Branch end of black walnut showing the alternate arrangement of its large compound leaves. 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. Description. Click on a photo to get started: Plant Heroes is brought to you by the American Public Gardens Association's Plant Protection Program and made possible with support from the U.S. Forest Service. The walnut twig beetle, in association with the fungus, Geosmithia morbida, causes the insect-pathogen complex known as “thousand cankers disease,” which wreaks havoc on walnut trees. ; Thousand Cankers Disease spores: Alan Windham, University of Tennessee, Bugwood.org. Description. Cross section of a black walnut twig showing the unique chambered sections inside the twig. Close-up of walnut branch showing the early stages of canker development around beetle tunnels. Thousand Cankers Disease is caused when Walnut Twig Beetles, which carry a fungus (Geosmithia morbida), tunnel beneath the bark of walnut trees, causing small cankers to form. Walnut twig beetle (WTB), Pityophthorus juglandis, (Figure 1) is a small native phloeophagous (phloem-feeding) insect that has recently been associated with the fungus . ; Larva, adult, beetle galleries: Whitney Cranshaw, Colorado State University, Bugwood.org. ; Twig lobes,black walnut fruit: Rob Routledge, Sault College, Bugwood.org. 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. of Agriculture, Salem, OR; 2 USDA Forest Service, Forest Health Protection, Arlington, VA . Walnut twig galleries and cankers: Ned Tisserat, Colorado State University, Bugwood.org; Size comparison to penny: Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org. ; Cultured colony of thousand cankers disease: Ned Tisserat, Colorado State University, Bugwood.org. The insect, measuring about 1.5 millimeters long, is smaller than a grain of rice. They resume activity by late-April and most fly to branches to mate and initiate new tunnels for egg galleries. The young fruit of the black walnut is light green, round, and 2- 2 1/2 inches (5-6 centimeters) across. Adult beetles are small, approximately 1/16 inch long, and reddish-brown. Black walnut tree in decline from Thousand Cankers Disease and showing dieback in the upper canopy. Steve was highly committed to investing time and energy into young scientists. “I would not be studying forest entomology if not for him, and I am incredibly grateful he introduced me to my life’s passion. Walnut Twig Beetle. Thousand cankers disease " was given its name because of the magnitude of galleries and subsequent cankers created by the disturbance regime of walnut twig beetles and Geosmithia morbida . ; Grove: Robert Vidéki, Doronicum Kft., Bugwood.org. He was a researcher at the Pacific Southwest Research Station, USDA Forest Service, Davis, and a lecturer and researcher with the UC Davis Department of Entomology and Nematology and mentored students. ; Top view, side view: Steven Valley, Oregon Department of Agriculture, Bugwood.org. In 2012 the fungus was found in Butler county, Ohio. The insect, measuring about 1.5 millimeters long, is smaller than a grain of rice. ; Black walnut tree: Vern Wilkins, Indiana University, Bugwood.org. Walnut twig beetles are very small, about 1/16 inch (1.5 mm), reddish-brown bark beetles that bore through the outer bark and into the phloem of the branches and main stems of walnut trees. Seybold at UC Davis and the USDA Forest Service. Yet another example of how complex and advanced the insect olfactory system is! Spores (tiny structures that carry reproductive information to form a new fungus) of Geosmithia morbida. Before Image. ; Black walnut leaves: Paul Wray, Iowa State University, Bugwood.org. During tunneling, the Geosmithia fungus is introduced and begins growing in the tree’s wood. Walnut Twig Beetle. These papers highlight sources of and provide an ecological context for potential nonhost, volatile compounds that may be of use in semiochemical repellents to protect walnut trees from attack by P. juglandis.”, “Steve was a giant in the forest entomology community, particularly in the field of bark beetle chemical ecology,” Audley said. Display Order. WALNUT TWIG BEETLE - A trapping survey was conducted in 17 counties to detect to the walnut twig beetle component of thousand cankers disease (TCD). The insect, measuring about 1.5 millimeters long, is smaller than a grain of rice. The walnut twig beetle, in association with the fungus, Geosmithia morbida, causes the insect-pathogen complex known as “thousand cankers disease,” which wreaks havoc on walnut trees. It is the only Pityophthorus species associated with Juglans but can be readily distinguished from other members of the genus by 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. This tiny beetle and the fungus it carries can greatly affect black walnut trees, a valuable source of wood and delicious nuts! “Together, both studies provide strong evidence for directed flight host searching and in-flight, host discrimination behaviors by Pityophthorus juglandis. “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. Easy to use; For best results, use with Walnut Twig Beetle Lindgren 4-Funnel Trap w/ Wet Collection Cup; Ongoing research on lure improvement and use. 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). These beetles carry a fungus that causes damage to the trees and can even kill them. As these cankers grow together they stop the flow of water and nutrients in the branch and dieback occurs. 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. This shows the beetle has evolved to be highly tuned into its environment and the volatile profiles of its host species. Highly magnified side view of the Walnut Twig Beetle (Pityophthorus juglanddis). ; Chambered pith, flower spikes: Paul Wray, Iowa State University, Bugwood.org. Walnut Twig Beetle Lure Features. What should we learn about first? Adults emerge to produce a second generation. Future work may focus on identifying repellent chemical compounds released by the non-host tree species included in our studies.”, “Not only was Steve a giant in the forest entomology community, but he was a giant in my life,” Homicz commented. In the Southwest it attacks Arizona walnut. Trapping methods and guidlines have been developed by a team on entomologists led by S.J. 2011). Black walnuts grow to be a medium to large tree up to 100 feet in height and usually have a straight trunk and narrow crown under competition in the forest. They resume activity by late-April and most fly to branches to mate and initiate new tunnels for egg galleries. Click to Download PDF Version of Field Guide. Identification. 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. Close-up of bark showing small piles of sawdust created by beetle tunneling. ; Adults on penny, vial: Whitney Cranshaw, Colorado State University, Bugwood.org. ; Bark: Jason Sharman, Vitalitree, Bugwood.org. 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. This disease is the result of the combined activity of a fungus, Geosmithia morbida, and the walnut twig beetle … Bug. Category Image. 0. This fungus and WTB are the principal agents involved in thousand cankers disease (TCD) (Seybold et al. After Image. Image. “He was a great mentor and I am fairly confident I would not be half the scientist I am today without his guidance.”, Said Homicz: “Our papers highlight that the walnut twig beetle is highly skilled at discerning hosts in flight. The beetle is native to Arizona, California, New Mexico, and northern Mexico. 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