ANNAPOLIS, MD (February 01, 2016) – The gypsy moth was brought to Medford, Massachusetts by amateur naturalist Leopold Trouvelot in the late 1860s. Cotton was in short supply in the aftermath of the Civil War and Trouvelot hoped to use the webbing of the gypsy moth a create a silk-like material. Unfortunately, some of the gypsy moths escaped.

Records mention that by 1880 some 400 square miles around Medford were already infested. Within another 10 years, 360 square miles of trees were defoliated, and marauding caterpillars had become a notable public nuisance. Virtually every year since, this scene has repeated itself somewhere in the expanding area of infestation. In Maryland, the first defoliation was recorded in 1980, and outbreaks continue to this day. The gypsy moth is still Maryland’s number one forest pest. For these reasons, the Maryland Invasive Species Council has selected the gypsy moth as Invader of the Month for January, 2016.

A new outbreak has started in the Mid-Atlantic Region. In 2014 New Jersey recorded about 10,000 acres of gypsy moth defoliation; in 2015, the state recorded over 100,000 acres.. Pennsylvania recorded over 700,000 acres of gypsy moth defoliation and West Virginia, over 100,000 acres. So far, Maryland has not experienced this new outbreak. In 2015 no gypsy moth suppression project took place and only 303 acres of gypsy moth defoliation were reported. However, there are over 800 acres of proposed gypsy moth suppression area so far for spring 2016. Egg mass surveys are showing increased gypsy moth populations throughout the state.

Gypsy moth, Lymantria dispar, has five to six caterpillar size stages. Generally, we notice only the last two or three stages, or instars. These late instars have dark grey segmented bodies with several sparse tufts of stiff hairs. The first five segments have pairs of blue dots; the next six segments, pairs of red ones–on the top side of each segment. This unique pattern allows the late stage caterpillars, which may be 1” to 3.5” long, to be positively identified, differentiated from any of the thousands of other American caterpillars. The large caterpillars, which do the vast majority of feeding, appear in June. At this instar stage, it is too late to spray. Suppression efforts, to be effective, must be conducted when the gypsy moth larvae are in the second to third instars, usually late April to early May in Maryland.

Caterpillars are followed by the brown teardrop-shaped pupa, secured by sparse strands of silk in protected resting areas under bark edges or tree limbs. The adult moth emerges in about a week. Males are light brown day-flying moths with feathery antennae that live for about a week. In contrast, the female moths have white wings with small black markings and light brown bodies and are much larger. The female does not fly, but remains near her pupal resting area. Adult gypsy moths do not feed. Mating typically takes place within two days after emergence and eggs are laid the same day, after which the female dies.

Eggs are laid in a rounded oval 1”x 2” mass of 1000 or more eggs. The female covers the mass with the light brown-tan hairs and scales from her body. The eggs are laid in the characteristic resting sites – the undersides of tree limbs, rocks, and objects on the ground, behind bark flaps or signs, inside crevices, and similar places on homes or any manmade object. In Maryland, the egg stage lasts from July until April or early May when a new generation of caterpillars hatch.

The gypsy moth has five traits that result in significant social and economic impacts in its new environment. First, it is a relatively large insect (with a correspondingly large appetite). Second, because the females are flightless, they disperse poorly. Third, reproductive rate is high. These three characteristics work together to produce large numbers of hungry caterpillars rapidly in an area, with defoliation of their favorite trees, the oaks, the inevitable result. This rapid increase in gypsy moth populations is causing the current outbreak in the Mid-Atlantic. A fourth characteristic, the ability to consume some 400 kinds of plants, enables the caterpillars to continue feeding on other trees after the oaks are all denuded. In times of severe defoliation, entire hillsides or mountains are virtually stripped bare. No native caterpillar species so completely strips such large areas.

However it is a fifth characteristic that is the killer – literally. Gypsy moths take about eight weeks to grow from the time they hatch in mid-April. The last instar eats more foliage than all the others combined, resulting in the most leaf damage in early- to mid-June. By that time of the season, tree leaves are fully developed, unlike younger leaves eaten by other spring-feeding caterpillars, which are easily replaced. In destroying mature leaves, gypsy moths consume significant amounts of a tree’s nutrients. June is early enough in the season, however, that trees have reaped very little return from their photosynthetic processes. The loss of the majority of their leaves stimulates many trees to refoliate, further depleting their stored nutrients. One or two such defoliation-refoliation cycles leave the trees severely weakened, if in fact they are not killed. Weak trees are more susceptible to diseases and other insects (especially, for oaks, two-lined chestnut borers). These trees often die 1-3 years after the last defoliation.

On the more hopeful side, in 1989, a new fungal disease of gypsy moths showed up in the US. This fungus, called Entomophaga maimaiga, probably arrived from Japan, which is near the ancestral home of the gypsy moth species. This disease will effectively depress gypsy moth populations in most years. This disease is density independent but is most effective with cool wet springs. This means that the average amount of damage is reduced, although outbreaks do still occur, like the current one that is plaguing the mid-Atlantic states. In 2015, New Jersey, West Virginia and Pennsylvania suffered the worst defoliation in many years. Consequently each of these states will be mounting large spray programs to protect weakened and threatened forests. These programs will conclude by June 1, 2016, before the period of heaviest caterpillar feeding, with the desired result — much reduced forest damage this year. If the spring of 2016 does not have a fungus outbreak, Maryland will join the other Mid-Atlantic States in experiencing this gypsy moth outbreak.

For more information about other Invasive Species of Concern, visit the Maryland Invasive Species Council or call the Maryland Department of Agriculture at 410-841-5920.

For more information on the Internet:

Gypsy Moth Program. Maryland Department of Agriculture

Gypsy Moth Digest. USDA Forest Service

Gypsy Moth Pest Alert. USDA Forest Service

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ANNAPOLIS, MD (December 1, 2015) – Exotic species are in the news almost daily. They can be found in our parks and even in our own backyards. Sadly, many of them are so common, most people do not realize that they do not belong here. To be invasive, an organism must have evolved somewhere other than where it's found in Maryland, have a negative impact on the environment it moves into, and have been moved, deliberately or by accident, by people.

For example, when the brown marmorated stink bug silently slipped into the U.S., it was years before it was correctly identified as an exotic species. By that time it was already becoming a pest in orchards and vineyards.

One of the first questions about most invasive species is "How did it get here?" — quickly followed by "Could it have been prevented?" The majority of invasive plant seed, disease and insect pests are accidentally introduced. How, you might ask? While the list of pathways is surprisingly long, the most common avenues are the movement of goods produced in foreign countries, travelers returning home with souvenirs, and internet sales. The U.S. Department of Agriculture (USDA) and Customs and Border Protection (CBP) work to prevent the introduction of such pests. In this month of increased holiday travel by both people and packages, the Maryland Invasive Species Council has chosen this prevention work as the topic for the December's "Invader of the Month".

Cargo is moved in large containers with products shrink-wrapped on pallets, in boxes, or simply loaded in trucks. This results in many small hiding places that insects, seeds, and snails can use to move, unbeknownst to them, all over the world. To prevent this from happening, CBP, a branch of the Department of Homeland Security, routinely inspects cargo. The searches are extensive and include examining the exterior of shipping containers for hitchhikers adhering to the undercarriage and walls. Inside the container, pallets are checked to ensure that they have been properly treated to prevent the movement of bark beetles and woodborers. Inspectors then move to the product being shipped. Flashlights, forceps and box-cutters are routinely used to open, inspect, and manipulate the products to ensure they are pest free. The final stage of an inspection is to sweep out the empty cargo container and look for any seeds or insects that were hiding in the corners.

Most people love escaping on vacation, but if you have ever traveled internationally you might recall filling out a declaration form before leaving the faraway airport to return home. Preventing the movement of pests in baggage is challenging and relies on several factors, including the declaration form. The declaration is a reminder to all passengers entering the US that bringing in certain items is prohibited. The declaration is a federal form and false claims are subject to penalty. To reinforce the urgency and in an attempt to keep people honest, CPB randomly selects passengers for screening, checks passenger lists against a database of previous violators, and walks the baggage floor with highly trained K9 units.

The last pathway of pest introduction is internet sales. The internet has drastically increased the average person's ability to buy products, knowingly or not, from foreign countries. Foreign markets are trying to meet the high demand for heirlooms and specialty varieties and non-GMO seeds for home gardeners. Small packets of seeds are easily mailed and are found only by hard work and highly trained K9 Units. Unfortunately, a recent study reports that our current biosecurity practices are not effectively preventing the trade of plant material via internet sales (Humair et al. 2015).

You can contribute to the economic and ecological safety of the US and your own backyard by being a careful and conscientious traveler and internet purchaser. Know what you're importing, where it comes from, and make sure it's legal.Given the sheer volume of cargo, baggage and mail entering the US on a daily basis, it is unrealistic to believe that every pest will be found. Pests such as the tomato leaf miner (Tuta absoluta), wheat bug (Nysius huttoni), oak ambrosia beetle (Platypus quercivorus) and Asiatic brown rot (Monilia polystroma) are known threats. Unfortunately there are hundreds of species like them that not only threaten our neighborhoods but the entire U.S. economy. In response to this ongoing threat, the US Department of Agriculture (USDA) has established several programs to eradicate, or at least mediate the impacts of, new pests. Examples of this work include recalling products found to be infested or in violation of federal regulations, conducting surveys in and around the ports where cargo first enters the US and pests are most likely to establish, and providing funding to perform trapping across the country for high risk pests.

For more information about Invasive Species of Concern in Maryland, visit the Maryland Invasive Species Council.

photos available electronically on request.

References

Humair, Franziska, Luc Humair, Fabian Kuhn and Christoph Kueffer. 2015. E-commerce trade in invasive plants. Conserv. Bio. (in press)

US Department of Homeland Security, U.S. Customs and Border Protection. CBP Form 6059B (04/14)

Additional Resources

Animal and Plant Health Inspection Service

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ELLICOTT CITY, MD (October 1, 2013). Spotted wing drosophila (SWD), Drosophila suzukii, is an invasive, destructive pest, originating from Southeast Asia. It has recently been found in Maryland infesting blackberries and raspberries. SWD’s appearance in Maryland is why the Maryland Invasive Species Council has named it the Invader of the Month.

What makes the SWD such a devastating pest is that it attacks undamaged, ripe or unripe fruit. Damage to fruit can affect marketability and crop yields.

This pest originated in Eastern Asia and was first found on the west coast of the United States in 2008. In 2010 it was found in the Mid-West, Florida, and Pennsylvania primarily in strawberry or grapes. The rapid spread through the country was most likely due to human intervention.

The adult SWD looks like many other Drosophila species (also called vinegar flies) that attack rotting fruit. Adults are small (2-3 mm) flies with red eyes and a pale brown body with black stripes on their abdomen. The most distinct trait of the adult males is a black spot towards the tip of each wing (Photo 1). Females DO NOT have these spots, but instead have a dark serrated ovipositor with 2 rows of prominent teeth that they use to cut into fruit and lay their eggs. The ovipositor can only be correctly identified by using some magnification (at least 10x). Juvenile SWD are very small clear or white maggots that are found in the fruit.

Basic traps can be made from plastic containers, drilling ¼” holes into the plastic containers on the sides so the adult flies can enter easily. Drill the holes on the sides just below the cap. A small amount of fruit vinegar such as apple cider vinegar will attract the adult flies. About an inch of liquid is enough to last about a week in most situations. The small hole size will exclude many bigger insects but realize you may pull in other small bodied insects along with the SWD. In a trial at Michigan State University it was found that traps baited with a yeast and sugar solution caught more SWD early in the season. Whichever mixer you use add a drop of two of liquid detergent to reduce the surface tension so the flies will drown in the solution. The traps should be hung in the shade, in areas where susceptible fruit is being grown. For strawberry plants hang the traps about 12” from the ground.

Weekly monitoring during the growing season is necessary to detect the first SWD activity. Check the traps weekly, and pour the liquid from the container through cheesecloth like fabric or nylon hoses to collect the insects. The captured insects will need to be slightly air dried before examination. The males have distinct spots on the wings and if your vision is 20/20 you should see this easily. A hand lens may be needed to see this for anyone with less than 20/20 vision. The female SWDs have features that are harder to distinguish. The females do not have spots on the wings.

Once adult flies are detected, fruit can be sampled using a salt solution that forces larvae out of the berries. Make a solution of 2 cups of sodium chloride (table salt) mixed in 1 gallon of water. The fruit is harvested and placed in this solution in a container. Larvae will exit the fruit and will be visible on the surface of the fruit.

You are welcome to send samples to us at the CMREC labs (11975 Homewood Road, Ellicott City, MD 21042) for identification.

For more information about Invasive Species of Concern in Maryland, visit the Maryland Invasive Species Council.

photo available electronically on request.

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ANNAPOLIS, MD (September 20, 2012) – Many people have fond memories of raising some sort of classroom “pet,” be it butterflies, frogs, fish, hermit crabs, or “regular” pets like hamsters or gerbils. Watching a plant or animal go through its entire lifecycle is incredibly fascinating and can be an invaluable experience for a child who is just getting excited about learning.

But what is growing in your classroom? Are you learning about a native species, or a foreign one? And when you’re done with your classroom pet or project, what happens?

Ideally (perhaps to the surprise of some), these organisms should either be kept by students or teachers, or humanely disposed of. What many people don’t realize is that many of the species grown in classrooms, while great for education, are bad for our Maryland ecosystem. If the species does not occur naturally, and it proliferates in the wild (as so many do), it can do great harm to the naturally occurring flora and fauna. These organisms pose special risks because the people caring for them (simply by being students and their teachers) are often not as knowledgeable about the organisms as they could be, and not prepared for the long term (i.e., the organism’s lifespan). Release into the wild after a stint in a classroom is all too common. For this reason, classroom organisms have been chosen as the Invader of the Month.

If you were to think about the pets one might raise in a classroom, what comes to mind? Butterflies are probably your first thought. Many a class has raised a caterpillar and watched it turn into a chrysalis and then a beautiful butterfly when learning about the life cycle.

In Maryland, we of course have lots of beautiful native butterflies. In fact, our state insect is the Baltimore Checker-Spot butterfly. Unfortunately this species of Maryland fauna is now fairly rare. Other natives include the monarch, the red admiral, many types of swallowtails, etc. In classroom projects, the most common butterfly to raise is the Painted Lady. This is also a native species, and is an example of something that could be safe to release into the wild. But butterflies like the Cabbage White, originally from Europe, are actually invasive, and should be avoided.

Goldfish are another common classroom pet (and are also something commonly won at fairs, by children). Those who do not want to care for them often release them into backyard ponds, lakes, and streams, where they usually thrive, as goldfish are a hardy, coldwater species of carp. We have carp here—but not this kind! Goldfish can grow to extremely large sizes given space and food. In fact, outgrowing a tank is often the reason people release them. Given a wide open pond with plenty of smaller things to eat, they can quickly take over.

Frogs are another example of this idea; if you get tadpoles, children can watch the frog slowly but surely come into its own and reach adulthood. It’s natural, after that, to want to release it and allow it to thrive as an adult. But know what you grow; non-native frogs are incredibly dangerous to an ecosystem. Imagine if someone were to release African Clawed frogs (common in gift stores) into a stream or lake—this particular frog can grow to 5 inches and is voraciously carnivorous.

You might be surprised by the kind of animals you could find in classrooms, too. I know a girl who has a pet tarantula that used to be a class pet—no tarantulas are native to Maryland, so this was the perfect “final destination” for that arachnid. People also keep stickbugs, which are awesome classroom pets, but many species of them are also parthenogenic, and could be absolutely devastating to an ecosystem if not properly contained. Even the waste from these insects has to be properly disposed of, because it could contain eggs (freeze it for a few days before throwing it out).

It’s not only animals from classrooms that can be a problem, of course. Plants are some of the worst invaders. They can spread with alarming rapidity, especially water plants. Plants such as the anacharis (elodea)-like hydrilla are popular in classrooms to use under the microscope, because they have such easily seen cells in their leaves. They are also popular in aquariums; so put your plants to use there after you’re done in the classroom, instead of in the wild! Anyone that has had anacharis in their aquarium knows how fast it can grow. Anacharis is native to North America, but hydrilla is not, and many lakes across the country are having huge problems with the spread of this water weed.

Perhaps one of the coolest, and most dangerous, classroom projects is a mini ecosystem, or terrarium. Often these have multiple organisms in them—snails on the land portion, a goldfish or guppy in the water, an aquatic plant for the fish, etc, a perfect storm. I’ve already mentioned the dangers of invasive fish and plants.

Gerbils are an active, social and interesting classroom pet. They are omnivorous, hardy and are perfect invaders. In fact, California bans possession of gerbils for fear that they would establish themselves in agricultural fields.

Keep, don’t release! Whether it’s something you acquired from school or the fair, keep it or rehome it, but don’t release it into the wild. Past science projects can make fascinating pets. If you can’t keep it, humanely dispose of it rather than release it. It’s better than disrupting our Maryland ecosystem. Most plants and insects can be safely and easily disposed of by freezing. Or you can find someone who would appreciate a new pet to care for and love. But whatever you do, don’t release non-native species into Maryland’s ecosystem. It’s not doing anyone (or anything) any favors.

For more information about Invasive Species of Concern in Maryland, visit the Maryland Invasive Species Council.

photos available electronically on request.

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ANNAPOLIS, MD (August 20, 2012) – Mile-a-minute weed, Persicaria perfoliata(L.) H. Gross, is an annual Asian vine that has invaded a variety of habitats in the northeastern and mid-Atlantic states. First discovered in southeastern Pennsylvania in the mid-1930’s, it has since spread to as many as 12 mid-Atlantic and northeastern states. Its current range extends from Pennsylvania north to Massachusetts, west to Ohio and south to North Carolina. Habitats affected include forested floodplains, streamside herbaceous wetlands, and upland forests. Backyards and landscapes can also be easily invaded. The vigorous vine, while only an annual plant, can grow as much as 15 feet in a single season, often choking out native or more desirable vegetation. Due to its sprawling growth habit, it is very difficult to control using selective sprays of herbicides without harming non-targeted vegetation. Mechanical control (i.e. hand pulling) is possible, but quite difficult and unpleasant due to the thorny nature of the vine. Even when an area is once rid of mile-a-minute weed (MAM), the seed that has fallen and remains in the soil can produce new generations of the plant for as long as seven years.

Often the best management alternative in this type of situation is to search for an herbivore (plant eater) that specifically attacks the targeted plant. This is known as biological control. A search for a biological control agent to target MAM was initiated by the U.S. Forest Service in 1996. Field surveys and laboratory host specificity tests of a number of candidate species were originally conducted in China and subsequent testing continued under quarantine conditions in Delaware. A weevil, Rhinoncomimus latipes Korotyaev, was determined to be extremely host-specific to MAM, that is, these weevils are not interested in eating anything but MAM. The adult weevils are about two millimeters long, and are black, but may be covered by an orange film derived from plant exudates once they start feeding. Adult weevils eat small holes in young leaves of MAM and lay eggs on leaves and stems. After hatching, larvae bore into the stem where they complete development, then exit the stem and drop to the soil for pupation. Development from egg to adult takes about 26 days under laboratory conditions. The adult feeding does reduce leaf area on the plant, but the real damage that can lead to plant death is caused by the larva boring in the interior of the stems. Infested stems will shrivel and die, often before any viable seed is produced.

After field and laboratory tests were completed, mass-rearing of this insect was begun at the New Jersey Department of Agriculture (NJDA) Phillip Alampi Beneficial Insects Laboratory, in Trenton, New Jersey. Original field releases were made under federal U.S. Department of Agriculture (USDA) permit in New Jersey in July 2004. Initial results were quite promising as weevils readily established on and caused significant damage to populations of MAM. The diminutive insects also proved to be able colonizers, spreading to patches of MAM weed as far as 6 miles from initial release sites in a single season.

Encouraged by this initial success, the Maryland Department of Agriculture (MDA) partnered in a cooperative effort with researchers at the University of Delaware Department of Entomology and Wildlife Biology in a MAM biological control study. MDA applied for and received a federal permit to release the weevils beginning in 2007. The first Maryland releases of the weevil were made that same year in Howard County by the MDA in partnership with the Howard County Department of Recreation and Parks. Since that time over 12,000 weevils have been released at locations in 12 counties in Maryland ranging from the eastern shore to northeastern Maryland and from southern and central Maryland to the Blue Ridge in western Maryland.

Because MDA conducts other biological control and beneficial insect rearing as part of Integrated Pest Management (IPM) programs targeting specific insect and weed pests, it began its own MAM weevil rearing program at the MDA Annapolis headquarters in 2009. Current funding for MDA’s MAM biological control program comes from USDA APHIS PPQ and from the Maryland State Highway Administration (SHA). MDA is concentrating the continuing weevil release efforts on SHA right of ways, and is trying to establish populations of the weevil at the edges of known MAM weed distribution in Maryland. Those areas are; southern Maryland, far western Maryland, and the lower Eastern Shore. The goal of the Maryland MAM weed biological control project is to have long term establishment of the weevil in all areas of the state where MAM weed occurs. If the weevils act as ideal biological control agents, and at this point all indications point in that direction, both the weed and the weevil will persist at low levels, locked in eternal combat.

For more information about Invasive Species of Concern in Maryland, visit the Maryland Invasive Species Council.

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