Managing Thousand Cankers Disease in High-value Plantings of Black Walnut (Fagales: Juglandaceae) in Washington State

Abstract The health and productivity of black walnut (Juglans nigra L.) is currently threatened by Thousand Cankers Disease (TCD), a pest complex comprised an insect vector, the twig beetle (WTB) (Pityophthorus juglandis Blackman) (Coleoptera: Curculionidae), associated pathogenic fungi (Geosmithia morbida Kolařík, Freeland, Utley, Tisserat) (Hypocreales: Bionectriaceae). There urgent need for tools to manage TCD avoid catastrophic losses in high-value plantations walnut. In this case study, we evaluated efficacy IPM strategies three TCD-infested Walla Walla, WA. At beginning our average weekly captures WTB per trap varied across sites; low (~32), moderate (~111), high (>1,300). Each site received separate management tactic: 1) girdled trees alone; 2) insecticide emamectin benzoate alone or combination with fungicide propiconazole protect healthy crop superior form; 3) chemically-protected trees. Walnut populations remained at consistently levels both after were deployed. where treated, crown condition those that matched exceeded treated untreated control Our findings suggest using integrated approach has most potential reduce valuable stands TCD.