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Health Alert

This (Forest) Health Alert Blog allows the IFA to post information about extremely serious forestry diseases and insect pests to trees.  Each pest or disease will have its own posting and status will be added as comments to the post. The website's administrators will be allowed to post comments to this blog, while everyone will be able to read all posts and comments.  There is much more information on hardwood pests and diseases as well as invasive plants in the Members' Section.

  • 05/23/2011 7:44 AM | Anonymous
    From the USDA Forest Service's Forest Health Program:

    Gypsy moth, a non-native invasive species introduced into Massachusetts 135 years ago, has spread southwest and now is established in about one third of the potentially susceptible habitat in the United States. Defoliation caused by gypsy moth caterpillars may cause tree mortality, affect human health and be a nuisance. When gypsy moths first move into an area, there are significant impacts for the first 10-20 years. In areas that have had gypsy moth for many years, such as the Northeast, forests have recovered. The USDA national gypsy moth program has three strategies: Eradication, slow-the spread and suppression. The program will refocus in 2007 to accrue cost savings which will be used for other higher priority pests such as Sirex noctilio, emerald ash borer and other invasive species.
    • Eradication continues to be the focus of the national gypsy moth management strategy. This vigilance and quick action has kept gypsy moth out of the western US.
    • In FY 2007, Slow-the-spread will be reoriented to focus on the highest priority area, while fully implementing the program. Gypsy moth spread has been reduced by 50% along a 1,000 mile front from North Carolina to Wisconsin.
    • In FY 2007, suppression efforts in the area that has had gypsy moth for many years will be reduced to focus on other higher priority pests and areas that have recently become infested with gypsy moth.

    The gypsy moth, Lymantria dispar, is one of North America's most devastating forest pests. The species originally evolved in Europe and Asia and has existed there for thousands of years. In either 1868 or 1869, the gypsy moth was accidentally introduced near Boston. About 10 years after this introduction, the first outbreaks began in Boston and in 1890 the State and Federal Government began their attempts to eradicate the gypsy moth. These attempts ultimately failed and since that time, the range of gypsy moth has continued to spread. Every year, isolated populations are discovered beyond the contiguous range of the gypsy moth but these populations are eradicated or they disappear without intervention. It is inevitable that gypsy moth will continue to expand its range in the future.

    The gypsy moth is known to feed on on the foliage of hundreds of species of plants in North America but its most common hosts are oaks and aspen. Gypsy moth hosts are located through most of the coterminous US but the highest concentrations of host trees are in the southern Appalachian Mtns., the Ozark Mtns., and in the northern Lake States.

    Gypsy moth populations are typically eruptive in North America; in any forest stand densities may fluctuate from near 1 egg mass per ha to over 1,000 per ha. When densities reach very high levels, trees may become completely defoliated. Several successive years of defoliation, along with contributions by other biotic and abiotic stress factors, may ultimately result in tree mortality. In most northeastern forests, less than 20% of the trees in a forest will die but occasionally tree mortality may be very heavy.

    Forest Effects

    Despite over 100 years of presence in North America, researchers are still at a loss to explain and predict the extent of the changes in forest vegetation likely to take place through gypsy moth disturbance. A major concern is the potential loss of economically critical and ecologically dominant oak species (Quercus, spp.). Most studies of forest compositional changes with gypsy moth defoliation indicate that less susceptible species will dominate the forest, so in effect, forests may have fewer gypsy moth problems in the future.

    Natural Enemies

    A variety of natural agents are known to kill gypsy moths in nature. These agents include over 20 insect parasitoids and predators that were introduced over the last 100 years from Asia and Europe. Small mammals are perhaps the most important gypsy moth predator, especially at low population densities. Birds are also known to prey on gypsy moths but at least in North America this does not substantially affect populations. A nucleopolyhedrosis virus usually causes the collapse of outbreak populations and recently an entomopathogenic fungus species has caused considerable mortality of populations in North America.


    Over the last 20 years, several millions of acres of forest land have been aerially sprayed with pesticides in order to suppress outbreak gypsy moth populations. Though some areas are treated by private companies under contract with land owners, most areas are sprayed under joint programs of state governments and the USDA Forest Service. Your local extension service can provide more detailed information about programs in your area.

    The USDA, State and local governments also jointly participate in programs to locate and eradicate new gypsy moth populations in currently uninfested areas. Most of these projects focus on populations of European origin, but recently several Asian populations have been discovered and eradicated in the US and Canada.

    In 1992, the USDA Forest Service began a pilot program to test the feasibility of slowing the spread (STS) of the gypsy moth in North America. STS pilot programs currently exist in North Carolina, Virginia, West Virginia, and Michigan.


    The gypsy moth has been intensively studied over the last 100 years in North America. Currently there are numerous groups around the country investigating various aspects of the biology, ecology, and management of the gypsy moth. This work is funded by the USDA Forest Service, the USDA Agricultural Research Service, the USDA Cooperative State Research Service, the USDA Animal and Plant Health and Inspection Service, and numerous state and private Universities.

    Map of Gypsy Moth Quarantine Areas by County

  • 05/23/2011 7:22 AM | Anonymous
    This is a brief overview of the black walnut disease called Thousand Cankers.  Since there are no confirmed reports of this disease in Illinois this is a precautionary notice.

    This disease kills black walnut trees by destroying the phloem thereby stopping the flow of nutrients.   It was first described in early 2008 by researchers at Colorado State University, but is thought to have been infecting and killing walnut trees for at least a decade.  The disease had only been found in the western United States until July 2010 when an outbreak was confirmed in Knoxville, Tennessee.

    Thousand Cankers disease is caused by the fungus Geosmithia (morbida) which is carried by the adult walnut twig beetle.  The beetle burrows into a twig carrying the fungus; the fungus forms a canker which expands over time.  Each beetle wound causes another canker.  As the tree becomes stressed with the expanding cankers, more beetles are attracted.  It is death by a thousand cankers.

    Because the cankers are buried in the phloem, there is no outward sign of disease.  Early yellowing of the exterior crown, followed by leaf wilting of large limbs, marks the end of the tree.  Susceptible walnuts die within two or three years of leaf yellowing.

    For a more complete description, go to this Wikipedia article

    or the Colorado State University website

    It is possible that the disease has been present for years with researchers just recently able to identify the fungus agent and its relationship with the twig beetle.  A proposed theory for the disease origin is that the slow-growing Arizona walnut, which are fairly resistant, harbored the disease.  As the eastern black walnut was introduced in western states, it fell prey due to its faster growth.

    The disease progresses slowly when introduced into an area, it is thought that the Knoxville infestation may have started over a decade ago.  That said, there may be other unreported infections in the eastern US.

    Researchers currently do not know how long a tree has to live once infected.  It could take more than a decade.  Certainly, vigorously growing trees planted on good walnut sites will be more resistant.

    There are no known spraying techniques that have been proven to control the walnut twig beetle.  But there are two things you can do.  

    1) Do not bring any walnut wood onto your land - logs, burls, firewood, mulch, or even packing material.  The beetle survives on wood for up to 3 years after trees are cut, and can even survive chipping.  At present, there are no reports that nursery stock is a vector.

    2) Favor dominant, vigorously growing walnuts in your stand management.  Walnuts losing the competition with other crop trees or older walnuts exhibiting slower growth could be stressed and therefore susceptible to disease. Consider harvesting them.

    Download the USDA Forest Service Thousand Canker Disease Field Guide.

    The video below was provided by the Virginia Department of Agriculture.  It is a good overview of the symptoms of this disease and how to spot the walnut twig beetle entry/exit holes and then expose the underlying camkers.  The video is a little over five minutes in length.


    As of 2/1/2012, the Illinois Department of Agriculture has instituted a ban on movement of walnut products into or through the state.  You can read about the specifics of the ban in the third comment below.  There are three (3) documents associated with this ban:
    a) the Governor's Proclamation - Download here (279 KB)
    b) a description of the disease and its extent - Download here (2.9 MB)
    c) a compliance certificate - Download here (148 KB)
  • 05/18/2011 8:21 PM | Anonymous
    The Asian longhorned beetle (ALB) is an exotic pest threatening these tree species:
    • genus acer - maple and boxelder
    • genus salix - willow
    • genus ulmus - elm
    • genus aesculus - horsechestnut, buckeye
    Adults are large (0.75 - 1.50 inches long) with very long black and white banded antennae.  The body is glossy black with irregular white spots.  Adults can be seen from late spring to fall depending on the climate.

    As of July, 2006, the quarantine areas were lifted in Illinois after no more infestations were found.
  • 05/18/2011 7:44 PM | Anonymous
    From the Emerald Ash Borer website ( ): 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. Emerald ash borer is also established in Windsor, Ontario, was found in Ohio in 2003, northern Indiana in 2004, northern Illinois and Maryland in 2006, western Pennsylvania and West Virginia in 2007, Wisconsin, Missouri and Virginia in summer 2008, Minnesota, New York, Kentucky in the spring of 2009, Iowa in spring of 2010, and Tennessee in the summer of 2010.

    What to know about EAB:

    Where is it:

    Go to this website for regional and state maps of EAB confirmed sightings.

    Also, the Illinois Department of Agriculture has established THIS PAGE for information on EAB within the state.

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