Thousand Canker Disease (TCD) is the result of a tiny bark beetle which burrows in the bark and creates large and multitudinous galleries, making these trees susceptible to fungal disease and canker formation by creating an entry point in the bark. TCD earned its name from the huge number of cankers associated with dead limbs and leaders. The main culprits involved in the dieback of these trees are the walnut twig beetle (Pityophthorus juglandis) and a newly identified fungus Geosmithia morbida, both of which have only been found occurring on walnut species and a closely related species Pteryocarpa sp., the wingnut tree. Afflicted trees usually die within 3 years of infestation.
This October the Maryland Department of Agriculture confirmed the presence of TCD on black walnut trees in Cecil County, Maryland. Bait logs were collected from a trap site and inspected for signs of the beetle and fungus and a positive confirmation was obtained from the U.S. Forest Service on October 6, 2014. Follow-up DNA sequencing is being performed on isolated culture samples.
This finding brings the number of states with TCD infestations up to 16, including; AZ, CA, CO, ID, IN, MD, NC, NM, NV, OH, OR, PA, TN, UT, VA, and WA. Phytosanitary quarantine sites for affected trees exist within 16 states, 6 of which have both internal and external regulations. AR, IL, KS, MI, MN, MO, NE, OK, WI, and WV all have external quarantine sites, while IN, NC, OH, PA, TN, and VA have both internal and external quarantines in place. Dispersal season is coming to a close with the advent of winter weather and with it 2014’s annual TCD survey in the eastern region is wrapping up.
Thousand Cankers Disease was reported in Italy for the first time in 2013 on a small number of black walnut trees. This species is broadly distributed across Europe and so the disease poses a great risk economically, aesthetically and environmentally. The fungus G. morbida and its vector beetle, P. juglandis were both added to the European and Mediterranean Plant Protection Organization alert list.
Identification and monitoring are the extent of management for TCD at this point. If you suspect that any of your landscape trees or town trees have thousand cankers disease contact you arborist, visit http://www.savatree.com/tree-service.html, and get in touch with your state’s branch of the National Plant Diagnostic Network (NPDN). The NPDN has a clinic in every state, more information on disease identification and control visit their website at www.npdn.org.