THOUSAND CANKERS DISEASE of WALNUT: STATUS in CALIFORNIA

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1 THOUSAND CANKERS DISEASE of WALNUT: STATUS in CALIFORNIA Janine Hasey UC Cooperative Extension, Sutter & Yuba cos. Steve Seybold USDA Forest Service, Davis

2 THOUSAND CANKERS Insect-vectored disease on walnut Walnut twig beetle carries fungal spores which infect phloem around entrance hole resulting in canker formation The fungus Geosmithia isolated from beetles, beetle galleries, and cankers Pending species name: G. morbida

3 ACKNOWLEDGEMENTS Geosmithia confirmations Ned Tisserat,, Colorado State University Suzanne Latham & Kathy Kosta,, CDFA Rick Bostock & Themis Michailides,, UCD

4 Walnut Twig Beetle (Pityophthorus juglandis) Jim LaBonte Oregon Dept Ag <1/10 long Etch galleries on xylem surface This is reportedly regarded as a minor pest associated with twig dieback (California)

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6 SYMPTOMS

7 CALIFORNIA STATUS Disease first found in Yolo Co. in June, 2008 & Solano Co. in July, 2008 Since then, confirmed in: Alameda, Los Angeles, San Joaquin, San Luis Obispo, Sutter, and Tulare Cos. Mostly in 2009 Likely been in CA for more than 5 years Walnut twig beetle First collected in 1959 in L.A. Co. Occurs in many counties from San Diego to Shasta Co.

8 WALNUT SPECIES USED IN AG Commercial Nut Production English walnut (Juglans( regia) 243,000 acres in CA in 2007 ~ 100% of U.S. production in CA Nursery Seed Trees Black walnut J. hindsii,, J. hindsii x J.nigra hybrid Rootstocks both from Black walnut sources Northern CA black Seedling Paradox hybrid (more vigor)

9 Near Rio Oso, Sutter Co., 88 yr Old Juglans nigra in a Backyard, April 14, 2009 Larval and adult P. juglandis were present beneath the bark of the main stem in mid-april; therefore larvae can overwinter in California. P. juglandis was trapped landing on the main stem of this tree into Oct The remainder of the crown collapsed in early July 2009.

10 Yuba City, Sutter Co., Commercial Orchard of ~20 yr Old J. hindsii x J. nigra interplanted by row with J. regia, July 27, 2009 Mainly infection and infestation in black walnut hybrids, not in English walnut. Photos: J.K. Hasey, UC Cooperative Extension, Sutter/Yuba Counties; S.J. Seybold, and L. Strand, UC Statewide IPM

11 INFECTED PARADOX ROOTSTOCK Geosmithia sp. was isolated from seedling Paradox rootstock in same orchard in Sutter Co.

12 SURVEY CROWN RATING Twig Dieback or Limited Crown Thinning 1- Healthy Tree 5 Dead Tree 3- Moderate Crown Thinning 4 Excessive Crown Thinning to Major Branches

13 Survey of Commercial Orchard for TCD, Sutter Co., California, Sept.-Oct., 2009 Species N Percentage Infected (mean ± S.E.) English walnut (J.( regia) on Paradox hybrid rootstock Geosmithia sp. was isolated from one specimen of English walnut, which was removed prior to the disease survey. Black walnut hybrid (J.( hindsii x nigra) ) on Paradox hybrid rootstock ± 2.9% Infection severity level based on composite survey data of crown rating, branch stain rating, stem stain rating, and presence/absence of WTB exit holes # of infected trees Low Medium High Level of Infection

14 Infected English Walnut Trees Tulare cultivar in Tulare Co. All English trees stressed with trunk cankers or root problems. Appears not to be Top-Howard cv. in Sutter Co a significant host to beetle Bottom-Howard cv. in Solano Co. (2 trees)

15 SUMMARY: WALNUT SPECIES Species J. nigra CONFIRMED in CA Urban X Riparian/ Native Ag J. hindsii X X X J. hindsii x J. nigra J. regia X X J. californica X X Paradox rootstock X X

16 OTHER CONSIDERATIONS Cultured black walnut seed from infected branches of J. hindsii x J. nigra No Geosmitihia found on hull or in nut Fusarium not found yet in CA Beetle may successfully colonize stressed trees There is the susceptibility issue of tree species to both the beetle and to the fungus.

17 Research/slide: Ned Tisserat

18 PRESENT & FUTURE PLANS Koch s s postulates in CA Testing insecticides and fungicides next spring on infected and non- infected walnut trees More extensive surveys of J. regia and rootstocks for the disease

19 Thank You Questions? Photo by Elizabeth Fichtner