Department of Environmental Protection

New Jersey Forest Service

NJDEP LogoNJ Forest Service Logo

Forest Health Program in New Jersey

The New Jersey Forest Service (NJFS) surveys and monitors New Jersey's forests both from the ground and the air for various forest health threats. While most insects and diseases are part of the natural ecosystem, the NJFS is mainly concerned with forest health threats that are invasive, spread quickly, or can have the ability to affect otherwise healthy trees. Often the pests and diseases of concern are non-native and introduced to our forests accidentally. Without native predators, these pests have the potential to cause indiscriminate, accelerated, and widespread tree mortality.

Details
The spotted lanternfly (SLF) was detected in NJ in the summer of 2018 in Warren, Mercer, and Hunterdon Counties. Currently, SLF is detected in 19 counties.

SLF is native to China, Bangladesh, and Vietnam. The first North American detection was in Pennsylvania in 2014, and has since been detected in Virginia, Delaware, Maryland, Connecticut, West Virginia, Ohio, and New Jersey. The SLF is a leaf hopper insect that feeds on the phloem of trees and plants. The SLF excretes honeydew (a sticky, sugary waste product) onto anything that is below the insect, including plants, young trees, shrubs, sidewalks, outdoor furniture, etc. In large quantities, honeydew facilitates the growth of black sooty mold that blocks photosynthesis on trees and plants. Copious amounts of honeydew can cause dieback or tree/plant mortality. In agriculture, extensive SLF feeding also causes reduced yield in crops and black sooty mold on produce reduces their marketability.

SLF has a wide host range that includes over 70 different trees, shrubs, vines, and plants. However, it has a strong preference for the tree of heaven, also called Ailanthus altissima. . Immature SLF are often found feeding on young growth, or new branches because the tissue is softer. However, as they mature into adults, they can be found at the base of the tree or feeding on the trunk. SLF can also be found feeding on maple, black walnut, grape vines, and multiflora rose.

SLF, contrary to its name, is not a fly but in fact a type of planthopper. Although SLF are able to fly, they more often jump or glide as modes of transport. SLF most effectively spread to new areas by hitchhiking rides from infested areas. Therefore it is imperative for anyone traveling in and out of known SLF areas to check their vehicles, goods, etc., for any life stages of SLF to prevent the further spread to new areas.

Susceptible Species
Prefers the invasive “Tree of Heaven,” but makes use of over 70 different plant species including fruit trees, ornamental trees, woody trees, vegetables, herbs, vines, and agricultural crops

Signs of Infestation
Any life stage of the insect is visible feeding on plants, sooty mold, heightened activity from wasps, hornets, ants, and bees

Affected Areas
Atlantic, Bergen, Burlington*, Camden*, Cumberland, Essex, Gloucester*, Hudson, Hunterdon*, Mercer*, Middlesex, Monmouth, Morris, Passaic, Salem*, Somerset*, Sussex, Union, and Warren* Counties

*Counties under State Quarantine

More information

Details
Beech leaf disease (BLD) was confirmed in New Jersey in the summer of 2020 in Bergen and Essex Counties.

BLD was first detected in North America in Northeast Ohio in 2012. This was a mysterious disease that could not be identified. However, in July 2020, researchers discovered a nematode associated with BLD. The nematode, Litylenchus crenatae mccannii, damages leaf tissue, which causes leaf discoloration and eventual leaf and bud necrosis. After several years of infection, defoliation, dieback, and eventual tree mortality occurs. Smaller, understory beech trees appear to be the most susceptible, succumbing to BLD within 1-5 years, and larger, overstory beech trees succumbing within 6-10 years. BLD has been spreading rapidly since its initial detection in 2012, has since been detected in Pennsylvania, New York, New Jersey, Connecticut, Rhode Island, West Virginia, Massachusetts, and Ontario, Canada.

Researchers and scientists are still learning about BLD, and so there is currently no cure or treatment for BLD. However, reporting new detections can help better understand its most current distribution and track the BLD progression and movement. If you suspect BLD, please contact the NJFS Forest Health Program at foresthealth@dep.nj.gov or 609-292-2532.

Susceptible Species
American, European, and Oriental Beech

Signs of Infestation
Dark banding on the leaves visible on green and brown leaves, leaf edges can start to curl and become leathery in texture, leaf necrosis, thinning crown from the bottom up.

Affected Areas
Bergen, Essex, Hunterdon, Mercer, Monmouth, Morris, Passaic, Somerset, Sussex, Union, and Warren Counties.

More information

Details
Southern pine beetle (SPB) is considered a native insect in New Jersey and was reported as causing damage in southern New Jersey in December 2001. SPB is often present in endemic (low) levels, successfully attacking weakened and stressed pine trees. However, there are also times when SPB populations reach epidemic (high) levels and they are able to successfully attack healthy pine trees. When SPB populations reach epidemic levels, they have the ability to cause significant damage across its range. It is one of the only native bark beetles that can attack healthy trees, where the adult beetles cut off water and nutrient supplies to trees by boring through the bark and creating S-shaped galleries in which they lay their eggs.

The historic native range of SPB includes the southeastern US and parts of Central America, but over the last decade, SPB populations have started to move north. In 2014, SPB populations were found in Long Island, NY causing extensive pine mortality. Through insect trapping, SPB have been detected in Connecticut, Rhode Island, and Massachusetts, the furthest north of its range in history.

Preventing SPB populations from reaching epidemic levels is the most effective method at prohibiting widespread SPB induced tree mortality. Some prevention actions include:

  • Continual monitoring and surveying of SPB activity and suppressing SPB spots while small to prevent larger SPB outbreaks.
  • Removing weakened and stressed trees that serve as the initial breeding sites for SPB can also prevent SPB populations from establishing.
  • Maintaining healthy pine stands that are better able to defend themselves from SPB attack
  • Encouraging or planting appropriate pine species for the site, so growing the “right tree in the right spot”

Susceptible Species
SPB attacks all species of pine including pitch, shortleaf, Virginia, white, loblolly, and red. To a lesser extent, SPB can attack Norway Spruce, red spruce, and Eastern hemlock.

Signs of Infestation
Pitch tubes, exit holes, yellow and browning crowns, S-shaped galleries under bark

Affected Areas
The southern half of the state has been affected by SPB, however SPB have been detected in traps statewide

More information

Details
LDD was first discovered in New Jersey in 1920 and continues to be present in the environment. Fortunately, annual monitoring, suppression programs, and several established biological controls help keep gypsy moth populations in check.

The LDD is native to Europe and was introduced to North America in 1869 in Massachusetts by a scientist, E. Leopold Trouvelot, who was hoping to use LDD caterpillars for silk production. The caterpillars accidentally escaped his property and soon began spreading and infesting surrounding areas. LDD is currently established from Maine to Virginia and as far west as Wisconsin and Minnesota.

The LDD larva causes the most destruction, feeding on leaves from over 500 different species of trees and plants. The larvae feed on leaves from May to June, and although healthy trees can survive a single year of defoliation, several successive years of heavy defoliation can result in tree decline and mortality. The LDD population in New Jersey is influenced by the presence of the biological controls, Entomophaga maimaiga and Nucleopolyhedrosis virus (NPV). E. maimaiga is a fungus that infects and kills gypsy moth caterpillars, thriving during wet years. NPV is a naturally occurring virus that is most effectively transmitted between caterpillars when LDD populations are high. Although there are additional natural controls that feed on gypsy moth, E. maimaiga and NPV are specific to LDD and are the most effective at impacting LDD populations.

LDD populations are generally cyclic, peaking every 5-10 years, and are able to increase more rapidly during dry years when E. maimaiga is scarce. In 1981, New Jersey suffered the worst LDD defoliation, impacting over 800,000 acres. Although LDD populations eventually started to decline, populations began to increase again in 2005 – 2007, increasing from 42,000 acres to 324,000 acres respectively. Suppression programs are in place to supplement natural controls during peak LDD years in order to prevent another devastating LDD defoliation event, like the one that took place in 1981. Currently LDD populations are low, but are monitored annually to track their population trends.

Susceptible Species
Prefers oaks and but also attacks many deciduous trees and shrubs

Signs of Infestation
Presence of any life stage of the LDD (adult moth, caterpillar, or egg mass), defoliation, oval egg masses, caterpillars

Affected Areas
Statewide

More information

Details
Hemlock woolly adelgid (HWA) was detected in NJ in 1978 in Burlington County and is currently found statewide. The heaviest of HWA infestation occurred in the mid to late 1990’s, causing widespread hemlock mortality, and destroying the majestic hemlock forests that once existed along streambanks and hillsides. The impacts of this outbreak are still evident today, where hardwood species have filled in where hemlock forests once existed. Today, individual surviving hemlock trees, or small groups, can still be found scattered across the landscape, and it is hopeful that these will serve as the seed source for future hemlock forests. Nearly all hemlock in New Jersey, approximately 25,000 acres, have been infested with HWA to some extent.

HWA is native to east Asia, and was first discovered in the eastern United States in 1951 near Richmond, Virginia. HWA is a small, soft-bodied insect that feeds on the sap of young branches. In the Northeast, all HWA are females that reproduce parthenogenically. HWA has a complex life cycle, involving three generations per year. One is a winged generation that does not survive in the Northeast, presumably because the spruce host required is not available here. The two other generations are wingless and are so small they are difficult to see with the naked eye. It is the third generation that develops a white, cottony covering, that makes them more visible on the underside of hemlock branches during the late fall and winter.

Starting in 1998, biological controls have been released to help control HWA populations, starting in 1998. These predacious insects include Sasajiscymnus tsugae, Scymnus sinuanodulus, and the most recent, Laricobius nigrinus in 2005. Cold winter temperatures, pesticide treatments, and host tolerance, also contribute to help protect hemlock trees from HWA infestation.

Susceptible Species
Eastern hemlock

Signs of Infestation
Small white woolly cotton-like balls on the underside of hemlock branches, branch dieback, crown thinning

Affected Areas
Statewide

More information

Details
After overwintering in the soil beneath the host tree, moths emerge in May and June to lay eggs on the tree's needles. By mid-summer, the larvae hatch and eatneedles down to the sheath. When enough defoliation of host trees occur, mortality results for trees of all sizes with younger trees being most susceptible.

Susceptible Species
Pine species

Signs of Infestation
Brown needles, defoliation

Affected Areas
Ocean and Eastern Burlington Counties

Details
The emerald ash borer (EAB) was detected in NJ in 2014 in Somerset County, and has since been confirmed in 17 counties in the state.

The EAB is native to Asia, and was first detected in North America in 2002 in Michigan and has since been detected in 35 US states and 5 Canadian provinces. EAB is an invasive and destructive pest, responsible for killing hundreds of millions of ash trees in the US. Adult beetles lay eggs in bark crevices, and larvae then burrow under the bark and feed on the cambium, cutting off water and nutrient transport within the tree.

Systemic pesticide treatments are effective at protecting individual trees, and should be applied by a licensed pesticide applicator. Systemic treatments are most effective when applied to healthy trees, prior to or soon after EAB infestation, so that the pesticide can be effectively circulated throughout the tree.

Biological controls that specifically feed on EAB, have also been released in the US in areas impacted by EAB. NJ started its biocontrol release program in 2016 and continues to release EAB biocontrols annually. The biocontrol insects include tiny wasps that parasitize either the EAB egg or EAB larva. Biocontrol efforts are a long-term management strategy and unfortunately, will not protect the current ash populations that exist today. Biocontrols first need to build their populations, which can take several years, and the hope is that the next generation of ash trees will be better protected from EAB infestation.

Susceptible Species
White ash, green ash, black ash, pumpkin ash

Signs of Infestation
D-shaped exit holes, woodpecker flecking on bark, larval galleries under the bark, branch and crown dieback, epicormic sprouts on trunk or base of tree

Affected Areas
Statewide

More information

Details
The Asian longhorned beetle (ALB) was detected in New Jersey in 2002 in Hudson County. In 2004, additional ALB populations were detected in Middlesex and Union Counties. However, as a result of an aggressive and successful ALB eradication program, in 2013, NJ deregulated the ALB quarantine zone, and no ALB have been detected in the state since.

The ALB is native to eastern China and Korea, and was first discovered in North America in 1996 in Brooklyn, NY. ALB has since been detected in additional locations in New York, Illinois, Ohio, Massachusetts, New Jersey, and most recently in South Carolina in 2020.

ALB feed on over a dozen different trees with their most preferred being maples, willows, ash, and poplars. The female beetles chew holes in the bark where they lay their eggs. After hatching, the young larvae feed on the cambium layer of the tree, the living tissue under the bark responsible for transporting nutrients and water throughout the tree. The larvae then bore deep into the tree where they eat and create tunnels through the tree’s heartwood. The effects of ALB feeding on trees can be seen 3-4 years after infestation with branch dieback and leaf discoloration. Infested trees will eventually die approximately 7-12 years later.

Susceptible Species
maple, willow, poplar, ash, horsechestnut/buckeye, elm, birch, golden raintree, London planetree/sycamore, katsura, mimosa, and mountain ash (Sorbus sp.)

Signs of Infestation
Adult ALB, 3/8" exit holes, oozing sap, sawdust, branch dieback

Affected Areas
Eradicated from Hudson, Union, and Middlesex Counties

More information

Details
Although the origin of sudden oak death (SOD) is still unknown, its detrimental impacts on North American oak species suggest the pathogen is non-native. SOD is a fungal pathogen that was first discovered in California in the mid-1990s and then in Oregon in 2001. SOD is responsible for the mortality of millions of coast live oak and tanoaks in California and Oregon.

SOD not only infects oak trees but can also infect shrubs such as Rhododendron sp. and Camellia sp.. In addition, there are numerous plants that are asymptomatic carries of the SOD pathogen, which also contributes to the unknown spread to susceptible hosts, such as oak trees.

Susceptible Species
75 Species including many oaks

Signs of Infestation
Brown leaves, large bleeding cankers

Affected Areas
Not yet found in NJ

More information

Details
Although bacterial leaf scorch (BLS) is considered native to NJ, it was first observed causing tree damage and mortality around 1985 in the southern half of the state, mainly affecting trees in the Red Oak family, such as Northern red oak, pin oak, and scarlet oak. Today, BLS can be found statewide, affecting landscape and street trees as well as those growing in forests.

BLS is a bacterium that is transmitted to healthy trees by leafhoppers and spittlebugs moving from asymptomatic herbaceous plants, such as goldenrod, blackberries, and clover that harbor the bacteria. BLS clogs the trees vascular system responsible for transporting water and nutrients throughout a tree. BLS infected trees will have leaves that have a scorched appearance along the leaf margin. The junction of scorched tissue and green tissue is often yellow or halo-like, one of the identifying features of BLS. In NJ, BLS leaf scorch symptoms become visible in early to mid-August, and is predominately found on red oaks, although it can be detected in other species including sweetgum, elm, and maple.

There is no cure for BLS, however, BLS is a slow tree killer, often taking 10 or more years for an infected tree to succumb but causing gradual canopy decline and dieback over that time. Although antibiotic trunk injection treatments are available to treat BLS symptoms, these treatments must be done on an annual basis and treatments are most effective when done either prior to or soon after infection.

A look-a-like is oak wilt, which has not yet been detected in NJ. See oak wilt for more information.

Susceptible Species
Red oak family (Northern red, pin, scarlet, willow, black, and Southern red), maple, sycamore, elm.

Signs of Infestation
Brown discoloration along leaf margins in August/September.

Affected Areas
Statewide

Details
BBD was detected in New Jersey in 1935, and has impacted American beech trees and forests in the northern half of the state. Although low populations of beech scale have been found in the southern part of the state, the Neonectria fungi have not yet been detected in South Jersey.

Beech bark disease (BBD) is a disease-insect complex between the fungi (Neonectria faginata and N. ditissima) and the beech scale insect (Cryptococcus fagisuga), native to Europe. When the beech scale feeds on the beech trees, it creates a tiny wound that allows the Neonectria fungi to enter and infest the tree. BBD was accidentally introduced to Nova Scotia in the 1890s on an ornamental beech imported from Europe, and by the 1960’s, BBD was well established in the New England states.

The Neonectria fungi develop small, red perithecia, or fruiting structures, that often grow in a circular pattern. The fungi also cause the infected areas to callous, causing a raised or sunken circular callouses that are visible on the trunks of infected trees. The beech scale insect is almost microscopic in size, but it forms a woolly, white coating on the outside of its body, which makes them more visible, especially when there are numerous scale insects infesting a tree. The beech scale insects tend to congregate in bark cracks or areas where the bark is rough, but they can also establish on smooth parts of the bark as well.

Although there are no effective treatments for BBD, researchers have found American beech trees that exhibit resistance to BBD. These trees are tested for resistance then grown in orchards to serve as future sources of seeds for American beech restoration efforts.

Susceptible Species
American Beech Signs of Infestation Sparse foliage, woolly beech scale insects, small red fungal fruiting bodies, round sunken or raised callouses

Affected Areas
Northern New Jersey

More information

Details
Oak wilt is a fungus that causes rapid mortality in oak trees around July - September. Oak trees in the red oak family are more susceptible than those in the white oak family, but both can be infected with the fungus. Red oak trees can die within weeks or months after infection, whereas white oak trees die after a year or more. Oak wilt has not yet been detected in NJ, but has been detected in neighboring states including New York and Pennsylvania.

The oak wilt fungus is spread in two ways, 1) by sap-feeding insects or 2) by underground root grafts. The fungus is able to stick to the bodies of insects that feed on infected trees and then feed on healthy trees. In areas with known oak wilt infection, pruning of oak trees is discouraged during the summer and early fall months when sap-feeding insects are active and can transmit oak wilt when feeding on the wound created at the pruning site. The fungus is also able to move from tree to tree via underground root grafts. For this reason, trees infected with oak wilt often follow a concentric pattern of spread.

Oak wilt is very difficult to identify based on trees symptoms alone, because there are other insects, pathogens, and factors that can cause oak leaf discoloration and rapid tree death. The most effective method to confirm oak wilt is through laboratory testing.

Although there is no treatment for oak wilt, it has successfully been eradicated from areas when identified and addressed early. Eradication efforts include the removal and proper disposal of known infected trees in addition to a buffer of asymptomatic trees. In addition, the root systems of the buffer trees removed must be severed or killed to prevent further spread to adjacent oak trees.

In NJ, a common look-a-like is bacterial leaf scorch (BLS). See BLS for more information.

Susceptible Species
Oak Wilt affects both Red and White oak species

Signs of Infestation
Leaf discoloration in July - September, rapid tree mortality, Fungal mats, bark cracking

Affected Areas
Not yet found in NJ

More information

Details
Larvae feed on the bottom of oak leaves, leaving only a leaf skeleton of veins behind. Repeated defoliations may affect vigor or kill the tree.

Susceptible Species
Red and white oaks

Signs of Infestation
Skeletonized or transparent leaves, defoliation starting in upper crown, larvae feeding on leaves

Affected Areas
Northern New Jersey

More information

Details
Thousand cankers disease (TCD) is a disease-insect complex between a fungus (Geosmithia morbida) and the walnut twig beetle (WTB) (Pityophthorus juglandis), believed to be native to the western states. Although WTB and Geosmithia are found in western walnut species, it mainly affects trees that are already under stress or declining. However, in black walnut, an eastern species, TCD successfully infects healthy trees, causing cankers, dieback, and eventual tree death.

Black walnut trees planted in western states are susceptible to TCD, and it was in Oregon and Utah where walnut decline was first observed in the 1990s. However, it was not until 2007 when Geosmithia was identified as the causal agent of the walnut decline. TCD has not yet been detected in NJ, however, the closest known detections are in Pennsylvania and Maryland.

The disease-causing fungus (Geosmithia morbida) is transmitted into the phloem of the tree by the walnut twig beetle (Pityophthorus juglandis) as it constructs its galleries. Cankers develop around the galleries as a result of the fungus and coalesce to girdle the branch or stem. The cankers are usually small in size, no larger than the size of a quarter. It takes thousands of cankers to cause tree mortality, which is where the name comes from.

Susceptible Species
Black walnut

Signs of Infestation
Branch dieback, epicormic sprouts on trunk or base of tree, many small cankers on branches and bole, tiny bark beetles, circular or oblong cankers under bark, tiny entrance and exit holes

Affected Areas
Not yet found in NJ

Details
Jumping worms, first identified in Wisconsin in 2013, are an invasive earthworm introduced to North America from Asia. Jumping worms differ from other earthworms as they live close to the soil surface, devouring the organic soil and leaf litter layers leaving behind massive amounts of coffee ground-like excrement known as castings. Presence of these worms is extremely detrimental to the Northeast as seedling recruitment and regeneration is largely dependent on available litter layer and organic material necessary for seed germination. Limited organic matter and leaf litter layer also negatively impacts small reptiles, ground nesting birds and small mammals.

Jumping worms can be identified from other common earthworms through their brownish gray color and their distinct white clitellum (collar) that encircles them entirely. These worms also have a unique snake-like, thrashing movement that they exhibit upon being disturbed and can sometimes jump or hop into the air during their thrashing.

Jumping worms are parthenogenic, meaning they self-fertilize and do not need mates. They reproduce and deposit egg-filled cocoons in August and September which hatch in April and May. Jumping worms are extremely sensitive to freezing temperature which induces mortality during the first freeze of the year. The European nightcrawler (Lumbricus terrestris) is often mistaken for the jumping worm but can be distinguished easily through their movement as the European nightcrawler has a slow lethargic movement. The European nightcrawler also has a darker color clitellum that is less distinct from their body color than a jumping worms.

Signs of Infestation
Large amount of coffee ground-like excrement known as castings, or presence of adult worms on the surface or upper layers of the soil during the summer and fall.

Affected Areas
Likely statewide, but confirmed detections in Bergen, Essex, Hunterdon, Mercer, Middlesex, Monmouth, Morris, Ocean, Passaic, Sussex, Union, and Warren Counties

Details
Originally from Asia, The Elm Zigzag Sawfly (EZZ) was first discovered in Europe in 2003, Québec in 2020, and Frederick County, Virginia in 2021. EZZ is a foliage feeder with a wide range of host plants but represents a threat to elm trees of the genus Ulmus in the United States. EZZ defoliates elm trees and leaves behind a unique ‘zigzag’ pattern on leaves it feeds upon. EZZ is a newly emerging pest in the United States and its potential range and impacts remain to be further studied.

Help Look For Elm Zigzag Sawfly

Elm Zigzag Sawfly Article

Susceptible Species
Elms (Ulmus sp.)

Signs of Infestation
Zigzag defoliation of Elm leaves

Affected Areas
Currently not detected in New Jersey, first North American detection was in Quebec, Canada in 2020, with recent detection in Virginia in 2021.

Details
Oak Shothole Leafminer is a small species of fly in the family Agromyzidae and is native to most of the east coast from Maine to Georgia. The fly is commonly found throughout NJ, where adult females feed on buds and newly emerged leaves of oaks. The feeding behavior results in a small circular incision which increases in size as oak leaves continue to grow in Spring and early Summer. Although damage from Oak Shothole Leafminer can be widespread and significant, the flies are kept in check by native control agents preventing widespread tree mortality and the need for insecticide use.

Susceptible Species
Oaks (Quercus sp.)

Signs of Infestation
Circular, shothole damage among oak leaves sometimes described as having a “Swiss cheese” appearance.

Affected Areas
Likely statewide, but reported detections in Bergen, Burlington, Hunterdon, Middlesex, Monmouth, Morris, Ocean, and Sussex

Details
Verticillium Wilt is caused by two species of soil borne fungi, Verticillium dahlia and Verticillium albo-atrum. The fungus enters a tree through the root system where the fungus restricts the flow of water to certain parts of the tree resulting in the yellowing of leaves and wilting of branches.

Susceptible Species
Eastern Redbud (Cercis canadensis) and Maples (Acer sp.) and are among the most affected tree species

Signs of Infestation
Often, infected branches will show bright green or dark brown bands, streaks or flecks if cut.

Affected Areas
Statewide

Details
Fall Webworm is a species of moth native to the United States. Adult females will lay eggs under the leaves of deciduous trees and shrubs between July and August. When eggs hatch, larvae will spin a small web over foliage to feed on. The web size will increase and expand it as larvae continue to feed. The moths are a minor insect pest and do not kill host trees. Populations of Fall Webworm are kept in check by native parasites and predators.

Susceptible Species
Most deciduous tree species, but tend to prefer walnut, cherry, and crabapple trees

Signs of Infestation
Tents on tree branches present in late summer and fall, Browning foliage incased in webs with feeding larvae

Affected Areas
Statewide

Details
The Chestnut Blight fungus, Cryphonectria parasitica, is native to Asia and was first introduced to North America in the early 1900s. The fungus originally infects its native host trees, the Chinese chestnut (Castanea mollissima) and the Japanese chestnut (Castanea crenata). When introduced into the United States, the fungus spread rapidly across the wide range of American chestnut, Castanea dentata. Mortality of most adult American chestnut trees had been observed by the 1940s. The Chestnut blight enters through wounds of trees and attacks the inner bark and cambium of susceptible trees that ultimately girdle the tree, causing chronic dieback or mortality of the tree. American chestnut trees can still be found in forests of New Jersey but are often of small diameter with many stump sprouts from continual dieback caused by the fungus. Starting in the 1930s and continuing today, efforts are underway to repopulate the United States with new varieties and hybrids of American chestnut trees that are resistant to the blight.

Susceptible Species
American chestnut (Castanea dentata) and American chinquapin (Castanea pumila)

Signs of Infestation
Small orange or brown areas on the bark of an infected tree

Affected Areas
Statewide

Details
Dutch elm disease (DED) is caused by a fungus spread by several species of elm bark beetles with the most common including Hylurgopinus rufipes, Scolytus multistriatus, Scolytus schevyrewi. The fungus is endemic to Asia but was accidentally introduced to Europe and was identified in the Netherlands in the 1920s by Dutch scientists. DED was first introduced to the United States in the 1930s and has caused wide-spread mortality of the elm species since introduction. The fungus infects the tree through elm bark beetles and larvae. In an attempt to stop the virus from spreading, elm trees will plug areas of their vascular system that causes decline which is noticeable in a trees canopy and ultimately, mortality of the tree.

Susceptible Species
Elm species (Notably Ulmus americana and Ulmus rubra)

Signs of Infestation
Wilting and/or yellowing of leaves that begins at the top of the tree and moves downward toward the trees base

Affected Areas
Statewide

For an annual update on the projects the New Jersey Forest Health Program is working on, visit the USDA Forest Service's website and click on New Jersey.