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Forest Disturbance Processes

Thousand Cankers Disease

Research Issue

Eastern black walnut tree exhibiting TCD symptoms in tree crown, Knoxville, TN.  Photo credit:  J. Juzwik, US Forest Service Northern Research StationThousand cankers disease (TCD) is a recently discovered disease of Juglans species in the United States and in Italy. Aggressive attack of susceptible Juglans by the walnut twig beetle (WTB) (Pityopthorus juglandis) is followed by development of numerous small bark cankers. The WTB carries the canker-causing fungus Geosmithia morbida that is transmitted as the insect enters the host and constructs galleries in the inner bark. Branch dieback results as numerous cankers coalesce. Multiple branch death leads to crown decline and, often, tree death. The beetle and fungus are native to Arizona, New Mexico and Mexico. The beetle appears to have “jumped” hosts from the tolerant Arizona walnut to the highly susceptible eastern black walnut (J. nigra) in New Mexico. Human-aided spread resulted in the establishment of TCD in at least two eastern states. Currently, the disease exists in nine western and six eastern states. Its discovery in the latter states led to predictions of disastrous losses of the highly valuable J. nigra within its native range, i.e. eastern North America.

Our Research

NRS scientists and their university cooperators are investigating how the insect-pathogen complex causing TCD may build and spread within the East, assessing what resistance exists in black walnut to both the pathogen and the insect pest, and evaluation of a phytosanitary treatment (vacuum-steam)  for J. nigra exports to other countries. Accomplishments of our recent research include:

  1. Assessed cold tolerance of WTB in portions of Minnesota, Wisconsin, South Dakota and Iowa,
  2. Determined the flight capacity of WTBs,
  3. Evaluated suitability of different Juglans species logs for WTB colonization and reproduction,
  4. Determined population structure of G. morbida and dissemination patterns in the United States,
  5. Discovered G. morbida on two exotic ambrosia beetle species and one native bark-colonizing weevil that had colonized TCD-symptomatic or artificially stressed trees,
  6. Discovered the co-occurrence of at least two other known canker-causing fungi (Fusarium solani and Botryosphaeria dothidea) of J. nigra on branches and stems of TCD symptomatic trees in Ohio and Tennessee, and
  7. Detected common occurrence of the insect pathogen Beauveria bassiana on WTBs in Tennessee and New Mexico and Arizona.

Expected Outcomes

Our goal is to provide scientific knowledge and contribute to TCD prevention and management guidelines for state plant regulatory officials, natural resource managers, growers of walnut for timber and nuts, and others.

Research Products

Juzwik, J.; McDermott-Kubeczko, M.; Steward, T.J.; Ginzel, M.D. 2016. First report of Geosmithia morbida on ambrosia beetles emerged from thousand cankers-diseased Juglans nigra in Ohio. Plant Disease doi: 10.1094/PDIS-10-15-1155-PDN.

Reed, S.E.; Juzwik, J.; English, J.T.; Ginzel, M.D. 2015. Colonization of artificially stressed black walnut trees by ambrosia beetle, bark beetle, and other weevil species (Coleoptera: Curculionidae) in Indiana and Missouri. Environmental Entomology 44(6):1455-1464.

Juzwik, J.; Banik, M.T.; Reed, S.E.; English, J.T.; Ginzel, M.D. 2015. Geosmithia morbida found on weevil species Stenominus pallidus in Indiana. Plant Health Progress doi: 10.1094/PHP-RS-14-0014

Zerrillo, M.M.; Caballero, J.E.; Woeste, K.; Graves, A.D.; Hartel, C.; Pscheidt, J.W.; Tonos, J.; Broders, K.; Cranshaw, W.; Seybold, S.; Tisserat, N. 2014. Population structure of Geosmithia morbida, the causal agent of thousand cankers disease of walnut trees in the United States. PLOS ONE 9(11): e112847.doi.1371/journal.pone.0112847

Utley, C.; Nguyen, T.; Roubtsova, T.; Coggeshall, M.; Ford, T.M.; Grauke, L.J.; Graves, A.D.; Leslie, C.A.; McKenna, J.; Woeste, K.; Yaghmour, M.A.; Cranshaw, W.; Seybold, S.J.; Bostock, R.M.; Tisserat, N. 2013. Susceptibility of walnut and hickory species to Geosmithia morbida. Plant Disease 97:601-607.

Van Sambeek, J.; Juzwik, J. 2010. What’s killing my walnuts – how to find help. Walnut Council Bulletin 37(1): 10-12.

Research Participants

Principal Investigators

  • Jennifer Juzwik, US Forest Service – Northern Research Station, Research Plant Pathologist
  • Robert Venette, US Forest Service – Northern Research Station, Research Biologist
  • Keith Woeste, US Forest Service – Northern Research Station, Research Geneticist
  • James McKenna, US Forest Service – Northern Research Station, Biologist

Research Partners

  • Brian Aukema, Dept. of Entomology, University of Minnesota, Associate Professor
  • Steven Seybold, US Forest Service – Pacific Southwest Research Station, Research Entomologist
  • Mark Coggeshall, Dept. of Forestry, University of Missouri, Assistant Research Professor
  • Matthew Ginzel, Dept. of Entomology, Purdue University, Associate Professor
  • Sharon Reed, Div. of Plant Sciences , University of Missouri, Research Scientist
  • James English, Div. of Plant Sciences, University of Missouri, Professor
  • Jerry Van Sambeek, US Forest Service – Northern Research Station, Research Plant Physiologist
  • Matthew Kasson, Div. of Plant Sciences, West Virginia University, Assistant Professor
  • Andrea Hefty, Graduate Research Assistant, Dept. of Entomology, University of Minnesota
  • Margaret McDermott-Kubeczko, formerly Graduate Research Assistant, Dept. of Plant Pathology, University of Minnesota
  • Tyler Stewart, Graduate Research Assistant, Dept. of Entomology, Purdue University
  • Mark Banik, US Forest Service – Northern Research Station, Microbiologist
Last Modified: February 12, 2016