UC Delivers

Thousand cankers disease research increases awareness and solutions for walnut industry

The Issue

Thousand cankers disease (TCD) is an emerging tree disease that is responsible for the death of ornamental eastern black walnut species throughout the country. In California, TCD is contributing to the decline of other native black walnut trees as well as English walnut trees in nut-producing orchards. TCD is caused by a fungal pathogen transmitted by the walnut twig beetle (WTB). There is great concern over the potential for further spread of TCD throughout the native range of eastern black walnut, as well as uncertainty about the disease’s potential agricultural and ecological impacts in the USA and in Italy, where it was first reported in 2013.

What Has ANR Done?

ANR established a three-year project to study TCD in California and to inform stakeholders about the latest research. A team from UC Davis, the USDA Forest Service, and UCCE has been working together to address critical gaps in our understanding of this new disease. The team has identified TCD frequently in native and ornamental stands of two species, in black walnut seed trees for rootstock production, and throughout commercial walnut orchards in both English and hybrid rootstocks. From this research the team has developed effective detection tools for both the beetle and the fungus, and these tools have been put into practice at both national and international levels.

The Payoff

New knowledge and solutions for the walnut industry

This research and the associated outreach programs have increased worldwide knowledge about disease biology and etiology for detection, generated interim solutions, raised awareness of TCD, and identified promising avenues for further study to limit the disease’s damage and spread. Growers who are particularly concerned about TCD are removing diseased trees and burning them to mitigate potential sources of the vector and inoculum in their orchards. Team members have actively engaged various stakeholders, including growers, regulatory biologists (CDFA and eastern state agencies), Master Gardeners, and scientists at state and national conferences. UCCE Advisors and the walnut industry in California have assimilated the new knowledge that this project has provided and are applying it in real-world conditions. Project members have received frequent invitations to present their latest information at scientific conferences and at UCCE- and industry-sponsored meetings.

Contact

Supporting Unit: Plant Pathology - CAES

Richard Bostock, Professor, 530-752-0308, rmbostock@ucdavis.edu
Steven Seybold, Research Entomologist, USDA Forest Service,530-759-1734, sjseybold@gmail.com