One of the most popular flowering trees in Maryland is the Crapemyrtle (Lagerstroemia indica). Producing an abundance of showy flowers in late summer and early fall, it brings a splash of color when most trees and shrubs are going dormant. It also has a pleasing, smooth bark, which reveals multiple colors as it peels. It is one of the nursery industries biggest sellers and because of its general lack of diseases and insect pests in our area is an easy plant to maintain in the landscape. That has changed dramatically with the detection of Crapemyrtle bark scale (Acanthococcus lagerstroemiae), a scale insect that covers the bark of crapemyrtles, and feeds on the sap of the tree. This pest has also been detected on other plants, including beauty berry, a Maryland native, and soybeans. Because of the potential spread to native plants and serious damage to a popular landscape plant, the Crapemyrtle bark scale has been selected as this month’s Maryland Invasives Species Council Invader of the Month.

Crapemyrtle bark scale was first detected in the United States in central Texas in 2004. It has since spread East and north to Virginia and Delaware. It has now been documented in Maryland. 

Crapemyrtle bark scale is a bark or felt scale, slightly different than a soft scale insect, but like soft scales produce a waxy coating to protect the larvae, adults and their eggs. These are small insects, no more than 2 millimeters in length. Females do not move once they attach to the twig or branch. Males are winged and fly to the females to mate. Once the females produce an ovisac, or egg case, they die, leaving the eggs protected under the waxy coating. When they hatch, the nymphs or ‘crawlers’ will move to a fresh site on the twig and start the cycle over again. As with most scale insects, they are most vulnerable in the crawler stage. They can attach anywhere there is room on the twig or branch and will concentrate around pruning cuts. There are 2 to 4 generations in a year, reproducing rapidly. The number of generations in Maryland and Delaware have not been documented, however, researchers Dr.’s Stanton Gill of University of Maryland Extension, and Brian Kunkel, of University of Delaware have a study in progress to determine this. Crapemyrtle bark scale also produces copious amounts of “honey dew,” a secretion which attracts insects feeding on the sugars in the extract, and also provides a medium for sooty mold, that stains the foliage and bark, leaving an unsightly appearance. Crapemyrtle bark scale can be fatal in extreme situations. In most instances however, the effect is a combination of a degraded visual appearance, and the weakening of the tree.

Crapemyrtle bark scale is not just found on its namesake. It has been found on American beautyberry, a popular shrub often used in landscape and restoration plantings. Potentially, there are up to 30 different plants that could be a host for this insect, including persimmon and soybeans. The impacts on crapemyrtle alone is enough to cause concern as it is one of the most popular choices as a flowering small tree in landscapes in Maryland. Crapemyrtle is popular not only for its flowering ability but also for its general lack of insect pests, with crapemyrtle aphids being the other pest that causes problems. This insect pest will increase the need for maintenance, including pesticide use.

Crapemyrtle itself is a nonnative invasive species with documentation in most of the southeastern states including Maryland. Fortunately, it is not as aggressive as other invasive tree species. The best way to avoid Crapemyrtle bark scale is not to plant crapemyrtles. There are native alternatives such as service berry Amelanchier arborea, flowering dogwood Cornus florida, redbud Cercis canadensis, and witch hazel, Hamamelis virginiana L. that have showy flowers as well. If you already have crapemyrtles, check for infestations and if severe, contact a certified arborist. Control in light infestations may just require spraying a with a garden hose to wash them off the branches and twigs. This can also alleviate the sooty mold that grows on the honeydew that they produce in abundant amounts.

 Severe cases may require the use of pesticides. Horticultural oil and insecticidal soaps are often used on scale insects. Insecticides such as the neonicotinoids can also be used on soft scales but must be applied by professionals. Because of the risk of harming pollinators when using neonicotinoids, growth regulating pesticides such as pyriproxyfen (trade name -Distance) and Buprofezin (trade name – Talus), which interfere with the development of the larvae and \or eggs to maturity, are recommended from an Integrated Pest Management position. Pesticides must be used according to the label, and while wearing personal protection equipment to protect the applicator. If help is needed, contact your agricultural extension agent or a licensed commercial applicator.

It is believed that this invasive pest will spread rapidly throughout Maryland in the coming years.  Careful monitoring and measures taken to control it will lessen the impact it will have on one of the most popular ornamental trees in Maryland.

https://extension.umd.edu/resource/crapemyrtle-bark-scale-new-problem-home-landscapes

The post Watch out for Creepers on your Crapemyrtle! first appeared on Maryland Invasive Species Council.

Attention anglers!  What lies in your bait bucket has the potential to damage Maryland’s waters and the quality of your most prized fishing hole.  Your favorite type of bait may help you catch a big fish, but it may also be an invasive species.  Rusty crayfish, fathead minnow, goldfish, red swamp crawfish, banded darter, virile crayfish, red wigglers, rainbow darter, and nitro-worms, to name just a few of the non-native bait species that have been used in Maryland waters, are now established in the state.  Some of these introductions have caused little harm, while others have caused considerable ecological damage.  Many other bait species and bait-related diseases are threatening to join the list of Maryland invaders.  With the 2021 fishing season underway, your actions can make the difference and help prevent further introductions of invasive bait species.  For this reason, the Maryland Invasive Species Council has chosen live bait as the July 2021 Invader of the Month.

Dumping unused bait into a stream, river, lake, or on shore is often viewed by anglers as humane or even beneficial to game fishes.  However, this simple act can have unexpected repercussions.  The release of live bait by anglers has been responsible for the introduction of invasive crayfishes, fishes, earthworms, and fish diseases across the nation.   Following their introduction, invasive bait species can quickly overpopulate invaded areas and reduce native biodiversity, water and habitat quality, and cause dramatic changes in ecosystem function.   These changes can cascade through an aquatic food web, affecting everything from algae to commercially and recreationally important fishes.  Even a benign-looking earthworm can have ecological impacts.  Dramatic changes to forests of northern North America have been linked to invasive earthworms such as Lumbricus terrestris, a European species commonly sold as bait.  These invasive earthworms alter soil chemistry, reduce the diversity of other invertebrates, amphibians, and native vegetation, and hasten the spread of invasive plants.  At least nine non-native earthworms have been introduced in Maryland – many of these are common bait species.  Some of these have impacted Maryland ecosystems (see Invader of the Month https://mdinvasives.org/iotm/april-2015/).

The earthworms, crayfishes, and fishes used as bait are not the only concern.  Even the packing material within a bait container can harbor small invaders.  For example, live bloodworms are a popular bait among anglers targeting spot, croaker, striped bass and other fishes in the Chesapeake Bay and its tributaries.  Bloodworms used by anglers in the bay and Mid-Atlantic region originate from coastal Maine where they are harvested from intertidal mudflats, packed in seaweed known as wormweed, and shipped to bait dealers worldwide.  A recent study of the bloodworm trade conducted by scientists at the Smithsonian Environmental Research Center found that a wide variety of small snails, crabs, isopods, amphipods, and other invertebrates live among the wormweed and can survive the transit from Maine to Maryland hidden within a bloodworm bait container.   Anglers who chose to dump their unused worms as well as the wormweed from their bait containers into Chesapeake Bay waters may unknowingly introduce another problematic, invasive species. 

Photo Credit:  Dr. Amy Fowler – George Mason University

Bloodworms, a common bait used in the Chesapeake Bay, are often imported in containers of wormweed (pictured here) from the coast of Maine. This wormweed can contain a wide variety of other non-native, potentially invasive ‘hitchhikers’ that could pose a risk if discarded in Maryland waters.

Parasites, fungi, fish pathogens, and other microscopic organisms associated with live bait can dramatically reduce the health of anglers’ favorite game fishes.  For example, Viral Hemorrhagic Septicemia (VHS) is a highly contagious disease that has caused massive fish kills in the Great Lakes since 2005 and has spread to other waters in New York, Ohio, Wisconsin, and Michigan.  This disease  infects over 40 species of fishes including rainbow trout, brown trout, walleye, yellow perch, channel catfish, northern pike, and black crappie.    The use and release of contaminated bait is believed to be one of the important vectors responsible for the spread of this disease.  To prevent its spread, natural resource agencies and bait dealers in the Great Lakes region have taken steps to prevent the culture, sale, and export of contaminated bait. 

Fortunately for Maryland, these actions should greatly reduce the likelihood that VHS hitchhikes make it into the state on contaminated bait.  However, complete protection of our waters from invasive bait species and from fish diseases like VHS requires an informed and vigilant angling community here in Maryland. Your actions can make all the difference. 

You can help prevent the spread of invasive bait species by doing the following:

• Never release unused live bait and packing material directly into water or on shore
• Give your unused live bait away to other anglers
• Save your bait for your next fishing trip
• Dispose of your unused live bait humanely by placing it in a freezer
• Never carry organisms from one watershed to another

And most importantly, spread this message to your fellow anglers.  Give them this information and tell them to pass it on!

For more information on invasive bait species and Maryland’s bait regulations, visit http://www.dnr.state.md.us/invasives/

Originally posted as the Invader of the Month in April 2011.  Updated May 2021.

The post Take the Bait…don’t dump it! first appeared on Maryland Invasive Species Council.

We may be under a stay-at-home order, but the natural world is on the move as spring comes into full swing. Unfortunately, that includes invasive species. One invasive threat, that has been on the move in Chesapeake watershed since the 1960s, is invasive catfish. Sightings and catch of these fish pick up each spring as more anglers start hitting the water. As fishing season kicks into gear, we picked blue and flathead catfish as the April Invaders of the Month.

Both flathead and particularly blue catfish are considered good recreational fish. They offer some challenge when catching and good eating. That’s why these invasive catfish were introduced to the James and Rappohanok rivers in the 1960s. Both species are native to the central US in the Mississippi, Ohio and Missouri river systems. From the initial introduction in the James and Rappohanok, the blue catfish has spread to the Potomac and eventually to every major tributary of the Chesapeake Bay. Flathead has spread less, but can still be found in the Potomack, Elk, and Sassafrass rivers. 

Predation is the main threat of invasive catfish to our native species and ecosystems. While most of the catfish diet consists of vegetation, it does prey on important and imperilled animals in the bay. Menhaden, American shad and other fish make up small portions of the blue catfish’s diet. In areas with higher salinity, blue crabs can make up a significant portion of their diet. Despite the fact that predation is not heavy on many natives, any amount can be detrimental to commercial fisheries, recreation, and restoration efforts.

Both invasive species can be distinguished from our native species with relative ease. The blue catfish has smooth blue-slate skin and can grow quite large. The record size catch of blue in Maryland is 84 pounds, versus the record 9.6 pound native white catfish. Flathead catfish, though not as large as blue catfish, is also significantly larger than native catfish. Flatheads generally look more similar to yellow and brown bullheads than white catfish. However, flatheads have a projected lower jaw unlike the bullheads.

When we are able to head out again, all of us anglers can do our part to help control these invasive catfish. Catch them! The Maryland Department of Natural Resources asks anglers to remove and kill any blue and flathead catfish they catch. Catch and release of these fish is discouraged, as they are invasive predators and pose a serious long-term threat to our native species. It is also illegal to transport live blue and flathead catfish into another body of water. If you don’t fish, you can always eat them!

For more information, visit:

https://dnr.maryland.gov/fisheries/Pages/catfish.aspx

https://dnr.maryland.gov/fisheries/Documents/Invasive_Catfish_%20Fact_Sheet.pdf

The post Colossal Catfish Cause Conservation Complications first appeared on Maryland Invasive Species Council.

As temperatures begin to rise and we start looking for signs of spring, don’t be fooled by these little yellow beauties as you stroll through the woods looking for wildflowers. Lesser celandine (Ficaria verna), is a member of the buttercup family and more commonly known as fig buttercup. It is a non-native invasive that will quickly out-compete our native spring ephemerals and many more native plants in our natural areas. Introduced into the United States in the late 1800’s from Europe and parts of northern Africa and Asia as an ornamental, this plant creates thick mats across the forest floor, crowding out other vegetation above ground, and growing tubers below ground that compete with plants for root space. The plants are highly visible in early spring, which is why they have been selected as Maryland Invasive Species Council’s March Invader of the Month.

The attractive bright yellow flowers have eight to 12 petals and are about 3 inches across, blooming from late winter to early spring. After flowering, the shiny, dark green kidney-shaped leaves carpet the forest floor until the mid-summer. The thick tuberous roots, about a half an inch each in size, form a dense network below the soil surface. By June, the foliage has died back, and the plant becomes dormant, though the tubers continue to occupy root space below ground year-round. Lesser celandine primarily reproduces through these underground tubers, so disturbance, including pulling, flooding and digging by animals can result in further spread of the plant.

Because lesser celandine emerges so early, it can out-compete many native ephemerals, taking advantage of early-season sunlight before trees begin to leaf out. The resulting dense mat formed will shade our native spring wildflowers, preventing them from emerging, and likewise disrupting native pollinators searching for early-season nectar sources. 

Lesser celandine can be controlled chemically or manually. For chemical removal, a 1-2% glyphosate solution can be applied during the active growing and blooming period, between February-March when temperatures are above 40^oF. Spraying during this time will minimize killing other native plants in the vicinity as most should not have emerged yet, but precautions should still be taken to minimize spraying non-target plants. Manual or mechanical removal of small infestations can be successful but removing all the below ground parts is critical. This plant will readily reproduce vegetatively, so any missed roots or tubers can produce new plants. 

To help ensure long-term success, after removing lesser celandine, replant the area with natives, which will to help control soil disturbance and replenish an important nectar source for insects. Lesser celandine is often confused with a desirable native wetland plant called marsh marigold (Caltha palustris). While they have similar leaf shapes and color, marsh marigold flowers only have five to nine petals and the plant does not produce tubers. Other native alternatives to consider include wild ginger (Asarum canadense), bloodroot (Sanguinaria canadensis), twinleaf (Jeffersonia diphylla), cutleaf toothwort (Cardamine concatenate), Dutchman’s breeches (Dicentra cucullaria), Virginia bluebells (Mertensia virginica) and golden ragwort (Packera aurea). 

Maryland banned the sale of lesser celandine beginning in 2017.  However, it may still be commercially available in other states, and all varieties should be considered invasive.

For more information, please visit:

Brandywine Conservancy

Ecosystem Gardening

Plant Invaders of Mid-Atlantic Natural Areas

The post Deceptive little buttercup is foe, not friend first appeared on Maryland Invasive Species Council.

With smooth grey bark and bronze leaves lasting deep into winter, the American beech (Fagus grandifolia), is a popular and easily recognizable tree in the eastern forest. It is an ecologically important tree, as it is one of the lone hard mast producers and a climax species of the northern hardwood forest. For over a century, this species has been under threat from beech bark disease. Partially caused by the invasive beech scale insect, the disease was discovered in Nova Scotia in 1890 and has since spread to most of New England and beyond. Beech bark disease has had a devastating impact on beech trees, but there is a newer threat to this species that has researchers on the lookout – beech leaf disease (BLD). As beech trees are so visible this time of year, beech leaf disease has been selected at MISC’s February IOTM.

In 2012, a number of trees in Lake County, Ohio were found with distinct symptoms on their leaves, marking the discovery of beech leaf disease. The symptoms of beech leaf disease were not seen on any other beech trees in the U.S. or the rest of the world. This led biologist John Pogacnik, the discoverer of BLD, to believe that it may be caused by local weather stresses or other abiotic factors. However, after observing the exponential rate of spread, it was determined to have a biotic cause. 

By 2014, the disease had spread to three new counties in Ohio. In 2018, signs of beech leaf disease could be found in 24 counties in Ohio, Pennsylvania, New York and Ontario. While the spread has been rapid, the effects have not been entirely consistent; areas like Lake County have seen nearly all trees infected but to varying rates of decline. Hopefully, this bodes well for disease resistance and, if necessary, breeding a resilient population.

The disease can initially be identified by the darkening bands between the leaf veins, which appear in spring and can still be seen on bronze winter leaves. Later symptoms include the total darkening (while still not crossing the veins), shrinking and ruckling of the leaves. The leaves in the second stage of symptoms are thicker and leathery in the darkened areas.  Symptoms generally start at the lower portion of the tree, working up to the crown. After the leaves are affected, buds can be terminated, leading to dieback, decline and possibly death. Mortality is more likely to be seen on saplings and young trees, though limited mortality has been observed on larger trees. 

The cause of the disease, whether a complex or single agent, is not yet determined. At Ohio State, research is underway, comparing DNA found in infected trees to uninfected ones. Any differing results could point to the cause. The Ohio Department of Agriculture has also found Litylenchus nematodes on infected leaves, though more research must be conducted to determine if they are the sole cause of beech leaf disease. Litylenchus crenatae nematodes are found on beech trees (Fagus crenatae) in Japan. The species was described in 2018, and the American population has since been described as a subspecies.

In Maryland we are a good distance from infected areas, and there is still hope that we won’t see the disease spread to us. However, it’s good to keep a watchful eye and stick with best management practices, like not moving firewood. If you think you see signs of beech leaf disease in your area, contact: Forest Pest Management at 410-841-5922. 

Photo Sources:

Jim Chatfield, OSU Extension, https://bygl.osu.edu/node/1176

Sources

Ewing CJ, Hausman CE, Pogacnik J, Slot J, Bonello P. Beech leaf disease: An emerging forest epidemic.  For Path. 2019;49:e12488. https://doi.org/10.1111/efp.12488 

Popkin, G. (2018). An arboreal murder mystery: What is killing beech trees? The Washington Post. Retrieved from, https://www.washingtonpost.com/national/health-science/an-arboreal-murder-mystery-what-is-killing-beech-trees/2018/07/27/95d18ebc-8c59-11e8-a345-a1bf7847b375_story.html 

Wike, C. (2019) A Mysterious Disease is Killing Beech Trees The Scientist Retrieved from, https://www.the-scientist.com/news-opinion/a-mysterious-disease-is-killing-beech-trees-65358

More information:Beech Leaf Disease – Ontario’s Perspective: Dr. Sharon Reed https://www.youtube.com/watch?v=tDBbik7cUrI

The post “New Leaf Disease is a Beech” first appeared on Maryland Invasive Species Council.

Thursday, Jan. 16, 2020 | 9:30 AM to 12 PM

LOCATION:
Maryland Department of Agriculture
50 Harry S. Truman Parkway
Annapolis, MD 21401

• Click Here for Directions to MDA
  
• Follow signs to Visitor Parking. Walk in through main entrance, visitors must check in at the security desk.
  

AGENDA – Scroll Down

MISC meetings are open to the public.

Please let us know if you might be attending. Send an email to Lane.Heimer@maryland.gov to ask that your name be added to the visitors list.

AGENDA – Download Here

The post MISC Meeting – January 16, 2020 first appeared on Maryland Invasive Species Council.

Cancellation Reason: No MDA room available.

CANCELED: Thursday, November 21,2019 | 9:30 AM to 12 PM

LOCATION: Maryland Department of Agriculture
50 Harry S. Truman Parkway
Annapolis, MD 21401

• Click Here for Directions to MDA
  
• Follow signs to Visitor Parking. Walk in through main entrance, visitors must check in at the security desk.
  

AGENDA – Scroll Down

MISC meetings are open to the public.

Please let us know if you might be attending. Send an email to Lane.Heimer@maryland.gov to ask that your name be added to the visitors list.

AGENDA – Download here

The post CANCELED: MISC Meeting – November 21, 2019 first appeared on Maryland Invasive Species Council.

Many of us have grown up thinking that earthworms are a sign of healthy, fertile soil. However, many earthworms found throughout Maryland are not native. Earthworms can be beneficial in their native ecosystems and agricultural settings, but their ability to re-engineer soil can completely restructure ecosystems and the microbial, plant, arthropod and vertebrate communities that live within them.  Much of what we know about invasive earthworms comes from studies of invasive European earthworm species, whose effects on forests are particularly notable in temperate North America. More recently, ‘jumping worms,’ (the common name for several similar-looking species belonging to the family Megascolecidae, also known as crazy worms, snake worms, Alabama jumpers, Jersey wigglers, Georgia jumpers, pheretimoids), have invaded temperate and tropical ecosystems across the globe. Their distribution is patchy throughout North America, and while often associated with urban and suburban landscapes, they are appearing with greater frequency in natural areas and forests. Once introduced to a location, jumping worm populations grow rapidly, and can grow to high densities in 4-5 years. Due to their ecological, economic and recreational impact, and the difficulty in removing them once they have been established, jumping worms have been chosen as MISC’s Invader of the Month for November.

Figure 1. Jumping worms alter soil characteristics, increasing erosion (left) and creating large macro aggregates (right). (Annise Dobson)

Jumping worm invasions are unique in that they consist of multiple co-invading species including Amynthas agrestis, Amynthas tokioensis, and Metaphire hilgendorfi in temperate North America. Jumping worms grow and mature quickly, and some species can reproduce asexually, thereby quickly reaching high densities from an initially small invading population. They grow and mature much more quickly than European or native earthworms. While both lumbricid and jumping worms remove the organic horizon, the texture of jumping worm invaded soils is more stressful for roots, fungi and soil fauna. This is because jumping worms transform surface soils into large macroaggregates, described as ‘gravely,’ with the appearance of ground beef or spent coffee grounds. These changes to soil lead to erosion, nutrient leaching, root desiccation, and plant death (Fig 1).

The cascading effects of jumping worms on other species are far reaching. In areas of heavy infestation, anything that relies on the forest floor for food and habitat, such as soil fauna, native plants, salamanders, birds and other animals decline. Furthermore, jumping worm tissues can accumulate toxic metals, suggesting they could be a major pathway for metal bioaccumulation in higher organisms. In addition to deteriorating natural systems, jumping worm impacts are being felt by gardeners, plant nurseries, golf courses and community parks. The deep layer of loose castings created by jumping worms is particularly problematic for perennial plants (both native and horticultural), as well as parks and lawns used for recreation.

Jumping worms can be identified all year round by the distinctively granular soil, described as looking like ground beef or coffee grounds. Their presence can be confirmed in late summer when populations grow rapidly, reaching peak size and abundance. Key features include:

• Thrashing behavior and high densities
• Smooth, metallic sheen, often darkly pigmented, and 1.5 to 8 inches long
• Clitellum often cream colored and goes all the way around the body, unlike the lumbricid species which have a raised and pink colored clitellum (Fig. 2)

Because we currently lack any viable control strategies, efforts should be put on limiting  

human-mediated dispersal of adults and cocoons. Fortunately, the worms don’t move very quickly on their own! Best practices include:

• Require clean equipment provisions in logging and landscaping contracts (and encourage your neighbors and local government to do the same
• Treat compost and mulch to 55 ^oC for 3 days
• Prevent dumping of yard waste
• Plant bare-root
• Don’t move soil in tools, equipment, shoes
• Don’t dump bait or compost worms
• Don’t use compost and mulch of unknown origin

For more information see

https://dnr.wi.gov/topic/invasives/fact/jumpingworm/index.html

http://blog.uvm.edu/jgorres/amynthas/

The post The visible invisible: impacts of invasive jumping worms first appeared on Maryland Invasive Species Council.

Invasive vines are colorful and decorative plants that are often used for ornamental purposes for their showy flowers and colorful, sometimes uniquely shaped fruit. They have a downside however, as many invade forested habitats where they can severely limit the growth of, or even kill, trees and shrubs. Fall is a great time to control invasive vines. For this reason, invasive vines are the October Invader of the Month.

Vines are fascinating plants that have evolved a unique strategy that allows them to compete with larger woody plants. Vines use other plants for support to reach sunlight and further their growth, foregoing the need for large root systems and sturdy stems to keep them upright. This ability to climb allows them to grow rapidly and maintain a narrow and flexible stem. The stem of a typical vine has larger vessel elements or water conducting tissue that allows it to bring water to the upper reaches of the plants. It most importantly allows the plant to support more leaves than a tree with a similar sized stem. Vines have been observed to comprise 40% of the total leaf surface area of a forest while accounting for only 5% of the above ground biomass.

Vines are for the most part light loving plants. They grow in the open or on the edges of forests where light is more abundant and where they can find trees for support. They usually start by themselves and will grow toward any objects that can climb. Vine climb by several methods. Some use tendrils or rootlets to latch onto the tree or shrub to hold it as it grows. Others use phototropism to climb by winding around the stem it is climbing. This is called circumnutation. Once they reach the top they will often send out growth looking for adjacent tree to expand to.

There are native vines in the eastern forest. Wild grape(s), poison ivy, and Virginia creeper are the most common ones encountered. All are valuable as providers of grapes or berries for wildlife such as birds and many mammals including foxes, raccoons, and opossums. These vines do climb trees and shrubs to reach light, like invasive vine species but differ in one key characteristic. These vines do not use circumnutation as they climb the tree; instead they use tendrils or modified roots to attach to the tree. Non-native vines like Asiatic bittersweet, Japanese honeysuckle and Japanese and Chinese wisteria do twine around the tree and eventually strangle the stem and kill the tree. This is a serious problem with young and regenerating forests as the seedlings and sapling are killed before they can become established as the replacement for the next stand of trees.

Another way vines can be damaging is by smothering a tree. Once reaching the top of the tree, vines continue to grow covering the crown of the tree and blocking light from reaching the leaves. They often grow across gaps in the canopy and latch onto the adjacent tree. The vine also adds considerable weight to the crown and will often cause trees to collapse under the extra weight. No vine is more capable of this than the legendary Kudzu vine, often called the vine that ate the south. Kudzu will continue to grow until it covers any stationary object including buildings and abandoned vehicles. Kudzu transforms the habitat of an area by creating a blanket of leaves and vines that doesn’t allow other plants to grow. Kudzu, once planted to control erosion has been found to not have a controlling effect on erosion as the stems and leaves are perched above the ground and aren’t in contact with the soil.

Invasive vines also have negative effects on wildlife habitat. Asiatic bittersweet berries are only half as nutritious as those from the native American bittersweet. This has implications for migratory birds that also depend on this food when migrating south in the winter. There is also concern that rising CO² levels associated with climate change will stimulate greater growth of these invasive plants.

Getting control of vines can be difficult. Some vines like Kudzu usually require herbicides to kill. Most produce abundant amounts of seed and develop a seed bank from which seedling will sprout for many years. Mechanical control can work if persistent effort is made to repeatedly cut them until the roots are exhausted of food reserves. The most common method is to cut a “window” in the vine, severing it at the base of the tree, and then again several feet up, to prevent re-attachment. English ivy, one of the most notorious invasive vines in the mid-Atlantic, area can be dealt with mechanically by cutting the vines at the base of the tree and allowing the growth on the tree to wither and die. Pulling English ivy from the trunk can damage the tree or cause dead branches to fall so it’s best to leave it on the tree. The vines on the ground can often be easily pulled up. Again, persistence is required. It’s also important to not let the cut stems lie in contact with the ground. They can root themselves and become reestablished. Instead bag them, and either take them to the landfill, or store them for several months until you are certain they are dead before composting. Beware of the seeds too. They can persist for years.

An important thing to remember is to not plant invasive vines. Many are available for sale in local nurseries. Instead look for native alternatives. Be aware of things like Christmas wreaths made of bittersweet vines. They often have berries on them that can germinate if disposed of carelessly. The good news in the fight against invasive vines is that persistence will lead to success. The challenge is there and real, but it is not hopeless with dedication and application of sustained effort.

The post The Sign of the Times are the Vines first appeared on Maryland Invasive Species Council.

ANNAPOLIS, MD (August, 2019) – Thousand cankers disease (TCD) is a complex problem in walnuts, Juglans spp., caused by the fungus Geosmithia morbida and transmitted by walnut twig beetle (WTB), Pityophthorus juglandis. The beetles tunnel under tree bark and introduce the fungus, causing cankers that eventually coalesce and girdle limbs and branches, resulting in tree death. Walnut twig beetle was first identified in 1928 in Arizona, in Arizona walnut, Juglans major. Slowly, the beetle has spread to other areas of the U.S., including several states in the Northeast. Black walnut, Juglans nigra, began to show widespread decline in the 1990’s. The first cases of black walnut mortality with bark cankers were found in Denver, CO in 2001, and the association of the Geosmithia morbida fungus with these cankers was identified around 2008. By then, nearly all black walnuts in the Denver area were affected. TCD has now been confirmed in MD, VA, PA, and several other neighboring states (Figure 1). 

WTB feeds in the cambium and phloem of larger twigs, branches, and main stem of Juglans and Pterocarya spp. to create brood galleries beneath the bark. As WTB create galleries, they inoculate the phloem with Geosmithia morbida. The fungus colonizes and kills the surrounding cambium and phloem tissue. Cankers form around every beetle feeding site, which may coalesce to form larger ones, eventually leading to tree death. Generations of the beetle move to and from black walnut trees carrying the fungus to the next hole or tree as they create galleries. 

Walnut twig beetle attacks all species of walnut and wingnut (Pterocarya). A considerable range of TCD susceptibility exists among various walnut species, with black walnut being particularly susceptible. As cankers grow within the phloem of black walnut, they reduce the tree’s ability to store and move nutrients. As TCD progresses, cankers coalesce to girdle branches. As the tree weakens, more bark beetles are attracted and more cankers are formed, eventually killing the tree. It may take several years of insect attack and fungal infection before symptoms other than minute exit holes of the beetle on the trunk are visible.

Walnut twig beetle is 1.5 to 2 millimeters long, has a relatively narrow body is reddish-brown to brown cuticle (Figure 2). It makes tunnels beneath tree bark. In such case, the outer bark can be peeled away to expose WTB galleries in the phloem, a key feature for diagnosing the TCD complex (Figure 3). Cankers become oval-shaped and inky black, reaching more than 3 cm in length. However, the bark remains firmly attached to the canker face, making necrotic areas very difficult to observe. Numerous cankers are present in a single tree due to multiple points of pathogen introduction. Small pin-sized holes are associated with each canker, usually denoting the entrance/exit hole for the WTB. Cankers often bleed, leaving dark ooze and staining on the outer bark surface. 

Symptoms start with leaf yellowing and crown thinning of infected trees, which may initially be restricted to a single branch. As the disease progresses, foliage wilts, larger branches die, and eventually the tree dies. In susceptible hosts, trees are typically killed within 2–3 years after external symptoms of leaf yellowing are first observed. TCD was first detected in Maryland in October 2014 and a quarantine was ordered by the Maryland Department of Agriculture to minimize the risk of disease spreading from Cecil County. The beetles were collected from traps in Baltimore in August 2017. On May 1, 2019, a new quarantine order was issued to restrict the movement of infected materials in all of Baltimore City and part of Baltimore County (Figure 4). Introduction of TCD to a new area involves transportation of infected logs, trees, or other untreated wood products which may carry the beetle or fungus. Quarantines restricting the movement of these products help to limit long distance dispersal and manage this disease.

For more information:

Maryland Department of Agriculture, May 1 2019. Thousand Cankers Disease Detected in Baltimore City and County. https://news.maryland.gov/mda/press-release/2019/05/01/thousand-cankers-disease-detected-in-baltimore-city-and-county/

C. Nischwitz and M. Murray. 2011. Thousand cankers disease of walnut (Geosmithia morbida). https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1729&context=extension_curall

US Department of Agriculture: https://www.invasivespeciesinfo.gov/profile/thousand-cankers-black-walnut-disease

Maryland Department of Agriculture: https://mda.maryland.gov/plants-pests/Pages/tcd.aspx

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