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Thousand Canker Disease

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)


  • 10/29/2011 11:43 AM | Anonymous
    Since 2010 both the twig beetle and the canker fungus responsible for the disease have been found killing walnut trees in three eastern states – Tennessee (Knoxville area in July of 2010), Virginia (Richmond area in July of 2011), and in Pennsylvania (Plumstead Township, Bucks County in July of 2011). Each state has implemented internal quarantines and continues to survey surrounding areas for additional disease sites.
  • 10/29/2011 11:48 AM | Anonymous
    The Missouri Department of Agriculture enacted a state exterior quarantine to protect Missouri's black walnut resource from this newly described pest complex. This quarantine prohibits importation into Missouri of any product containng walnut bark. Several other states are enacting similar quarantines: Kansas, Michigan, Nebraska, Oklahoma, Indiana, Minnesota, North Carolina, and Wisconsin. There has been no action by the Illinois Department of Agriculture. The IFA is in discussion with state legislators to introduce similar legislation in this next session.
  • 02/08/2012 10:11 PM | Anonymous
    As of February 1, 2012, the Illinois Department of Agriculture has begun implementing a statewide ban on the transportation of most unprocessed products from walnut and butternut trees into Illinois or through Illinois from locations known to have Thousand Canker Disease infestations. There are exceptions described in A6 below.

    This ban is constituted by “regulated articles” in section A below and regulations in section B below.

    A. Regulated articles

    1) All plants, plant parts, and products of the genus Juglans; articles of Juglans, including but not limited to logs, green lumber, firewood, nursery stock, bark, mulch, burls, stumps, and packing materials;

    2) Any of the above said materials passing through a known infested state, regardless of origin;

    3) All life stages of the Walnut Twig Beetle (Pityophthorus juglandis);

    4) All life stages of the Geosmithia fungus (Geosmithia morbida);

    5) Any article, product, or means of conveyance when it is determined by the Illinois Department of Agriculture to present a risk of spread of the Walnut Twig Beetle or the Geosmithia fungus.

    6) Exceptions are nuts, nutmeat, and hulls, processed lumber (100% bark free and kiln dried, with squared edges), and finished wood products without bark, including but not limited to walnut furniture, musical instruments, and gun stocks.

    B. Regulations

    1. Regulated articles shall not be moved into Illinois any time unless:

    the regulated articles originate from an area where the Thousand Cankers Disease (TCD) complex is not known to occur, AND site of origin paperwork, demonstrating proof of harvest and COUNTY and STATE of origin, accompanies the material(s);
    the regulated articles originate from an area or transit through an area where the Thousand Cankers Disease (TCD) complex is suspected/confirmed and has accompanying phytosanitary certification demonstrating the materials have been treated by
    removal of the bark and outer 1⁄2 inch of sapwood, or
    USDA-APHIS-PPQ standards for Kiln Sterilization (T404-b-4), or Heat Treatment (T314-a), or Fumigation Treatment (T404-b-1-1);

    2. Prior to shipment, the Illinois Department of Agriculture will be notified of intended transport of any regulated materials into Illinois which originate from confirmed infested states, via an electronic version of the phytosanitary certificate;

    3. Any and all persons, businesses, or entities transferring possession of regulated articles shall inform the person, businesses, or entities taking possession of the regulated articles, either verbally or in writing, that said regulated articles are subject to State regulations;

    4. The Illinois Department of Agriculture shall be informed of any suspected TCD infested materials, and any suspected TCD infestations in standing trees.
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