Dutch elm disease is a vascular wilt disease. The earliest external symptoms of infection are often yellowing and wilting (flagging) of leaves on individual branches. These leaves often turn brown and curl up as the branches die, and eventually the leaves may drop off. Although initially only a part of the tree crown may be affected, symptoms may progress rapidly throughout the crown. Highly susceptible trees often die in a single year, but others may linger for several years. Symptoms progress quickly and death may occur rapidly in trees infected in early spring, while trees infected later in the summer may survive longer.
If the bark of infected elm twigs or branches is peeled back, brown discoloration is seen in the outer layer of wood. This discoloration in the xylem actually occurs before the foliar symptoms described above are seen; foliar symptoms result when sap flow ceases in the infected wood. Xylem browning is often discontinuous. In cross section, it appears as a circle of brown dots or a ring. Other wilt diseases of elm, such as Verticillium wilt, also cause sapwood discoloration, so positive diagnosis of Dutch elm disease depends on laboratory culturing and identification of the fungus.
Infections that take place in the spring or early summer involve “springwood” which has very long xylem vessels. In these vessels the fungi can spread rapidly throughout the tree, which then may die quickly. Later in the season, the fungi are restricted to the much shorter vessels of the “summerwood,” and the fungi spread much more slowly in the tree. Localized infections often result, and the tree is likely to survive longer.
In the absence of effective disease management, Dutch elm disease increases exponentially until an affected elm population is greatly depleted. Seedlings and many saplings escape and live long enough to reproduce, so even the most susceptible elm species have never been threatened with extinction by Dutch elm disease. Wild elm populations in the eastern and Midwestern U.S. have increased in recent decades, and this increase has led to renewed prominence of Dutch elm disease in landscapes.
If you think you have trees which are suffering from Dutch Elm Disease or any other tree disease, give Cutting Edge Tree Care Specialists a call. We are a licensed arborist with over 20 year’s experience!
Native to Asia, the hemlock woolly adelgid (Adelges tsugae) is a small, aphidlike insect that threatens the health and sustainability of eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) in the Eastern United States. Hemlock woolly adelgid was first reported in the Eastern United States in 1951 near Richmond, Virginia. By 2005, it was established in portions of 16 States from Maine to Georgia, where infestations covered about half of the range of hemlock. Areas of extensive tree mortality and decline are found throughout the infested region, but the impact has been most severe in some areas of Virginia, New Jersey, Pennsylvania, and Connecticut.
Hemlock decline and mortality typically occur within 4 to 10 years of infestation in the insect’s northern range, but can occur in as little as 3 to 6 years in its southern range. Other hemlock stressors, including drought, poor site conditions, and insect and disease pests such as elongate hemlock scale (Fiorinia externa), hemlock looper (Lambdina fiscellaria fiscellaria), spruce spider mite (Oligonychus ununguis), hemlock borer (Melanophila fulvogutta), root rot disease (Armillaria mellea), and needlerust (Melampsora parlowii), accelerate the rate and extent of hemlock mortality.
The hemlock woolly adelgid develops and reproduces on all species of hemlock, but only eastern and Carolina hemlock are vulnerable when attacked. The range of eastern hemlock stretches from Nova Scotia to northern Alabama and west to northeastern Minnesota and eastern Kentucky. Carolina hemlock occurs on dry mountain slopes in the southern Appalachians of western Virginia, North and South Carolina, Georgia, and Tennessee. Eastern hemlock is also commonly planted as a tree, shrub, or hedge in ornamental landscapes. At least 274 cultivars of eastern hemlock are known to exist.
The hemlock woolly adelgid is tiny, less than 1/16-inch (1.5-mm) long, and varies from dark reddish-brown to purplish-black in color. As it matures, it produces a covering of wool-like wax fi laments to protect itself and its eggs from natural enemies and prevent them from drying out. This “wool” (ovisac) is most conspicuous when the adelgid is mature and laying eggs. Ovisacs can be readily observed from late fall to early summer on the underside of the outermost branch tips of hemlock trees.
Cultural, regulatory, chemical, and biological controls can reduce the hemlock woolly adelgid’s rate of spread and protect individual trees. Actions such as moving bird feeders away from hemlocks and removing isolated infested trees from a woodlot can help prevent further infestations. State quarantines help prevent the movement of infested materials into noninfested areas.
To learn more about combating hemlock woolly adelgid, contact Cutting Edge Tree Care today at (800) 557-5690.
Write something about yourself. No need to be fancy, just an overview.
|Cutting Edge Tree Care Specialists||
Cutting edge tree care specialists