Inside the egg mass each egg develops into a tiny caterpillar. They can easily survive the winter in sheltered spots warmed by the blanket of hair and living on stored body fat. For every egg mass that is readily noticeable, there are dozens or hundreds hidden. One of the strangest places egg masses were hiding in Marinette County was inside a pair of rubber boots someone left by the back door! Usually the female lays the egg mass on the rough bark at the base of a tree, but can be found on woodpiles, lawn furniture, trailers, decks and cars.

Where are they from and how did they get to America?
The Spongy Moth is native to most of Europe and Asia. They have only been in America for about 135 yars. In 1868 a French scientist named Etienne Leopold Trouvelot brought the first Spongy Moths to America. He had left France in 1852 during the coup d' etat and settled in Medford, Massachusetts, a suburb of Boston. He had an amateur interest in entomology. His main interest was identifying silkworms and silk production. The exact reason he brought Gypsy Moths to America is uncertain, but it is believed he was attempting to crossbreed them with silkworms to make a stronger worm for silk production.

He was cultivating the Spongy Moths on some trees in his backyard behind his house when some of the caterpillars escaped. Trouvelot fully understood what could happen with the caterpiallars on the loose and warned the local entomologists but they didn't take any action. The Spongy Moths found the environment in America to their liking with a huge food supply and no real natural enemies. Shortly after the accidental escaping of the moths, Trouvelot lost interest in entomology and turned to astrology. In 1882 he returned to France to live, which ironically coincided with the first Spongy Moth outbreak in his old neighborhood of Medford.

How does the Spongy Moth spread?
The Spongy Moths greatest ability to travel is as an egg mass. The female moth deposits the egg masses on trees, houses, outdoor equipment, cars, trucks, travel trailers, and campers. Very often the egg masses have traveled hundreds of miles before hatching and starting a new infestation in the spring in a different locality.

Soon after hatching the tiny Spongy Moth larvae have the ability to travel short distances. They instinctively move up the tree towards the top and tips of the branches. There they will go "ballooning". This is where the young caterpillars suspend themselves on a silk thread. With very little body weight and long hairs to catch the wind, they float through the air, sometimes for miles before landing at a new location.

What are the Spongy Moth's favorite trees?
In Marinette County, the trees the Spongy Moth caterpillar will attack are varied. The egg masses have been found on Maple, White Pine, Red Pine, Spruce, Balsam, Scots Pine, and even Cedar. Some of the oddest places the egg masses were found were on Maple leaves, in a pair of old boots on a back porch, ferns and cattails.

The preferred trees of taste for the Spongy Moth are the Oak, Willow, Aspen (poplar), Apple and Basswood. Although these are the trees the Spongy Moth prefers - it will eat the leaves of more than 500 kinds of shrubs and trees. Keep in mind that even though Maple, Pine, nut trees, Beech, Spruce and Hemlock are less inviting to the hungry Gypsy Moth caterpillar, they will be eaten if the preferred trees are unavailable.

How long does the Spongy Moth last and what are the effects on the trees?
The Spongy Moth is here to stay - only the populations will fluctuate from year to year. Outbreaks of the Spongy Moth usually last 1 to 5 years, in Oak stands an outbreak can last 2 - 5 years, then the populations will remain low for 4 - 12 years before increasing again.

Just one 2 inch caterpillar can eat leaves covering more than two square yards! Effects of defoliation usually are most severe during an initial outbreak in a newly infested area. The trees will generate a second set of leaves if more than 60% of the canopy has been eaten. This process will stress the tree and will lessen its reserves for winter. Just how many trees will die during a Spongy Moth outbreak depends on the severity and frequency of defoliation and the trees health.

Healthy trees can survive defoliation for a few years. Additional stress, such as additional defoliation (from a different source), drought, and frost injury may kill the tree. Oak trees once defoliated, may become more susceptible to attack by the Two Lined Chestnut Borer or Root Rot. Supressed, diseased and unhealthy trees may die after one year of defoliation.

Quarantine in Wisconsin
The Spongy Moth quarantine is a set of rules enforced by the USDA Animal & Plant Health Inspection Service (APHIS) and Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP). These rules are in place to protect the non-infested areas from the spread of Spongy Moth. The quarantine doesn't affect the movement of people, it just requires that people moving trees, and tree products, other outdoor articles, trucks, campers garbage cans, trailers and any other items that would be accessible to the female Spongy Moth out of the quarantined area to be checked over to make sure the articles are free of the Spongy Moth in any stage. Failure to inspect for Spongy Moth prior to movement outside of the quarantine area is a violation of USDA quarantine regulations and may result in a penalty.

A county must have several years of 10 plus males in each trap or have an established breeding population to be under quarantine. One half of the state of Wisconsin is under quarantine which includes the counties of: Adams, Brown, Calumet, Columbia, Dane, Dodge, Door, Florence, Fond du Lac, Forest, Green Lake, Jefferson, Kenosha, Kewaunee, Langlade, Lincoln, Manitowoc, Marathon, Marinette, Marquette, Menominee, Milwaukee, Oconto, Oneida, Outagamie, Ozaukee, Portage, Racine, Rock, Shawano, Sheboygan, Vilas, Walworth, Washington, Waukesha, Waupaca, Waushara, Winnebago and Wood. (This listing can change yearly).

What are some methods of controlling the Spongy Moth?
Barrier Bands ~ One very cheap and effective way to prevent the caterpillars from getting onto the tree is to apply a barrier band. Start with these early to mid-May to coincide with the Spongy Moth caterpillar stage. Barrier bands are made with duct tape and a sticky substance like Tanglefoot Treegoo or Petroleum Jelly.

Make sure the bark is dry and wrap duct tape around the tree - shiny side in, pressing the tape firmly into cracks and crevices of the bark. Do not put the sticky side onto the bark as it could ruin the protective coating of the tree upon removal. It should be srapped a few inches wide and placed on the trunk about chest high or 4 feet above the ground. Make sure that the tape is extended past the sticky goop that could harm the tree if applied directly. Put the sticky material in the center of the band, (if using Petroleum Jelly leave at least 2 inches for melting runoff). Check the barriers often to make sure they are not clogged with dirt or insects. Be sure to wear gloves while collecting the Spongy Moth caterpillars, the hair could cause irritation of the skin. Apply more sticky substance as needed to the barrier band.

Remember to remove the barrier bands in late July after the caterpillars have started the pupa stage. This will give the tree a rest from having the bands wrapped around them.

Barrier bands and/or burlap bands are good for helping the homeowner to fight against defoliation of their shade trees during an outbreak.

Burlap Bands ~ Burlap bands are another cheap and effective way to kill the Spongy Moth caterpillar. When the caterpillars reach about an inch long in mid-June, they will crawl down the trunk to hide from predators during the day. The caterpillars hide under the burlap so you can easily collect and killa lot of them.

The band is made of a strip of burlap 12 - 18 inches wide and long enough to reach around the tree. Tie a string around the center of the band - allowing for a 6 inch overhang. If you have a sticky band already on the tree, the burlap band should be placed above it.

Check the bands from early evening to about 6 p.m., using rubber gloves and/or tweezers to collect all caterpillars, pupae, adults and eggs. Be sure to wear gloves while collecting, the hair could cause irritation of the skin. Place them in a coffee can with warm soapy water. When the insects are dead, drain the water off and throw in trash. The burlap bands can be removed in August.

Egg Mass Hunting ~ You have roughly nine months of prime egg mass hunting, September through April. It is best to look for the eg masses from fall through early spring. Any egg masses you find from May through August are most likely empty, they have already hatched, but it wouldn't hurt to destroy anyway. With each egg mass you find and destroy, you are getting rid of 500 to 1,000 potential caterpiallars!

Using a putty knife, scrape the egg masses into a plastic bag or coffee can. Be sure to wear gloves while collecting, the skin can be irritated by the hairs on the egg mass. The egg masses are about 1 1/2 inches to 2 inches long, shaped like a teardrop and appear to be tan felt. They are typically laid on rough bark at the base of a tree, but can be found on woodpiles, outdoor furnitrue, trailers, cars, decks and signs that are attached to trees. Some of the strangest places that egg masses have been found in Marinette County are - inside a beer can, styrofoam cups, and inside birdhouses.

The Virus ~ There are several natural killers of Spongy Moth. One is a virus disease called Neucleopolyhederosis virus or rather NPV. This virus plays a magor role in collapsing a Spongy Moth outbreak. After contacting the virus, the caterpillars hang in an upside down V, turn a dark color and appear to melt as they decompose over the leaves and branches. NPV is always present in Spongy Moth populations, but is seldom noticed except during a major Spongy Moth outbreak. There are two different times that the disease can attack. The first one is where the adult female moth can pass the virus to some of their offspring upon laying eggs. When these young die, it spreads the virus around the tree, foliage and other areas. Older larvae may get the virus and die before pupating. NPV doesn't afect other caterpillars or moths.