Walnut
132 - Chinese Mulberry Beetles
Principal Investigator: Dr. Hannah Nadel, Supervisory Entomologist, USDA-APHIS-PPQ, Buzzards Bay, Mass.
133 - Completion of Koch's Postulates for Putative Pistachio Pathogens
Principal Investigator: Dr. Elizabeth Fichtner, University of California Cooperative Extension Farm Advisor, Tulare County.
Over the past 5 years, several new diseases have emerged on California pistachios. Dr. Fichtner has been utilizing the new plant pathology laboratory and greenhouse space at Lindcove Research and Extension Center to conduct diagnostics on plant tissues submitted by growers and complete studies focused on the pathogenicity, epidemiology and management of new pistachio diseases.
In collaboration with Dr. Cheryl Blomquist, CDFA, and Dr. Greg Browne, USDA ARS, several new Phytophthora and Phytopythium species have been found associated with root rot and canker on pistachio. Fichtner’s current studies focus on completion of Koch’s Postulates for each new putative pathogen isolated from pistachio, as well as investigation of environmental conditions conducive to disease. Her research also addresses efficacy of phosphites and natural products for management of Oomycete pathogens on pistachio.
In 2014, Rhodococcus fascians, a gram positive, plant pathogenic bacterium, was determined to be the causal agent of pistachio bushy top syndrome, a new disease in California, Arizona, and New Mexico. Field symptoms of the disease include stunting, shortened internodes, swollen lateral buds, a light green color, and “bushy” growth resembling witches’ broom. Dr. Fichtner is collaborating with Dr. Jennifer Randall, New Mexico State University, and Craig Kallsen, UCCE Kern County, to determine the risk of soilborne inoculum to pistachio re-plants, as well as the risk of pathogen transmission on pruning tools. Another research emphasis is the screening of other plant materials, both crops and weeds, to identify putative sources of environmental inoculum.
125 - Duration of Walnut Twig Beetle Emergence from Infested Walnut Logs
Principal Investigator: Dr. Elizabeth Fichtner, University of California Cooperative Extension Farm Advisor, Tulare County
Walnut twig beetle (WTB), Pityophthorus juglandis, is the vector of thousand cankers disease (TCD), an emerging disease on walnut caused by the fungus Geosmithia morbida. TCD was originally reported in black walnut in Colorado, but the disease was confirmed in California (CA) in 2008 and has since been reported throughout the walnut-growing regions in CA. Since our first finding of TCD in Tulare Co. in 2009, both the documented incidences and the known geographic distribution of disease have increased gradually over time. The disease has been detected in commercial walnut orchards in Tulare, Fresno, and Kings Cos., and in the southern San Joaquin Valley (SJV), the pathogen has been isolated from Tulare, Chico, and Chandler varieties, as well as from both black and Paradox rootstocks. In an effort to better understand the seasonality of activity of the walnut twig beetle, we have been monitoring the WTB flights weekly at three trapping sites over a wide geographic area (Porterville, CA to Parlier, CA). Our recent results demonstrate minimal WTB activity from mid-November through early February, suggesting that removal of TCD-infected trees should be completed before February in the southern SJV as part of an orchard sanitation program. While growers may diligently remove infected trees from orchards, we often find WTB-infested wood present in firewood or burn piles adjacent to orchards. Consequently, the objective of this project is to address how long WTB emerge from infested wood removed from orchards, thus providing growers a temporal guideline for both tree removal and firewood use.