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.
In 2011, MDA's Forest Pest Management Section visually
surveyed for TCD. No visual signs were observed. In 2012, the visual
inspection continued and 28 pheromone baited traps were deployed throughout
Maryland. No visual signs of TCD were
observed and no WTB were collected.
summer of 2013, MDA visually surveyed 248 areas and no visual signs of TCD were observed. At the same time, 29 pheromone traps were
deployed throughout Maryland (see map).
All traps were negative except one in Cecil County in the Fair Hill Natural
Resource Management Area (NRMA). All
four collections from this trap were positive for WTB. The identification was
confirmed (on January 6, 2014) by Joel Floydo Domestic Diagnostic Coordinator, USDA Animal and Plant
Health Inspection Service. A total of 30 WTBs were collected. Visual evidence of TCD was not noted. Branch samples collected on December 19, 2013 were analyzed and TCD
was not detected. Several times during
the winter of 2013/2014 additional branch samples were taken and TCD was not detected.
During a meeting on January 27, 2014, MDA's Forest Pest Management and Plant Protection sections along with the Maryland
Department of Natural Resources and University of Maryland Extension decided not to create a quarantine but to attempt to determine
the extent of the infestation and to continue trying to detect the disease. The Manager of Fair Hill NRMA agreed to discontinue the fire wood cutting program.
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 December 2, 2014. Eighteen WTB have
been 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. Only the original positive trap is 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. In October 6, 2014, USDA-FS and 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.
43 pheromone baited traps were deployed in 2014 including 12
traps in Fair Hill to determine extent of infestation and 29 traps
statewide including the original positive trap. All of these traps were negative for WTB except the original positive
50 Harry S. Truman Parkway, Annapolis, MD 21401