EPIDEMIOLOGY AND MANAGEMENT OF PRE- AND POSTHARVEST DISEASES OF SUB-TROPICAL AND TEMPERATE FRUIT AND NUT CROPS IN CALIFORNIA

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1016026
• Project Start Date: Jun 4, 2018
• Project End Date: Sep 30, 2022
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF CALIFORNIA, RIVERSIDE
(N/A)
RIVERSIDE,CA 92521

Performing Department
Plant Pathology, Riverside

Non Technical Summary
Sub-tropical and temperate fruit and nut crop commodities in California are constantly faced with challenges from fungal and bacterial plant diseases, as well as quarantine and regulatory restrictions. Invasive species and new disease outbreaks from endemic or introduced pathogens are ongoing issues that commodities need to address to allow uninterrupted production, marketing, and trade. Cultural practices also change with new cultivars, production regions, horticultural techniques, irrigation methods, and pest control materials including fungicides, bactericides, insecticides, and other pesticides. As climate and micro-climates within a crop production system change from year to year, plant pathogens and other organisms respond to these changes. All of these factors influence the challenges that growers face to produce a profitable crop and meet market demands. Understanding disease etiology and studying the biology, pathology, and epidemiology of fungal and bacterial diseases affecting California fruit and nut crops is an ongoing process and is essential in developing sustainable management strategies. Thus, this project continues to directly serve growers, packers, and pest control advisors of the sub-tropical and temperate fruit and nut crop industries of California and the United States and indirectly the consumers of these commodities. For fruit crops, a focus of our research has been the simultaneous development of novel pre- and postharvest treatments, as well as improved methods of using these treatments effectively through pathogen detection, environmental monitoring, predictive models, and new application technology. New treatments against fungal and bacterial diseases are being continuously developed in our program to ensure that treatments for effective disease control are available to combat disease outbreaks, development of resistance in pathogen populations, and changing regulatory requirements. For this, we are closely working with the world-wide agrochemical industries, commodity groups, growers, government programs, as well as regulatory agencies. Studies on fungicide and bactericide resistance have been an emphasis in our project. With all the new pesticide introductions, there are still relatively few chemical classes available and it is imperative to prevent their loss in efficacy or to justify their need to regulatory agencies. Through my program agricultural representative throughout the state are well aware of the risk of resistance development and support our recommendations of resistance management strategies. We are also continuously evaluating new biopesticides, natural products, and biocontrol agents. These products are generally less effective as compared to synthetic products, but still we have been identifying treatments that give adequate control under low-disease conditions. Additionally, some of the newly introduced biopesticides, biologicals, and natural products may be made available for the organic industry. A fungicide and bactericide summary document is on the UC-IPM website and includes information on the relative efficacy of treatments against several major diseases on each fruit crop, best use strategies that aim to optimize performance and minimizing the risk for resistance development, information on honey bee health, resistance management, and regulatory aspects.For the diagnosis and identification of fungal pathogens, cultural and molecular approaches will be used. Studies on the biology and host-pathogen interactions of fungal and bacterial pathogens will include inoculation studies as well as histological, qPCR, and other molecular approaches. In epidemiological studies, the effects of micro-environmental parameters such as temperature, precipitation, leaf wetness, and relative humidity on disease development will be evaluated in laboratory, growth chamber, and field experiments. Environmental conditions will be related to pathogen growth, primary and secondary infection periods, development of quiescent infections, disease progression, and epidemics. Mathematical models will be developed to describe and forecast epidemics for pathogens in specific crops. Environmental monitoring for resistance in non-target bacterial organisms will also be done to support bactericide registrations. Management programs will be developed to optimize an integrated approach of cultural practices, disease forecasting, natural host resistance, and fungicide or bactericide programs. Baseline sensitivities to newly introduced fungicides and bactericides will be developed, and pathogen populations will be monitored for their sensitivities when treatment failures after pesticide applications are reported. Fungicide and bactericide resistance mechanisms in pathogens will be characterized on a molecular basis.

Animal Health Component

90%

Research Effort Categories

Basic

10%

Applied

90%

Developmental

0%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
212	1199	1102	100%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants;

Subject Of Investigation
1199 - Deciduous and small fruits, general/other;

Field Of Science
1102 - Mycology;

Keywords

fungal and bacterial biology and identification

epidemiology

disease management

chemical control

Goals / Objectives
The primary objectives of this research are to determine the etiology of new disease outbreaks and study the epidemiology of fungal and bacterial diseases affecting California fruit and nut crops, including stone fruits (sweet cherry, peach, nectarine, plums), almonds, citrus, avocados, pome fruits (apples and pears), walnuts, olives, pomegranates, and strawberries. An improved understanding of the biology and epidemiology of fungal and bacterial pathogens will be used to develop management programs for controlling the diseases. This approach will help to guarantee minimal impact of pre-and postharvest diseases on crop loss and maintain trade of high-quality California agricultural commodities to domestic and international markets. Specifically, the objectives are as follows:Disease identification and biology of diseasesEpidemiology, modeling, and forecasting of diseases.Pre-harvest disease managementNatural host resistance in stone fruit and almond.Protective blossom and preharvest fungicide treatments and studies on fungicide resistance in the field.Protective bactericide treatments for management of bacterial diseases.Postharvest disease managementPostharvest sanitation to meet FSMA standards against food-borne human diseases and to reduce pathogen inoculum levelsPostharvest fungicide treatments and pathogen resistance against postharvest fungicides.

Project Methods
The fruit orchards required for experimentation are located on the UC Riverside (citrus, olive) and UC Davis Campuses (stone fruit, pome fruit, almond, olive, pomegranate, walnut), and at UC KARE in Parlier, CA (stone fruit, pome fruit, almond, pomegranate, walnut, kiwifruit). The Departments of Plant Pathology and UC KARE have the facilities for research on this program (cold rooms, postharvest treaters for fruits and vegetables, air-blast sprayers, and laboratory equipment).1A. Etiology - Disease identification.Identification of unknown causal agents of diseases will be done in a combined effort using pathogen isolation and Koch's postulates, as well as microscopy and molecular methods. For PCR, published primers will be used if available, or new primers will be designed from sequence analyses of selected genomic regions and comparison with closely related species. TaqMan qPCR procedures will be developed for pathogens where quantification is required or for pathogens to be directly detected in diseased plant tissue. Molecular detection and quantification of Phytophthora species of citrus will continue to be used. Similarly, we will also use TaqMan qPCR procedures for identification of Phytophthora pathogens of other crops such as almond and avocado. Genetic variability in bacterial pathogen populations will be evaluated using Rep-PCR; and for fungi, AFLP analyses, micro-satellite loci, or multi-locus sequence analyses will be used. RFLP analyses of amplified sequences previously were useful to us in the grouping of some pathogens like Penicillium species from pome fruits or Aspergillus species from prune, and these methods will be used again if appropriate diversity can be detected in a pathogen population.1B. Etiology - Biology of diseases.For studying infection processes of fungal pathogens we are using histological, scanning electron, and confocal microscopy.The nature and role of blossom and fruit infections as well as quiescent infections caused by the stone fruit brown rot pathogens will be investigated on almond and peach to determine when infections develop on susceptible and less susceptible genotypes. In citrus, we will microscopically evaluate initial germination and penetration stages of zoospores on orange fruit. For olive knot caused by Pseudomonas savastanoi pv. savastanoi, we will study the effects of wound healing of host tissue. In walnut research we will continue to evaluate microscopic features of fruit among walnut genotypes and compare to their susceptibility to blight caused by Xanthomonas arboricola pv. juglandis.2. Epidemiology, modeling, and forecasting of diseases.The effect of environmental factors (temperature, leaf wetness, relative humidity, precipitation) on infection and disease development will be evaluated in growth chamber studies under defined conditions and in the field under natural conditions. Environmental data will be recorded using digital data loggers. Disease progress data will be mathematically analyzed and models will be constructed. These models will be tested in the field and improved in subsequent years for the best fit. Disease progress curves and disease-environment interactions for specific host-pathogen combinations and environmental parameters such as precipitation, dew point, and temperature will be modeled. Research is currently ongoing for Alternaria and rust diseases, and Septoria spot and Phytophthora brown rot of citrus. For citrus brown rot, we are also evaluating temperature and wetness duration effects on zoospores infecting orange fruit.3. Preharvest disease management A. Natural host resistance.A large collection of peach germplasm will be evaluated from the breeding program at UC Davis. Susceptibility to blossom blight will be evaluated in inoculations of flowers in the field and on detached flowers in the laboratory, as well as based on natural incidence of disease. The basis of susceptibility will be related to pre-formed (constitutive) or adaptive responses resulting in physical or chemical barriers that limit the infection. Additionally, we will continue to evaluate walnut blight susceptibility among genotypes in the field and laboratory. Successful inoculation methods will be made available to the walnut breeding program at UC Davis. For almond we will continue to evaluate new genotypes and cultivars for their susceptibility to diseases that develop naturally in the field over the season including blossom blight, shot hole, scab, and rust. For this, a new almond variety block orchard was established at UC Davis in 2015 with newer genotypes.B. Protective blossom and preharvest fungicide treatments and studies on fungicide resistance in the field. Preharvest fungal diseases that will be evaluated include anthracnose, brown rot blossom blight and fruit rot, shot hole, gray mold, hull rot, Alternaria leaf spot, and scab of almond and stone fruit crops; Septoria spot, Phytophthora brown rot and root rot of citrus, and anthracnose and gray mold of strawberry. Treatments will be applied in experimental and commercial orchards following commercial practices using air-blast sprayers or other equipment. Treatments will be applied based on host phenology and environmental conditions, and one to five applications will be done depending on the disease involved. Experiments will be done using standard statistical methods and results for treatment efficacy will be obtained based on disease incidence and severity data.?C. Protective bactericide treatments for management of bacterial diseases.As part of an ongoing process, we are also continuing our evaluations of new field treatments against bacterial diseases. These include walnut blight, fire blight of pome fruits, olive knot, bacterial spot of almond, bacterial blast and canker of stone fruits, and angular leaf spot of strawberry. Experimental design and treatment application will be as described above for fungal diseases. Similar as for fungal pathogens, we will isolate and evaluate strains of bacterial pathogens for their sensitivity to registered and new bactericides.4. Postharvest disease managementA. Postharvest sanitation to meet FSMA standards for food-borne human diseases and to reduce plant pathogen inoculum levels. New sanitation and fungicide treatments will be studied in laboratory as well as experimental and commercial packingline experiments. Our collaboration with service companies will ensure that all tests will simulate commercial practices. In laboratory studies we will evaluate the in vitro toxicity of chemicals against selected postharvest fungal and surrogates of human bacterial pathogens. Sanitation materials planned for evaluation include acidified hydrogen dioxide, organic acids, and possibly other compounds approved by regulatory agencies in the United States (e.g., EPA, FDA, etc.). Efficacy for surface disinfestation of fruit crops and sanitation of fungicide solutions will be compared to that of sodium hypochlorite.B. Postharvest fungicide treatments and pathogen resistance against postharvest fungicides. New postharvest treatments with fungicides will be tested against decays of stone fruits (caused by Monilinia fructicola, Botrytis cinerea, Rhizopus stolonifer, and Geotrichum candidum), pome fruits (caused by Penicillium expansum, B. cinerea, Alternaria alternata, Mucor and Neofabraea species), citrus (caused by Penicillium spp., G. citri-aurantii and Phytophthora species), and gray mold of pomegranate. Fruit will be inoculated with the pathogens either before or after treatment to assess the post- and pre-infection activities of the materials, respectively, or naturally infected fruit will be used. Treatments will be applied as aqueous solutions or in diluted commercial fruit coatings using low- or high-volume sprays, dip or drench applications. A focus will be on the evaluation of natamycin and other newly available single and pre-mixture treatments.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Growers, commodity, and agricultural industry representatives, as well as regulators and policy makers concerning pesticides used for fungal and bacterial plant disease management. Information will be available to all races and creeds of people. Changes/Problems:Ongoing disease problems with isolated outbreaks include the following: A. Olive knot; B. Walnut blight; C. Fire blight of pome fruit with antibiotic field resistance to oxytetracycline for the first time; D. Brown rot and gray mold of stone fruits; E. Powdery mildew of cherry; F. Scab and Alternaria leaf spot of almonds; G. Hull rot of almonds; H. Phytophthora diseases of citrus, cherry, and almond; I. Septoria spot of citrus; J. Postharvest decays; and K. Anthracnose, angular leaf spot, and gray mold of strawberry. What opportunities for training and professional development has the project provided?Numerous commodity board, grower and professional presentations including disciplinary (American Phytopathological Society), as well as regulatory national forums between IR-4 and EPA. Commodities include almond, apple, avocado, cherry, citrus, kiwifruit, olive, peach, pear, pomegranates, prune, strawberries, and walnuts. Presentations made through UC ANR. How have the results been disseminated to communities of interest?Through publications, including articles, book chapters and scientific journals, as well as professional presentations (in-person, and on-line). What do you plan to do during the next reporting period to accomplish the goals?This project continues to directly serve growers, packers, and pest control advisors of the tree fruit and nut industries of California and the United States and indirectly the consumers of these commodities. Based on studying the etiology, epidemiology, biology, and management of fungal and bacterial diseases that are of importance in current crop production systems, we develop the most effective, economical, and environmentally safe management practices. We are developing new pre- and postharvest treatments as well as improved usage strategies through pathogen detection, environmental monitoring, predictive models, and new application technology.

Impacts
What was accomplished under these goals? For this project period, we continued research on foliar and soil fungicide treatments against Phytophthora brown rot and root rot of citrus caused by several Phytophthora spp. including P. citrophthora and P. syringae. Three new Oomycota-specific fungicides, fluopicolide (FPX), mandipropamid (MDP), and oxathiapiprolin (OXA), all with different modes of action, were registered nearly simultaneously on citrus. OXA and FPX were registered for soil applications, whereas OXA and MDP were registered for foliar use (Pub #5). Bioassays and HPLC-MS-MS analyses of plant extracts demonstrated the acropetal mobility of OXA and MEF into stems and leaves of potted plants when applied as soil treatments (Pub #3). Research on potassium phosphite confirmed resistance in populations of P. citrophthora, P. parasitica, and P. syringae. As a postharvest treatment, phosphite was only effective in reducing brown rot decay of citrus fruit caused by strains with high resistance (>150 ppm) when used at high rates (i.e., 8,000 ppm) in combination with heat (>50C) (Pub #6). On pear, P. lacustris was identified for the first time in California causing a fruit rot of Bartlett pear in commercial fields using river water in orchard sprinkler irrigation systems (Pub #2). Almond diseases were also studied. Bacterial spot was described for the first time as a new disease of almond in California (Pub #1). Genetic evaluations indicated homogenous populations of the pathogen collected from multiple locations and high sensitivity to copper and mancozeb. Both compounds have been registered on almond for decades. Dormant or delayed dormant treatments in combination with full bloom and petal fall applications of copper and mancozeb were highly effective in managing the disease. The pathogen overwinters in fruit mummies and spurs. The disease is favored by wetness and warm temperatures. Resistance in Alternaria alternata to five SDHI fungicides was characterized based on genetic mutations in the SDH-B and -C sub-units of the target gene (Pub #4).

Publications

• Type: Journal Articles Status: Published Year Published: 2020 Citation: Haack, S. E., Wade, L., F�rster, H. and Adaskaveg, J. E. 2020. Epidemiology and management of bacterial spot of almond caused by Xanthomonas arboricola pv. pruni, a new disease in California. Plant Dis. 104:1685-1693.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Hao, W., F�rster, H., Elkins, R. B., and Adaskaveg, J. E. 2020. First report of Phytophthora lacustris causing a fruit rot of Bartlett pear in California. Plant Dis. 104:2528.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Gray, M. A., Nguyen, K.A., Hao, W., Belisle, R. J., F�rster, H., and Adaskaveg, J. E. 2020. Mobility of oxathiapiprolin and mefenoxam in citrus seedlings after root application and implications for managing Phytophthora root rot. Plant Dis. 104:3159-3165
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Adaskaveg, J. E., Hao, W., F�rster, H., and Belisle R. 2020. A new era for managing Phytophthora diseases of citrus. Citrograph 11:62-67.
• Type: Book Chapters Status: Published Year Published: 2020 Citation: Adaskaveg, J. E., Luo, Y., and F�rster, H. 2020. Characterization of resistance to five SDHI sub-groups in Alternaria species causing leaf spot of almond in California. Pages 173-180, in: Modern Fungicides and Antifungal Compounds. Vol. IX. H. B. Deising, B. Fraaije, A. Mehl, E. C. Oerke, H. Sierotzki, and G. Stammler, eds., Deutsche Phytomedizinische Gesellschaft, Braunschweig, Germany
• Type: Journal Articles Status: Awaiting Publication Year Published: 2021 Citation: Hao, W., F�rster, H., and Adaskaveg, J. E. 2021. Resistance to potassium phosphite in Phytophthora species causing citrus brown rot and integrated practices for management of resistant isolates. Plant Dis.

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Growers and agricultural industry representatives. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Numerous commodity board, grower and professional presentations including disciplinary, as well as regulatory national forums between IR-4 and EPA. Ph.D. students have been involved in these projects. How have the results been disseminated to communities of interest?Through publications, including articles, book chapters and scientific journals as well as numerous extension presentations to agro-industry. What do you plan to do during the next reporting period to accomplish the goals?This project continues to directly serve growers, packers, and pest control advisors of the tree fruit and nut industries of California and the United States and indirectly the consumers of these commodities. Based on studying the etiology, epidemiology, biology, and management of fungal and bacterial diseases that are of importance in current crop production systems, we develop the most effective, economical, and environmentally safe management practices. We are developing new pre- and postharvest treatments as well as improved usage strategies through pathogen detection, environmental monitoring, predictive models, and new application technology.

Impacts
What was accomplished under these goals? For this project period, we conducted research on preharvest fungicide soil treatments against Phytophthora root rot of avocado caused by Phytophthora cinnamomi. In laboratory and greenhouse studies with different avocado rootstocks, four new Oomycota-specific and the two registered fungicides, all with different modes of action, were evaluated. Baseline sensitivity ranges for 71 isolates of P. cinnamomi from avocado in California and mean EC50 values to inhibit mycelial growth by ethaboxam, fluopicolide, mandipropamid, and oxathiapiprolin were established and compared to mefenoxam and potassium phosphite. In greenhouse soil inoculation trials with avocado rootstocks, mefenoxam and potassium phosphite were effective, however, oxathiapiprolin, fluopicolide, ethaboxam, and mandipropamid were more effective. Oxathiapiprolin reduced PRR incidence and pathogen population size in the soil by >90%, and plant shoot growth and root dry weight were significantly increased compared with the control and was one of the best treatments overall. We also continued our epidemiological and management studies on Septoria spot of citrus caused by Septoria citri that is a quarantine pathogen in Korea. An epidemiological model based on total precipitation and number of hours <-1C allows for forecasting the disease and timely application of fungicides. Five new highly efficacious fungicides have been identified that reduce copper usage and ensure that no fruit with fruiting structures of S. citri arrive in Korea. A qPCR-based system is used to properly diagnose the disease and to certify fruit for export in the NAVEK program. In postharvest research, we continued to develop the biopesticide natamycin as a new post-harvest fungicide to manage sour rot, green and blue molds, and other citrus decays. To improve its performance and overcome its lack of sporulation control, natamycin is best used in mixtures with propiconazole for effective sour rot management and in mixtures with other fungicides for Penicillium decay control on citrus. A key advantage of natamycin is that it is less likely to select for resistant isolates of targeted pathogens.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Belisle, R. J., Hao, W., McKee, B., Arpaia, M. L., Manosalva, P. and Adaskaveg, J. E. 2019. New Oomycota fungicides with activity against Phytophthora cinnamomi and their potential use for managing avocado root rot in California. Plant Dis. 103:2024-2032.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Adaskaveg, J. E., and F�rster, H. 2018. Update on Disease Forecasting and management of Septoria spot of citrus. Citrograph Fall 2018, 76-80.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Adaskaveg, J. E., F�rster, H., and Chen, D. 2019. Positioning natamycin as a post-harvest fungicide for citrus. Citrograph Fall 2019, 62-65.

Progress 06/04/18 to 09/30/18

Outputs
Target Audience:Growers, cooperative extension, commodity, and agricultural chemical and biological industry representatives, as well as state and federal regulators and policy makers concerning pesticides used for fungal and bacterial plant disease management. Information will be available to all races and creeds of people. Changes/Problems:Ongoing disease problems with isolated outbreaks include the following: A. Olive knot; B. Walnut blight; C. Fire blight of pome fruit with antibiotic field resistance to oxytetracycline for the first time; D. Brown rot and gray mold of stone fruits; E. Powdery mildew of cherry; F. Scab and Alternaria leaf spot of almonds; G. Hull rot of almonds; H. Phytophthora diseases of citrus, cherry, and almond; I. Septoria spot of citrus; J. Postharvest decays; and K. Anthracnose, angular leaf spot, and gray mold of strawberry. What opportunities for training and professional development has the project provided?Numerous commodity board, grower, and professional presentations including disciplinary, as well as regulatory national forums between IR-4 and EPA. ? How have the results been disseminated to communities of interest?Through publications, including popular articles, book chapters, and scientific journals, as well as cooperative extension meetings held on different commodities throughout the state. What do you plan to do during the next reporting period to accomplish the goals?This project continues to directly serve growers, packers, and pest control advisors of the tree fruit and nut industries of California and the United States and indirectly the consumers of these commodities. Based on studying the etiology, epidemiology, biology, and management of fungal and bacterial diseases that are of importance in current crop production systems, we develop the most effective, economical, and environmentally safe management practices. We are developing new pre- and postharvest treatments as well as improved usage strategies through pathogen detection, environmental monitoring, predictive models, and new application technology.

Impacts
What was accomplished under these goals? To continue to support the tree fruit and nut commodities of California, we conducted research on the biology, epidemiology, and management of bacterial and fungal diseases that are limiting production, international trade, and the overall economic success of growers. In our 2018 research, we demonstrated that P. citrophthora and P. syringae are found in very distinct niches in citrus grove soil or leaf litter, respectively (Pub #6). For managing diseases caused by Phytophthora species, we identified and characterized new fungicides for managing brown rot and root rot of citrus and avocado in California (Pub. #1, #3, and #7). This was significant because it established fungicide sensitivity baselines for four fungicides and demonstrated high activity of these fungicides in inhibiting multiple growth stages of Phytophthora species including P. syringae, a quarantine pathogen causing international trade restrictions of California citrus. Based on our research, oxathiapiprolin was registered for preharvest foliar and soil use on citrus in California. This fungicide is extraordinary with the lowest EC50 value of any fungicide we ever evaluated while having excellent human and environmental safety characteristics. With registration of the other identified fungicides, integrated resistance management programs can be developed. The new biofungicide natamycin was evaluated and registered as a preplant treatment of strawberry to protect against Colletotrichum acutatum isolates that are resistant to QoI fungicides (Pub #4). Viable resistance has not been reported in filamentous fungi with this fungicide and its registration is important in preventing selection and spread of resistance to other fungicides that are critical to strawberry production in California. In contrast to previously evaluated fungicides, natamycin has been characterized as having zero resistance potential in our assays. This is a major finding for breaking the resistance selection process to strawberry pathogens. We have also studied pre- and postharvest treatments to manage angular leaf spot of strawberry to overcome trade barriers for California strawberries (Pub #5). Evaluation of new bactericides and new fumigants such as propylene oxide that can eradicate the pathogen from plant tissues without causing phytotoxicity are essential to the future of the industry. In preharvest research on fungal pathogens, we evaluated microsatellites for improving our understanding of the pathogen Venturia carpophila occurring on almond, peach, and pecan (Pub #2). In our research on olive knot, we characterized the genetic diversity of Pseudomonas savastanoi pv. savastanoi and epidemiological factors in the development of olive knot California (Pub #9). In this publication, we identified treatment the critical treatment time after injury to obtain high efficacy. With the detection of copper resistance in the olive knot pathogen, new bactericides were evaluated for managing olive knot and registration of kasugamycin and oxytetracycline are pending (Pub #8). New bactericide registrations (each with different modes of action) for the management of olive knot will have a great impact in expanding olive production in California.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: 1. Belisle, R., McKee, B., Hao, W., Crowley, M. Arpaia, M.L., Miles, T. Adaskaveg, J. E., and Manosalva, P. 2019. Phenotypic characterization of genetically distinct Phytophthora cinnamomi isolates from avocado. Phytopathology ⿿ accepted 8/2/2018. 52 pages (Refereed, Electronic)
• Type: Journal Articles Status: Published Year Published: 2018 Citation: 2. Chen, C., Bock, C. H., Brannen, P. M., & Adaskaveg, J. E. (2018). Mining and characterization of microsatellites from a genome of Venturia carpophila. Mycological Progress, 17(8), 885⿿895. (Refereed, Electronic) https://doi.org/10.1007/s11557-018-1401-x
• Type: Journal Articles Status: Published Year Published: 2018 Citation: 3. Gray, M. A., Hao, W., Förster, H., & Adaskaveg, J. E. (2018). Baseline Sensitivities of New Fungicides and Their Toxicity to Selected Life Stages of Phytophthora Species from Citrus in California. Plant Disease, 102(4), 734⿿742. doi:10.1094/pdis-08-17-1155-re (Refereed, Electronic) https://doi.org/10.1094/PDIS-08-17-1155-RE
• Type: Journal Articles Status: Published Year Published: 2018 Citation: 9. Nguyen, K. A., Förster, H., & Adaskaveg, J. E. (2018). Genetic Diversity of Pseudomonas savastanoi pv. savastanoi in California and Characterization of Epidemiological Factors for Olive Knot Development. Plant Disease, 102(9), 1718⿿1724. doi:10.1094/pdis-11-17-1709-re (Refereed, Electronic) https://doi.org/10.1094/PDIS-11-17-1709-RE
• Type: Journal Articles Status: Published Year Published: 2018 Citation: 4. Haack, S. E., Ivors, K. L., Holmes, G. J., Förster, H., & Adaskaveg, J. E. (2018). Natamycin, a New Biofungicide for Managing Crown Rot of Strawberry Caused by QoI-Resistant Colletotrichum acutatum. Plant Disease, 102(9), 1687⿿1695. doi:10.1094/pdis-12-17-2033-re (Refereed, Electronic) https://doi.org/10.1094/PDIS-12-17-2033-RE
• Type: Journal Articles Status: Awaiting Publication Year Published: 2019 Citation: 5. Haack, S. E., Walse, S. S., Nguyen, K. and Adaskaveg. J. E. 2018. Management of Xanthomonas fragariae with pre- and postharvest treatments to overcome trade barriers for California strawberries. Plant Dis. 38 msp. Accepted on August 27, 2018. (Refereed, Electronic)
• Type: Journal Articles Status: Published Year Published: 2018 Citation: 6. Hao, W., Miles, T. D., Martin, F. N., Browne, G. T., Förster, H., & Adaskaveg, J. E. (2018). Temporal Occurrence and Niche Preferences of Phytophthora spp. Causing Brown Rot of Citrus in the Central Valley of California. Phytopathology, 108(3), 384⿿391. doi:10.1094/phyto-09-17-0315-r (Refereed, Electronic) https://doi.org/10.1094/PHYTO-09-17-0315-R
• Type: Journal Articles Status: Awaiting Publication Year Published: 2019 Citation: 7. Hao, W., Gray, M. A., Förster, H., and Adaskaveg, J. E. 2018. Evaluation of new Oomycota fungicides for management of Phytophthora root rot of citrus in California. Plant Dis., Accepted 9/14/2018, 42 pages (Refereed, Electronic)
• Type: Journal Articles Status: Published Year Published: 2018 Citation: 8. Nguyen, K. A., Förster, H., & Adaskaveg, J. E. (2018). Efficacy of Copper and New Bactericides for Managing Olive Knot in California. Plant Disease, 102(5), 892⿿898. doi:10.1094/pdis-08-17-1162-re (Refereed, Electronic) https://doi.org/10.1094/PDIS-08-17-1162-RE