Other Invasive Species
 Box Blight or Boxwood Blight has been causing defoliation of boxwoods throughout Europe since the late 1990’s. In October, 2011, the disease was found in North Carolina and Connecticut in both nursery, and landscape plantings. The disease was also found in a Virginia nursery. Since this first US report the disease has been identified in a number of northeastern states and also in Oregon, and British Columbia. The first Maryland case of Boxwood Blight was confirmed on plants from a landscaper’s nursery in December, 2011.
The disease is caused by a fungus called Cylindrocladium pseudonaviculatum (synonym: Cylindrocladium buxicola). The first symptoms begin as leaf spots followed by rapid browning and leaf drop starting on the lower branches and moving upward in the canopy. The key symptoms that differentiate Boxwood Blight from other boxwood diseases, such as Volutella Blight and Macrophoma Leaf Spot, are numerous narrow black cankers (black streaks) that develop on the green stems. (See images below.) The pathogen does not attack the roots, so larger plants may produce new leaves during the growing season, but may lose ornamental value as defoliation becomes severe. Repeated defoliation and dieback from stem cankers has killed small rooted cuttings in nursery propagation. The causal fungus can remain in alive in fallen leaves which can then serve as the source of infection for subsequent years.
See the photos below to compare boxwood blight to volutella blight and macrophoma leaf spot. (Click on image to enlarge.)
 |
 |
 |
| Boxwood blight stem cankers - click on image to enlarge stem canker |
Volutella blight |
Macrophoma leaf spot |
 The spores of the fungus can be splash-dispersed through irrigation or rainfall resulting in spread of the disease within a plant or to nearby boxwoods. The primary method of long distance disease spread is most likely shipping of infected plants, use of contaminated tools and transport vehicles that contain fallen infected leaves.
American, English and Korean boxwoods are all susceptible to this new disease although some variation in disease severity among cultivars has been reported. Sweet box, Sarcococca, an ornamental that is in the boxwood family (Buxaceae) has been infected under experimental conditions. Research is under way to test the effectiveness of fungicides for management of Boxwood Blight.
If you suspect you see boxwoods infected with this new disease in landscapes, please call our toll free number (800-342-2507) and speak to a horticulture consultant.
For more information, see Boxwood Blight - A new disease for Connecticut and the US and NC pest alert box blight.
Euonymus leaf notcher, Pryeria sinicia, is a recent pest of Euonymus in Maryland. Please visit the Maryland Invasive Species Council Web Site for details at http://www.mdinvasivesp.org/pryeria_sinica.html
 |
 |
Pryeria sinica moths and eggs
on Euonymus |
Pryeria sinica caterpillars feeding on Euonymus |
 Wavyleaf Basketgrass,
Oplismenus hirtellus ssp. undulatifolius, is a highly invasive grass that has been discovered in several areas in Maryland including parts of Patapsco State Park. The seeds are very sticky and can be moved around easily by people and animals. Keep an eye out for it. For information and to report sightings visit the Maryland Department of Natural Resources information page at: http://dnr.maryland.gov/wildlife/plants_wildlife/wlbg/index.asp
European wood wasp, Sirex noctilio, has been discovered in upstate New York and Canada along the St. Lawrence Seaway. It has the potential t be a very serious pest of pines in the U.S. Please read more about this serious new threat at http://pestthreats.umd.edu/content/documents/SWWBulletin.pdf
Thousand Cankers Disease - Originally found only in western states, a recent report from Knoxville Tennessee confirmed that Thousand cankers disease of walnut has become established in that area. This new finding suggests that the walnut twig beetle was introduced and established in Tennesee a very long time ago. How it got there is still a mystery, but hopes of keeping this disease confined to western states is now not possible. Infested wood may have been transported out of Tennessee to other eastern states for years. Alerts are being sent out and several states are now considering initiating surveys for initial symptoms. 
The walnut twig beetle is reddish-brown and 1.5 to 1.9 millimeters long (Fig. 1). The disease is spread by this beetle when it makes galleries under the bark. The fungus causes the tissue to die disrupting the trees’ ability to take up water. The beetles entrance holes into the black walnut aren’t much bigger than a pin hole. While it’s unlikely you will see the insect, its damage is more obvious. To scout for symptoms look first in black walnut trees with existing crown dieback. Then look for individual branches that show flagging with either yellowing leaves remaining attached or leaves that have collapsed and wilted (Fig. 2). The latter is a somewhat stronger possible symptom. Then try to collect a dead or dying limb and look for the minute exit holes.
 |
Fig. 2 - Walnut leaves that have collapsed
and wilted |
When branches are peeled carefully, the exit holes will have associated larval galleries (Fig. 3). This can be considered confirmation of this disease since the damage caused by the walnut twig beetle, Pityophthorus juglandis will be closely associated with the fungus Geosmithia morbida which causes thousand cankers disease (Fig. 4). The best size for looking for evidence of colonization is walnut branches 1-2 inches in diameter.
 |
 |
Fig. 3 - Walnut twig beetle galleries under the bark of an infested tree |
Fig. 4 - Walnut twig beetle galleries under the bark of an infested tree showing evidence of canker disease |
If you find black walnut trees with suspicious symptoms please call HGIC (1-800-342-2507) or e-mail the location, description and photos to HGIC so we can alert the Maryland Department of Agriculture about this disease in Maryland.
For additional information read USDA's Thousand Cankers Disease Pest Alert Fact Sheet and Colorado State’s Thousand Cankers Disease website.
 Asian Longhorned Beetle (ALB), Anoplophora galbripennis, is a very serious exotic pest that was introduced in solid wood packing material from China. It has the potential to cause more damage than Dutch elm disease, chestnut blight and gypsy moths combined. The beetle was first detected in Brooklyn, NY in 1996. It has since been discovered in Chicago (1998), Jersey City, NJ (2002), Borough of Carteret, NJ (2004), Prall’s Island (near Staten Island), NY (2007), and in Worcester, Massachusetts. (2008) and most recently in Bethel, OH.
Adult ALB are usually large, distinctive-looking insects measuring 1- to 1-1/2 inches long, not including antennae. Their white-banded antennae can be as long as the body itself in females and almost twice the body length in males.
Signs of infestation include perfectly round exit holes (about 3/8 to 1/2 inch in diameter) made by adult beetles when they emerge from trees; the pockmarks on tree trunks and branches where female beetles deposit eggs; frass (wood shavings and saw dust) produced by larvae feeding and tunneling; early fall coloration of leaves or dead branches, and running sap produced by the tree at the egg laying sites, or in response to larval tunneling.
In the U.S., Asian longhorned beetle is known to attack 29 species of deciduous hardwood trees. ALB prefers species of maple (Acer spp.) including boxelder, Norway, red, silver, and sugar maples. Other known hosts include alders (Alnus spp.), birches (Betula spp.), elms (Ulmus spp.), horsechestnut (Aesculus spp.), poplars (Populus spp.), sycamore (Platanus spp.) and willows (Salix spp.)
For additional information see:
|
