DISC's Invasive of the Day series in honor of National Invasive Species Awareness Week 2015!
During the week of February 22-28, 2015, we will be profiling a different invasive species every day!
For more information regarding National Invasive Species Awareness Week, including nationwide volunteer events, educational programs, and more, please visit NISAW's webiste!
Friday, February 27, 2015
Emerald Ash Borer
Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is an exotic beetle that was discovered in southeastern Michigan near Detroit in the summer of 2002. The adult beetles nibble on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients. Emerald ash borer probably arrived in the United States on solid wood packing material carried in cargo ships or airplanes originating in its native Asia.
Since EAB was discovered 13 years ago in southeastern Michigan, it has quickly spread throughout many northeast and mid-west states. Several spot infestations are very close to Delaware in Maryland, Pennsylvania, and New Jersey, but it hasn’t been found within our borders yet. Ash is a common forest tree in many areas with mature infestations – ie. the Great Lakes states – and stands there are easily recognized. Because the trees are all dead.
Once established, Emerald ash borer (EAB) will spread quickly and infest all ash trees in a city or community. With no control measures taken, the city can expect all ash trees to die within 6-10 years. For a city or community that is responsible for maintaining street, park or other trees, this presents a huge financial liability. For example, Fort Wayne, IN first discovered EAB in 2006 and had to remove 9,000 trees between 2011 and 2012. Fort Wayne reported not only financial hardship, but the massive tree removal exceeded what local arborists could handle. In addition to the costs, EAB threatens city tree canopy cover which affects the value of property and parks.
Given this reality, cities and communities must plan their response to EAB to limit sudden financial costs by spreading control costs over several years. Two methods are used which work together. Begin removing ash trees early to reduce inventory and apply chemical treatments to some trees to prevent infestation.
Tree replacement and canopy cover is important for many communities. Trees selected for replanting should be diverse to avoid future pest problems that may impact other species. Beginning to replant trees today can help reduce the canopy loss that EAB will cause.
If you have questions, have a declining ash tree, or believe you’ve seen EAB – contact Jimmy Kroon at the Delaware Department of Agriculture. 302-698-4586 or firstname.lastname@example.org
Most recent Emerald Ash Borer map
Evaluate management options with the Purdue University Cost Calculator
Learn more at EAB University
Insecticide options for protecting trees
Thursday, February 26, 2015
Oplismenus hirtellus spp. undulatifolius
(Fairfax County Park Authority)
Wavyleaf basketgrass is an aggressive, introduced subspecies of the native basketgrass Oplismenus hirtellus. Native to parts of Europe and Asia, it is thought to have arrived in the United States through discarded and contaminated hanging flower baskets. It was first discovered in Patapsco Valley State Park, Maryland in 1996. Currently, its distribution is limited to a handful of sites in Maryland and Virginia, including 80 acres in Shenandoah National Park.
The leaves of Wavyleaf basketgrass are flat, dark green and have rippling waves across the blades. They are similar in appearance to invasive Japanese stiltgrass (Microstegium vimineum) leaves, but come to a sharper, more elongated tip and lack the silver mid-stripe of stiltgrass leaves. The leaf sheath and stem are hairy. In the autumn, Wavyleaf basketgrass forms sticky awns (seeds), which easily attach to clothing, animals and vehicles.
Wavyleaf basketgrass is a perennial, extremely shade tolerant, and can easily out-compete the native vegetation of deciduous forests to form a monoculture. This, combined with its ability to quickly spread by rhizomes and sticky seeds, could allow it to invade nearby areas. It is of little value to native wildlife. Although it is not currently present in Delaware, its seeds could make their way here on the clothing or vehicles of unsuspecting visitors. Early detection and rapid response will be essential in preventing this invasive from getting a foothold in our forests. Currently, groups in Maryland and Virginia are working to eliminate Wavyleaf basketgrass from known sites. Until these efforts are completely successful, the threat to Delaware remains real.
If you find an infestation of Wavyleaf basketgrass in Delaware, please carefully compare it to several lookalikes: invasive Japanese stiltgrass (Microstegium vimineum); non-native Small Carpetgrass (Arthraxon hispidus); and native Deertongue grass (Dicanthelium clandestinum). Suspected Wavyleaf basketgrass colonies should be reported to State of Delaware botanist (DNREC) Bill McAvoy: email@example.com
Wednesday, February 25, 2015
Thousand Cankers Disease
Thousand Cankers Disease was first identified in Colorado black walnuts. It is a fungus, Geosmithia morbida, which is spread by the walnut twig beetle, Pityophthorus juglandis. Thousand Cankers Disease, true to its name, causes numerous dark cankers surrounding the walnut twig beetle galleries and eventually kills the tree. The disease and walnut twig beetle are both native to the western USA, though little evidence of walnut mortality was found prior to 2003. It has since been found in most Rocky Mountain and west coast states from New Mexico to Washington.
In 2010, Thousand Cankers Disease was found in Knoxville, TN. This was the first report in the Eastern USA. It has since been found in isolated areas of Pennsylvania, Virginia, North Carolina, Ohio, and Indiana. In 2014, Thousand Cankers Disease was detected in Maryland a few miles west of the Delaware state line near Newark.
The Delaware Department of Agriculture set traps for Walnut twig beetle in 2014. Traps were located statewide and many were near Newark. We have also done visual surveys for Thousand cankers disease for several years. So far, neither Walnut twig beetle nor Thousand cankers disease have been found in Delaware.
(Walnut Twig Beetle)
There is no Federal quarantine for Thousand cankers disease. Several states, including Maryland and Pennsylvania, have enacted their own quarantines to restrict the movement of walnut out of infested areas.
Learn more about Thousand Cankers Disease at http://www.thousandcankers.com. Contact Jimmy Kroon, Environmental Scientist II at the Delaware Department of Agriculture with questions, concerns or possible reports of Thousand Cankers Disease in Delaware. 302-698-4586 or firstname.lastname@example.org
Tuesday, February 24, 2015
Northern Snakehead, a native fish of China and Russia, were brought to the U.S. for the live food fish market. Unfortunately these exotic invaders escaped or were illegally stocked and now occur in at least eleven states where they potentially threaten native fish and wildlife resources. The Northern Snakehead has since been designated as ‘injurious wildlife’ which makes importation and interstate transport illegal under the Federal Lacey Act. These voracious predators feed on a variety of invertebrates, fish, amphibians, reptiles, birds and even small mammals! They can be identified by their long cylindrical shape, long dorsal and anal fins, and dark, irregular patches on their sides; but are probably best known for their large mouth with many sharp teeth. Because of the ability to breathe atmospheric oxygen they can survive in stagnant shallow waters which gives them an advantage over many native species. Despite inspiring the movies ‘Frankenfish’ and “Snakehead Terror” they are incapable of walking over land, but are very protective of their young and will bite if threatened while protecting their nest.
In Delaware, Northern Snakehead are known to occur in two river systems (Christina River and the Nanticoke River), four private ponds, and in Becks Pond which is one of the most popular public fishing ponds in Delaware. Unauthorized stocking of this fish in Becks as well as several other ponds has contributed to its spread within the Christina River watershed. A regulation passed in 2013 prohibits the transport, purchase, sale and possession of live snakeheads in Delaware, so hopefully this will curtail illegal stocking. Unfortunately once established this hardy fish has proven difficult to eradicate, making preventative measures even more crucial. The Division of Fish and Wildlife is closely documenting the occurrence of this species and collecting biological (length, weight, sex, stomach contents), genetic (small clip of fin tissue or blood sample), and age data (scales and otoliths or ‘ear stones’) in an effort to gain a better understanding of the potential impact this species could have on Delaware’s freshwater ecosystems. Anglers have been very helpful with this effort by killing and providing their catches of Northern Snakehead to the Division. Anyone catching a Northern Snakehead in Delaware waters is encouraged to kill it and notify the Division of Fish & Wildlife at (302) 735-8654 or 739-9914.
Monday, February 23, 2015
Rose family (Rosaceae)
A native of Asia, Pyrus calleryana was first introduced to the U.S. in 1916 as rootstock for cultivated pears. Around 1950, interest from the horticultural trade began to grow and a non-spiny seedling was selected and named “Bradford” pear. The Bradford pear, also referred to as Callery pear, is a medium-sized deciduous tree well suited for urban planting. Its abundant spring flowers – borne on an attractive tear-dropped shape – combined with its ability to tolerate a wide range of soil conditions made the Bradford pear the second most popular tree in America by the 1980’s. At the time, the Bradford pear was thought to have no impact on the natural environment because it was a hybrid that could only produce sterile fruit. Its popularity led to the development of several other cultivars that included the Aristocrat, Cleveland, Chanticleer, and Respire.
By the late 1990’s it had become apparent that these new cultivars were able to cross-pollinate as pear trees began popping-up along roads, rights-of-way and old fields. With birds and other wildlife readily dispersing the now viable fruit, the Bradford pear gained new attention as an aggressive invader.
These “wild” pear trees are highly competitive, which allows them to invade natural areas. Once established, they form dense thickets that produce root sprouts that push out native plants intolerant of the deep shade. Once established, these new stands can subsequently interbreed, producing more viable seed and furthering expansion and dispersal of the wild stand of the species. A study conducted in 2005 on the spread and distribution of Bradford pear reported the species to have established stands outside of cultivation in over 152 counties in 25 states in the United States. The following consequences can occur as a result of this interbreeding:
In the landscape setting, the Bradford pear and its many cultivar cousins exhibit several problems. The growth habit of the tree’s crown is problematic because it lacks a central leader, resulting in many weak structural supports. Combined with its brittle wood, the main branches have a tendency to split during wind and ice storms, leaving ugly wounds or decimating the tree altogether. The Bradford pear is a short-lived tree with an average life span of only 20 years and requires aggressive pruning to combat its poor branch development. For these reasons and the impact on natural areas, Bradford pears have been placed on Delaware’s “Do Not Plant List.”
If you have pear trees planted in your landscaping it is recommended that they be removed as they begin to deteriorate or become unhealthy and replaced with native trees or shrubs. Several native species such as Allegheny serviceberry and white fringe tree offer springtime blooms.