Thousand Cankers Disease

Thousand cankers disease (TCD) is the result of an insect/disease complex involving the walnut twig beetle and a canker fungus (see below) that recently has been killing planted eastern black walnut in a number of western states since at least 2001. The complex obviously posed a serious threat to the eastern black walnut resource if transferred east of the Great Plains. Since 2010, however, both the twig beetle and the canker fungus responsible for the disease have been discovered 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.

General information on TCD can be found at:

• http://www.na.fs.fed.us/pubs/detail.cfm?id=5225
  

Information on TCD in individual states:

Posted on the Tennessee Department of Agriculture/Tennessee Division of Forestry web site at:

• http://www.tennessee.gov/agriculture/regulatory/tcd.html

Posted on the Virginia Department of Agriculture and Consumer Services web site at:

• http://www.vdacs.virginia.gov/news/releases-b/072111tcd.shtml

Posted on the Pennsylvania Department of Agriculture web site at:

• http://www.agriculture.state.pa.us/portal/server.pt/community/pennsylvania_
  department_of_agriculture/10297

Information on the complex as it has occurred in the western US can be found at these and other postings on the web:

• http://www.ext.colostate.edu/pubs/insect/0812_alert.pdf
• http://www.denvergov.org/Portals/626/documents/
• http://mda.mo.gov/plants/pests/thousandcankers.php

While this disease poses a serious threat to black walnut in its native range, it is not yet known how damaging the twig beetle/canker fungus will be to native black walnut under eastern conditions, or how fast it may spread. The beetle (Pityophthorus juglandis) is native to the southwestern US and Mexico. The canker fungus, Geosmithia sp. nov. (proposed species name is morbida), is new to science and to date is only known in association with the beetle; however, it is a relatively non-aggressive fungus that only has a serious affect in a tree after thousands of individual beetle attacks (inoculation points), hence the common name for this malady. The newly-discovered infestations above appear to be at least several-to-many years old.

It is now imperative that eastern black walnuts recently dead or with fading foliage, dying twigs and branches, be carefully examined and sampled for the presence of the beetle and fungus. It is particularly important that qualified experts be consulted when this is done. Samples need to be carefully handled and sent only to laboratories which are authorized to handle such specimens and have the expertise to identify these agents. If in doubt about who to call or consult, check first with your State Forestry Agency or State University Extension Service.

Unfortunately, definitive control and management recommendations are not available. However, tree/forest owners can help minimize the chances of spreading TCD further:

• Investigate dying/dead walnuts thoroughly and report suspected TCD to state forestry or extension agents.
• Obtain expert assistance when collecting and sending samples for diagnosis; if in doubt don't send or transport walnut material off-site.
• Don't transport dead/dying walnut wood, branches or twigs off-site unless TCD is known not to be present.
• Prompt tree removal and proper debris disposal may help to limit the further spread of TCD; obtain proper disposal instruction from qualified experts if TCD is diagnosed. Beetles can emerge by the thousands from any dead and dying wood pieces. Destruction by burning or burying is probably the only sure way to prevent this. Chipping often results in wood pieces still large enough to allow beetles to emerge and spread TCD. Covering infested wood with plastic or other material is not sufficient as beetles will chew their way out.
• The beetles and fungus are restricted to the tree bark so consider the movement of any bark materials from dead or dying trees as the highest risk for additional disease spread
• Don't transport walnut as firewood. Use local sources of wood when camping.
• TCD is not federally-regulated but be aware that individual states have enacted state- or county-level quarantines restricting the movement of untreated walnut materials of all kinds; obtain information on these from state authorities before moving, buying, or selling any walnut wood or material.

Officials in many other eastern states with walnut resource are conducting detection surveys, particularly in areas of potential introduction.

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USDA Forest Service - Forest Health Protection, Southern Region
Last Modified:  Thursday, 01 September 2011 at 16:15:12 EDT