The Maryland Department of Agriculture (MDA) has implemented a quarantine that makes it illegal to move walnut material and hardwood firewood out of a 21-square-mile area in the northeast corner of Cecil County. This area is bounded by both the Pennsylvania and Delaware state lines. They’re serious about this: Violations could result in criminal or civil penalties.

Thousand cankers disease of walnut, vectored by the walnut twig beetle.Photos courtesy of Whitney Cranshaw, Colorado State University; 

What’s the fuss? Thousand cankers disease was confirmed in the Fair Hill Natural Resource Management Area, where surveillance traps had been set to detect the leading culprit: walnut twig beetle. The trap site where a beetle was discovered has tested positive for the beast for the past two years; the fungus the beetle transmits was detected in 2014 in trap logs set by the MDA. To date, this is the only confirmed incident in the state, and MDA officials believe it is an isolated infestation.

Thousand cankers disease is actually a disease complex, native to the Western U.S., that is the result of the combined activity of the Geosmithia morbida fungus and the walnut twig beetle, Pityophthorus juglandis. It primarily affects black walnut (Juglans nigra).