​Walnut Twig Beetle and Thousand Cankers Disease

Thousand Cankers Disease of Walnut

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.

TDC in Maryland:
 
Maryland Quarantine Order
On January 12, 2015, the the Maryland Secretary of Agriculture issued a quarantine order to minimize the risk of moving infested material out of the limited action area in Cecil County, and to provide confidence in Maryland walnut products moving into neighboring states from non quarantined areas. The quarantine order, map, and press release  and quarantine area map links are listed on this page under Related Information. 
 
Background
TCD was first discovered within the native black walnut range in the U.S. in 2010 in Tennessee. 
 

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.

In the 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.

In 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.

Statewide, 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 trap.

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