Both papers list Seybold, a pioneering scientist in the study of the beetle and the newly discovered disease that it causes, as a co-author. Before Image. In the Southwest it attacks Arizona walnut. Yet another example of how complex and advanced the insect olfactory system is! Even when we attempt to lure them to non-host trees by tricking them with aggregation pheromone, more often than not, they correctly identify their host tree. Exit holes: Karen Snover-Clift, Cornell University, Bugwood.org. 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. Peak flight activity of adults occurs from mid-July through late August and declines by early fall as the beetles enter hibernation sites. Dark staining caused by Geosmithia cankers in black walnut. Close-up showing both Walnut Twig Beetle larva and the white powdery spores of the Geosmithia fungus that causes the tree to develop cankers and die. Colony of the fungus, Geosmithia morbida, that causes Thousand Cankers Disease. Walnut Twig Beetle. Walnut twig beetle (WTB), Pityophthorus juglandis, (Figure 1) is a small native phloeophagous (phloem-feeding) insect that has recently been associated with the fungus . The beetles seem to overwinter as adults in cavities in the trunk bark. Adult beetles spend the winter within cavities excavated in the bark of the trunk. The walnut twig beetle is native to North America, being originally described in 1928 based on specimens collected in the area of “Lone Mountain”, New Mexico (Grant County). TCD results from the combined activity of Geosmithia morbida fungus and the walnut twig beetle (WTB, Pityophthorus juglandis). 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. Take a virtual field trip to get to know some interesting species. The beetle is the vector of a fungus that causes Thousand Canker Disease (TCD), an accumulation of many small branch and stem cankers that can kill an infected tree. Kathy Keatley Garvey/Courtesy photo. A Screening Aid for the Identification of the Walnut Twig Beetle, Pityophthorus juglandis Blackman James R. LaBonte1, Robert J. Rabaglia2 1 Plant Division, Oregon Dept. “Together, both studies provide strong evidence for directed flight host searching and in-flight, host discrimination behaviors by Pityophthorus juglandis. Close-up of galleries created by Walnut Twig Beetle tunneling under the bark. The walnut twig beetle is commonly associated with the fungus Geosmithia morbida that causes damage ranging from discoloration in some species of walnuts to mortality in others. " The walnut twig beetle Pityophthorus juglandis is a minute (1.5-1.9 mm) yellowish-brown bark beetle, about 3X long as it is wide. The beetle is native to Arizona, California, New Mexico, and northern Mexico. Two forest entomologists who studied with the late chemical ecologist Steven Seybold, a UC Davis department of entomology and nematology associate, have published two complementary papers on the walnut twig beetle that shed more light on the invasive pest. Trapping methods and guidlines have been developed by a team on entomologists led by S.J. Spores (tiny structures that carry reproductive information to form a new fungus) of Geosmithia morbida. Identification. They resume activity by late-April and most fly to branches to mate and initiate new tunnels for egg galleries. The walnut twig beetle is native to Arizona, California, and New Mexico; however the beetle and fungus have been found in eastern states. Originally a problem in warmer climates, this pest has moved into Ohio and the surrounding colder states, causing the potential onset of walnut tree extinction. Walnut has large compound leaves (12-24 inches long) each of which has 10 to 24 leaflets. During tunneling, the Geosmithia fungus is introduced and begins growing in the tree’s wood. Steve was highly committed to investing time and energy into young scientists. Close-up of bark showing small piles of sawdust created by beetle tunneling. Walnut Twig Beetle Lure Features. During tunneling, the Geosmithia fungus is introduced and begins growing in the tree’s wood. The insect, measuring about 1.5 millimeters long, is smaller than a grain of rice. 2011). ; Cultured colony of thousand cankers disease: Ned Tisserat, Colorado State University, Bugwood.org. * “Walnut Twig Beetle Landing Rates Differ Between Host and Nonhost Hardwood Trees under the Influence of Aggregation Pheromone in a Northern California Riparian Forest” (https://doi.org/10.1111/afe.12410). Cross section of a black walnut twig showing the unique chambered sections inside the twig. Highly magnified top view of the Walnut Twig Beetle (Pityophthorus juglandis). The young fruit of the black walnut is light green, round, and 2- 2 1/2 inches (5-6 centimeters) across. This shows the beetle has evolved to be highly tuned into its environment and the volatile profiles of its host species. “The first study is one of few bark beetle host selection studies conducted without the use of semiochemical lures,” said Audley, now a postdoctoral fellow funded by Oak Ridge Laboratories and based at the USDA Forest Service, Pacific Southwest Research Station, Davis. of Agriculture, Salem, OR; 2 USDA Forest Service, Forest Health Protection, Arlington, VA . Close-up of flower spikes on a black walnut tree. ; Larva, adult, beetle galleries: Whitney Cranshaw, Colorado State University, Bugwood.org. Adult beetles spend the winter within cavities excavated in the bark of the trunk. Wood staining: Ned Tisserat, Colorado State University, Bugwood.org. The husk of the walnut fruit turns black as it ripens in late summer to fall. The walnut twig beetle Pityophthorus juglandis is a minute (1.5-1.9 mm) yellowish-brown bark beetle, about 3X long as it is wide. 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