Thousand cankers disease (TCD) is a disease complex native to the western United States and 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. 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 2015 quarantine order has been updated to include all of Baltimore City and part of Baltimore County [PDF, 1.2 MB]. The new quarantine [PDF, 1.0 MB] was signed on May 1, 2019 by the Maryland Secretary of Agriculture.