DC Ash Trees Exposed to Exotic Pest
Effective immediately, the US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) has added the District of Columbia to a federal quarantine due to Emerald Ash Borer (EAB), Agrilus planipennis. This action is in response to the detection of EAB in Allegany, Anne Arundel, and Howard Counties in Maryland.
EAB, an invasive wood boring beetle, is native to China and eastern Asia. Since its first US detection in Michigan, EAB has been responsible for the death and decline of tens of millions of US ash trees. The interstate movement of firewood from quarantine areas is an especially high-risk pathway for spreading EAB. Accordingly, the interstate movement of EAB-host wood and wood products from quarantined areas is prohibited outside accordance with applicable regulations, including firewood of all hardwood species, nursery stock, green lumber, waste, compost, and chips of ash species.
While the District of Columbia has few ash trees on public property, the District Department of Transportation’s Urban Forestry Administration (UFA) has an exotic pest monitoring program in place to identify and respond to infestations in street trees. Since a majority of ash trees within Washington, DC are located on private property and in natural riparian areas, UFA is undertaking an initiative to inform residents how to address this issue for their own trees and to stop the spread of EAB in Washington, DC. If you have questions about identifying ash trees, calculating the cost of various EAB management strategies, and homeowner treatment options for Emerald Ash Borer, please see the attached documents. For information about restrictions on the movement of firewood and the federal order, please visit the US Department of Agriculture’s APHIS website.
If you need more details on the Federal EAB regulatory program, you may contact the EAB National Program Coordinator, Paul Chaloux at (301) 734-0917. For information on regulatory requirements for movement of quarantined articles out of the District of Columbia, please contact the APHIS State Plant Health Director, Matthew Travis at (410) 631-0073. For information specifically related to Washington, DC homeowner tree issues, please contact the University of the District of Columbia’s Cooperative Extension Agent, Sandy Farber Bandier at (202) 274-7166. Additional general EAB information is available below.
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Emerald Ash Borer
Emerald Ash Borer (EAB) is an Asian beetle, first detected in Michigan in 2002. It has since killed tens of millions of ash trees in southeastern Michigan alone, with tens of millions more lost in Illinois, Indiana, Kentucky, Minnesota, Missouri, New York, Ohio, Ontario, Pennsylvania, Quebec, Virginia, West Virginia, and Wisconsin.
In addition to spreading by natural means, EAB can be transported to new areas in infested firewood, timber, and nursery stock. States and provinces have enacted intense quarantines against moving wood, but it has still cost municipalities, property owners, nursery operators and forest products industries tens of millions of dollars. The challenge before us is to reduce the loss of remaining elms and to choose suitable replacement trees for the ones we cannot save.
In North America, EAB is known to infest all species of ash (Fraxinus spp.). Ash can be recognized by the presence of compound leaves which are arranged opposite of one another on the branches.
Eggs are laid between layers of bark and in bark crevices. Larvae hatch in about one week and bore into the tree where they feed on the inner bark and phloem, creating “S”-shaped galleries. Larvae go through four feeding stages, and then excavate a pupal chamber in the fall, where they will overwinter as prepupae. Pupation occurs in late spring, and adults begin to emerge through “D”-shaped exit holes in May and early June. Adults will remain active until the end of summer.
A commonly encountered beetle, the six spotted green tiger beetle, Cicindela sexguttata, is often mistaken for EAB due to its similar appearance. It is a predator of small insects and is frequently found on hiking trails. There are other insects often mistaken for EAB as well.
Symptoms and Signs:
New infestations are difficult to detect, as damage to the tree may not be apparent for up to three years. Symptoms of an infestation can include branch dieback in the upper crown, excessive epicormic branching on the tree trunk, and vertical bark splits. Woodpecker damage is sometimes apparent.
If you think you have found emerald ash borers in the District, please contact the Urban Forestry Administration.
Courtesy of: USDA Forest Service Northeastern Area State and Private Forestry; NA-PR-05-04; (Revised August 2009)
Dutch Elm Disease
Dutch Elm Disease (DED) introduction into the elm population is devastating what was once considered an ideal American elm street tree—it was graceful, long-lived, fast-growing, and tolerant of compacted soils and air pollution.
Because elm is so well-suited to urban environments, it continues to be a valued component of the urban forest despite losses from DED. The challenge before us is to reduce the loss of remaining elms and to choose suitable replacement trees for the ones we cannot save.
Foliage symptoms: Symptoms of DED begin as wilting of leaves and proceed to yellowing and browning. The pattern of symptom progression within the crown varies depending on where the fungus is introduced to the tree. If the fungus enters the tree through roots grafted to infected trees, the symptoms may begin in the lower crown on the side nearest the graft and the entire crown may be affected very rapidly. If infection begins in the upper crown, symptoms often first appear at the end of an individual branch (called "flagging") and progress downward in the crown.
Multiple branches may be individually infected, resulting in symptom development at several locations in the crown. Symptoms begin in late spring or any time later during the growing season. However, if the tree was infected the previous year (and not detected), symptoms may first be observed in early spring. Symptoms may progress throughout the whole tree in a single season, or may take two or more years.
Vascular symptoms: Branches and stems of elms infected by the DED fungus typically develop dark streaks of discoloration. To detect discoloration, cut through and peel off the bark of a dying branch to expose the outer rings of wood. In newly infected branches, brown streaks characteristically appear in the sapwood of the current year (figure 3). It is important to cut deeply into the wood or look at the branch in cross section for two reasons: (1) As the season progresses, the staining may be overlaid by unstained wood, and (2) if infection occurred in the previous year, the current sapwood may not be discolored.
Courtesy of USDA Forest Service Northeastern Area
Bacterial Leaf Scorch
Bacterial Leaf Scorch (BLS) is a disease of major environmental, economic, and aesthetic importance. Urban trees such as sycamore, red maple, dogwood, American elm, several species of oak, and agricultural crops can become infected and eventually die.
This disease has been observed in District of Columbia street trees. It is caused by a vascular clogging bacterium (Xylella fastidiosa) that multiplies rapidly within active plant xylem. Distinct scorch-like leaf symptoms are followed by twig and branch death leading to plant decline and death. Many other plants such as numerous shrub species and grasses become infected with BLS, but do not show symptoms and do not die.
Knowledge of BLS presently is limited, especially when attempting to understand how infection is contracted and spread within the urban environment. What is known is that the BLS bacterium is spread from diseased to healthy plant material during feeding by common urban xylem-feeding insects such as leafhoppers and treehoppers.
The disease was thought not to have significant impact in forests compared to urban environments where tree stress factors and insect vectors are distinct. However, in 2001 BLS was discovered in a New Jersey woodland area and in 2003 within the Parvin State Forest. Since this time, investigations document increasing numbers of oaks in New Jersey forested lands dying from BLS.
Courtesy of: USDA Forest Service Northeastern Area State and Private Forestry
NA-PR-05-04; (Revised August 2009)
Thousand Cankers Disease
www.thousandcankers.com — a new Thousand Canker Disease of Black Walnut website developed at Purdue University with the US Forest Service.
Thousand cankers disease (TCD) is a recently recognized disease of certain walnuts (Juglans spp.). The disease results from the combined activity of the walnut twig beetle (Pityophthorus juglandis) and a canker producing fungus in the genus Geosmithia (proposed name Geosmithia morbida). Until July 2010 the disease was only known to the western United States where over the past decade it has been involved in several large scale die-offs of walnut, particularly black walnut, Juglans nigra.