Once trees decline, they typically die within 2-3 years. The walnut twig beetle (WTB), Pityophthorus juglandis Blackman (Bright 1981, Wood 1982, Seybold et al. The walnut twig beetle is native to the western United States and was found in Tennessee in 2010. Emerald Ash Borer Beetle. Walnut Twig Beetle. Thousand cankers disease (TCD) is a recently recognized disease of certain walnuts (Juglans spp.). 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. Walnut Twig Beetles are so incredibly tiny and reproduce so fast that over 23,000 adults (found in just two logs) can fit in this small vial! Pictures of the walnut twig beetle can be found in our photo gallery. These beetles tunnel through the bark and carry the thousand cankers disease. The beetles seem to overwinter as adults in cavities in the trunk bark. Even though the walnut twig beetle (WTB) is likely native to Arizona, California, and New Mexico, it has become an invasive pest to economically and ecologically important walnut … The walnut twig beetle is dark brown and very tiny (1.5-2.0 mm). The walnut twig beetle appears to have made the jump, from Arizona walnut to black walnut, that was planted by eastern settlers as they relocated west. Although the beetle has been associated with dead and dying walnut trees indigenous to riparian forests of the Southwest, the primary impact appears to Life Cycle & Identification. It is smaller than a grain of rice and similar in size to a broken tip of a mechanical pencil lead. Adult beetles are metallic green and about ½” long. The walnut twig beetle was not found in any of 30 traps set in New York in 2014, the last year data is available from thousandcankers.com, a clearinghouse run … Close-up showing both larval (milky white) and adult (reddish-brown) stages of the Walnut Twig Beetle. 2011, 2017, Zerillo et al. Image. Thousand cankers disease currently threatens millions of black walnut trees in forests and urban areas. The disease results from the combined activity of the walnut twig beetle (Pityophthorus juglandis) and a canker producing fungus, Geosmithia morbida. The walnut twig beetle is native to the southwestern United States, and was first noted on Arizona walnut (Juglans major), but it is not considered to be harmful to this walnut species. The walnut twig beetle is a tiny 1 ⁄ 10-inch (1.5-1.9 mm) yellowish-brown bark beetle ().. Tunneling is almost always confined to branches 3 ⁄ 4 inch diameter and larger, including the trunk. The walnut twig beetle, a native phloem-boring bark beetle originating on Arizona walnut, has invaded urban, orchard, and native forest habitats throughout the USA as well as in Italy. The walnut twig beetle’s hard shell covers two wings, and because the beetle can fly, Geosmithia morbida is reliant on the walnut twig beetle to be spread across distances, making the fungus entomochoric, or completely dependent upon the walnut twig beetle and only found in habitats with the beetle. The native origin of thousand canker disease (Geosmithia morbida) is unknown at this point but the disease has been present in the western states since the late 90’s. 2016b) (), is a bark beetle native to the southwestern United States and northern Mexico that has been associated with a recently described fungus, Geosmithia morbida (Kolařík et al.