Thousand Cankers Disease and the Walnut Twig Beetle: A Rapidly Emerging Invasive Threat to Walnut in California
Richard Bostock Department of Plant Pathology, UC Davis
Steven Seybold USDA Forest Service, Pacific Southwest Research Station and Department of Entomology and Nematology, UC Davis
UC ANR Joint Strategic Initiatives Conference October 6, 2015 Thousand cankers disease (TCD) history
Project objectives
Research highlights and detection tools
Outreach, disease management and future directions
Photo by Stacy Hishinuma An epidemic in eastern black walnut, Juglans nigra, in western states
• Mortality of J. nigra was first observed in Utah & Oregon in the 1990’s
• Mortality first observed in Colorado in 2001
• Disease widespread in Colorado Springs & Boulder by 2004
• By 2008 nearly all J. nigra trees in the Colorado Springs area were dead
• More than 2000 dead J. nigra in Boulder – Denver area
• Walnut twig beetle and new fungal pathogen associated with disease by Colorado State University scientists.
Photos by Ned Tisserat & Whitney Cranshaw, Colorado State University Dying Juglans hindsii (northern CA black walnut) trees outside Davis, CA in 2008
Photos by Steve Seybold and Andy Graves English walnut, Juglans regia
Jim LaBonte – Oregon Dept Ag Pityophthorus juglandis
Photo by C. Debuse walnut twig beetle (WTB)
Photo by J. Hasey Walnut Twig Beetle Pityophthorus juglandis
An ambrosia beetle, Xyleborinus saxeseni WTB
♂ ♀ Photos by A.D. Graves, UC-Davis Elizabeth Fichtner, UCCE Tulare County J. regia cv. Chandler Tulare County
Elizabeth Fichtner, UCCE Tulare County WTB makes galleries in the larger branches of the walnut tree
photo by Ned Tisserat & Whitney Cranshaw, Colorado State U.
Photo by Andy Graves, USDA FS Removal of outer bark tissue reveals galleries and canker Geosmithia morbida – a new species 2011
Sometimes find other canker fungi in disease samples also – can be tricky.
conidiophores and conidia
Infected bark pieces on agar
Sporulation on beetle and in galleries
Tisserat et al (2009) Plant Health Progress Kolarik et al (2011) Mycologia 103:325 Top view Bottom view Natural distribution of some native Juglans species in the USA
J. hindsii J. nigra J. californica
J. major
Zerillo et al. (2014) PLoS ONE 9(11):e112847 Comparative TCD Symptoms
Wolfskill NCGR Photo by Stacy Hishinuma Solano Co., CA
Juglans major Juglans californica (southern NM) (in northern CA)
Sporadic Numerous cankers, cankers, prolific staining on minimal staining bark surface on bark surface Distribution of TCD in the United States October, 2015
http://www.thousandcankers.com/quarantines.php WTB distribution in the USA December 2014
1960
1959
1896/1928
from Rugman-Jones et al. (2015) PLoS ONE 10(2):e0118264 WTB range expansion and spread of TCD?
native range of WTB
Zerillo et al. (2014) PLoS ONE 9(11):e112847 Rugman-Jones et al. (2015) PLoS ONE 10(2):e0118264 ANR project objectives
• Evaluate Juglans species for comparative disease reactions to Geosmithia morbida.
• Evaluate WTB host selection behavior.
• Assess disease and vector distribution in orchards and the diversity of California isolates of G. morbida.
• Extension and Outreach
• Develop improved isolation and detection methods for Geosmithia morbida. Juglans National Clonal Germplasm Collection USDA/ARS NCGR – Winters, CA
J. microcarpa J. ailantifolia J. mollis J. australis J. neotropica J. californica J. nigra J. cathayensis J. olanchana J. hindsii J. regia J. major J. sinensis J. mandshurica J. hindsii x J. regia (Paradox) Juglans National Clonal Germplasm Collection USDA/ARS NCGR – Winters, CA Eleven of fifteen species are developmental hosts for WTB
Developmental hosts of Pityophthorus juglandis J. microcarpa J. ailantifolia recorded from this J. mollis collection J. australis J. neotropica J. californica J. nigra J. cathayensis J. olanchana J. hindsii J. regia J. major J. sinensis J. mandshurica Transverse egg galleries of J. hindsii x J. regia P. juglandis etched onto (Paradox) the wood surface of a small branch of Arizona walnut, J. major. Juglans species show differences in susceptibility to Geosmithia morbida
A B BC BC CD CD CD D D D (P = 0.05) WTB Host Selection Behavior Unbaited live branch study
Juglans ailantifolia, J. californica, J. hindsii, J. major, J. microcarpa, J. regia (2012 and 2013)
Pterocarya stenoptera (2013)
1 uninfested branch/tree
From Stacy Hishinuma Landing rate of WTB on branches of six species of Juglans and one Pterocarya species
Juglans species effect : F 7,138 = 21.17; P<0.001 4 a (PROC GLIMMIX in SAS; Multiple means separation by Tukey-Kramer )
3.5
SE) ± 3
2.5
2 1.5 b 1 c c
0.5 c c c c No. WTB/branch/7 d (mean (mean d WTB/branch/7 No.
0
Juglans species from Stacy Hishinuma Beetle colonization
Photos by Steve Seybold & Stacy Hishinuma
The males colonize initially Joined by 1-2 females in the galleries
The males produce an aggregation pheromone that attracts the females. The more beetles there are in a colony, the more beetles are then attracted to the infested tree prenol Trapping WTB with pheromone lures Pheromone-baited sentinel branches harvested at 5 d and 12 d. Geosmithia morbida cultured from frass and phloem around new galleries
August, 2012
Stacy Hishinuma and Steve Seybold Five days after placement in the field: July 29, 2012 Seasonal variation in host susceptibility to G. morbida Peak periods of beetle flights (May-July & Sept-Oct) and host susceptibility may overlap in spring and summer
J. regia cv. Chandler
T. Nguyen, M. Yaghmour and S. Hishinuma, unpublished Chen & Seybold (2014) PLoS ONE 9(8): e105945 English scion
WTB appears to select Paradox over English
Paradox rootstock
Tulare County 2013 English WTB appears to select Paradox over English
P < 0.0001
Paradox
Armstrong Plant Pathology Research Station UC Davis Farm Advisor trainings and field surveys TCD Status in California English Walnuts
photos by Janine Hasey, UCCE
Confirmed TCD in rootstocks and English scions in: Butte, Contra Costa, Colusa, Fresno, Lake, San Joaquin, San Benito, Solano, Stanislaus, Sutter, Tehama, Tulare, Yolo, and Yuba counties TCD incidence and severity: Highest in southern San Joaquin Valley
Each pie chart represents disease incidence in that orchard (positive indicated in black) .
Farm advisor surveys: incidence from 0 to >90% trees with strikes.
M. Yaghmour, J. Hasey et al. unpublished Black walnut trees
= TCD positive
Detailed orchard surveys
G. morbida population genetics Mil Ulceras Enfermedad de Nogales Una Enfermedad nueva en California
Por Ricardo Hoenisch, Departamento de Fitopatología, UC Davis
34 Mil Ulceras de Nogales el género botánico Juglans El Malo
El Escarabajo El Bueno Foto de L.L. Strand.
El Feo
El Arbol El Hongo Why the current epidemic given long- association of WTB and G. morbida and presence of WTB for many decades?
36 Chuck Leslie, UCD Plant Sciences TCD management and future directions
• Fungicides? Insecticides? Unlikely
• Sanitation to mitigate spread – removal of dead and severely declining trees; grind or burn immediately. http://www.ipm.ucdavis.edu/EXOTIC/thousandcankers.html
• Do not transport/ship infested walnut material, especially where this is prohibited by state quarantines.
• Need to keep beetles from landing on trees: host selection behavior and chemistry of attraction/repulsion host and pathogen VOC’s as coattractants with pheromone
• Improved diagnostic tools Acknowledgements
UC Davis and UCCE USDA Tivonne Nguyen John Preece - ARS Tatiana Roubtsova Andy Graves - ARS Plant Pathology Mohammad Yaghmour Richard Hoenisch Stacy Hishinuma Entomology Colorado State University Mary Lou Flint Chuck Leslie Plant Sciences Ned Tisserat Elizabeth Fichtner Whitney Cranshaw Janine Hasey UCCE
Support from UC ANR, USDA ARS, USDA Forest Service, USDA APHIS, and USDA NIFA (NPDN)