Thousand cankers disease (TCD) is a disease complex native to the western United States that primarily affects black walnut, Juglans nigra. This disease is the result of the combined activity of a fungus, Geosmithia morbida, and the walnut twig beetle (WTB) Pityophthorus juglandis.
Thousand cankers disease currently threatens millions of black walnut trees in forests and urban areas. Black walnut is an important species with great economic and ecological value throughout its native range. TCD is not federally regulated. Several states have established quarantines in an attempt to prevent the disease from spreading.
2014, the positive trap was reset on April 1 and checked every two weeks from spring
into the late fall. This trap was taken
down on December 2, 2014. Eighteen WTB were collected. To try to
determine the extent of the WTB infestation, 12 pheromone baited traps were
deployed near the initial positive trap. Thirteen traps in total were deployed in Fair Hill NRMA. Statewide, 43 pheromone baited traps were deployed in 2014. Only the original positive trap was positive
for WTB. At this same site, bait logs were deployed in
2014. These logs were black walnut
branches about 1.5 inches in diameter and 12 inches in length and baited
with WTB pheromone. On October 6, 2014, USDA-FS and the University of Minnesota confirmed
the presence of Geosmithia morbida –
the pathogen that causes TCD - from one of the logs.
A quarantine has been issued by
MDA to minimize the risk of moving infested material out of the
limited action area, and to provide confidence in Maryland walnut products
moving into neighboring states. In addition, Fair Hill NRMA agreed to discontinue the firewood cutting program.
In 2018, forty-nine (49) traps were set in 18 counties across Maryland for detection. Thirteen (13) traps were set in Cecil County for delimiting. Trap CE01 was again positive for WTB in 2018. Four (4) traps were set near a positive site discovered in Baltimore City by Plant Protection in an exotic wood boring beetle survey in 2017. Traps BC01, BC02, BC03, and BC04 were also positive for WTB. Branch samples taken from the tree at BC04 were also positive for TCD. Initial identification of WTB in trap samples was made by Lawrence Barringer, PDA entomologist. Specimens were confirmed by Dr. Robert Brown APHIS PPQ Domestic Identifier at Purdue University Geosmithia morbida (TCD) was detected by Jennifer Juzwik, Pathologist USFS NRS, and confirmed by DNA analysis by her Research Associate, Anna Yang, UM. Trees at the original positive site have not shown evidence of decline as of yet.
50 Harry S. Truman Parkway, Annapolis, MD 21401