Concurrent Session 2A
Thousand cankers disease and the walnut twig beetle: A rapidly emerging invasive threat to walnut in California (2011-2014)
Richard Bostock, Professor, Dept. of Plant Pathology, UC Davis
Steven Seybold, Dept. of Entomology/Nematology, UC Davis.
Thousand cankers disease (TCD) caused by Geosmithia morbida, a fungal pathogen transmitted by the walnut twig beetle, Pityophthorus juglandis (WTB) is an emerging disease that is responsible for decline and death of ornamental eastern black walnut, Juglans nigra, in the western states and native stands of this species in the eastern USA. In California, TCD is contributing to the decline of native black walnuts, Juglans californica and J. hindsii, and affecting English walnut, J. regia, and rootstocks in walnut orchards throughout the state. There is great concern over the further spread of TCD throughout the native range of the eastern black walnut and uncertainty about the potential impact on Juglans species of agricultural and ecological importance in California and the western USA.
• identified TCD frequently in native and ornamental stands of J. californica and J. hindsii, in black walnut seed trees for rootstock production, and throughout commercial walnut orchards in both English scions and Paradox rootstocks
• developed effective detection tools for both the beetle and the fungus, which have been placed into practice at a national and international level
• developed bilingual outreach programs that engaged stakeholders