In known TCD areas, do not move live plant material or raw wood (branches, chips, logs, firewood, stumps, etc.) from susceptible trees.Maintaining excellent tree health by providing adequate water and good nutrition may help slow progress of the disease, but will not prevent infection or eventual death of infected trees.Do not plant susceptible species in areas where TCD is known to occur.Select non-chemical management options as your first choice! Use Integrated Pest Management (IPM) for successful plant problem management. See Walnut: Thousand cankers disease for more information. Localized staining and discoloration around the beetle tunnels may be seen in trees infected with Thousand Cankers Disease (TCD). WTB may be confused with other boring beetles, but damage by WTB is always limited to the live bark tissues. Beetle entry/exit wounds may show a small amount of staining, particularly on English walnut, but this is not consistent. Upon emergence in spring, overwintering adults fly to new sites, often in the upper limbs of host trees. Adults from late summer and fall generations are believed to overwinter in chambers they bore in the thick outer bark of trunks. Emerging adults produce a tiny exit hole in the bark, often on the underside of branches.
Larvae develop and pupate in the living tissues of the bark. Adults bore into the bark of branches (they prefer branches around 3⁄4″ in diameter and larger) and the trunk, where they feed and lay eggs. They breed and feed in the bark tissues of various species of walnut trees, including black ( Juglans nigra), Arizona ( J. major), California ( J. hindsii and J. californica), and English ( J. regia) walnuts. Adults are tiny yellow-brown beetles (around 1⁄16″ long) with lines of puncture marks along the wings. Not a great deal is known about the beetle’s life cycle, but it is believed that two or more generations may develop per growing season in warmer areas. The walnut twig beetle (WTB) is a small bark-boring beetle ( Pityophthorus juglandis) believed to be native to the southwestern US.
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