Final report for SW22-939
Project Information
Washington State provides nearly all organic pome fruit grown in the USA with an estimated annual farm gate value of a half billion dollars. There are currently 31,000 certified organic acres of pome fruit in the state and it is expected to reach 38,000 by 2021. The dry climate of central WA during the growing season may not be always conducive to orchard diseases, but many pathogens can cause latent infections and result in decays once conditions become more favorable in storage. This limits the packers’ ability to store organic apples more than four months, after which losses to postharvest decays, topping 30%, become economically unsustainable. Beside sanitation, there are no effective organic control strategies currently. Producers suffer from a lack of knowledge about the efficacy of the few existing bio-fungicides, lack of more effective organic materials and knowledge about appropriate sprays and timing. Once organic apples are harvested, packers are limited to room, bin, and flume water sanitation to mitigate postharvest diseases, but often these strategies become ineffective after two months. Therefore, we propose to 1) evaluate organic materials (biological agents, plant extracts, GRAS) and develop a timely spay program, 2) collaborate with producers to test effective materials at commercial orchards in three main production regions to ensure efficacy under various conditions, and 3) evaluate the efficacy of dynamic controlled atmosphere to store organic fruit and curb decay. Economic analyses will evaluate the impact of the proposed management tactics on producers. Outreach activities will include field and warehouse days at producer sites, talks at state and regional commodity meetings, and the production of educational materials. This project will render the production and storage of organic tree fruit more sustainable to meet the increasing demand for safer produces and strengthen the competitiveness and the economy of the western region.
OBJECTIVE 1: Evaluate the efficacy of existing and new organic materials and develop a timely preharvest spray program (Research). 1) Evaluate the efficacy of organic materials applied preharvest against major pathogens causing postharvest diseases and on detached fruit, 2) develop a timely preharvest spray program to optimize management of postharvest decays.
OBJECTIVE 2: Evaluate enhanced management tactics in commercial orchards located in different productions regions of central Washington (Research). 1) Evaluate the efficacy of selected spray programs, at three commercial orchards in collaboration with our three collaborator producers, to control storage decays over short and extended storage periods. 2) Assess the economic impact (benefits/costs) of suggested new spray programs.
OBJECTIVE 3: Assess the efficacy of dynamic controlled atmosphere (DCA) to control or reduce infections of major postharvest pathogens (Research). 1) Evaluate the efficacy of DCA against four major postharvest pathogens on inoculated fruit in controlled and commercial conditions. 2) Assess the economic impact (benefits/costs) of DCA.
OBJECTIVE 4: Conduct a vigorous education and outreach program with input from our producer cooperators. Create and disseminate extension materials to growers and packers in the PNW and me measure improve in knowledge acquired by stakeholders and change in practices regarding organic disease management.
Cooperators
- - Producer
- - Producer (Researcher)
- - Technical Advisor (Researcher)
- - Producer
Research
Objective 1. Evaluate the adequacy and efficacy of current and novel preharvest management organic strategies (Year 1-2). Activity 1.1. Efficacy of existing and potential new products in the orchard: In a first step, we aimed to evaluate the efficacy of several treatments i.e. biocontrol agents, plant/microbial extracts, and bio-fungicides applied at a single time during the growing season against the most predominant pathogen in the PNW (Amiri and Ali, 2016). Trials were conducted on Gala apple at Sunrise experimental orchard in Wenatchee, WA, for two successive seasons. Treatments were applied with a backpack sprayer at appropriate timing and rates indicated on the label in a randomized complete block design (RCB) with four replicate trees for each treatment. Fruit were picked (25 fruit/replicate tree for a total of 100 fruit/treatment) at commercial maturity and stored in separate crates at 34°F and 90% HR in a RA. Disease incidence and identification of pathogens was carried out after 2, 4, and 6 months of storage or extended beyond as needed. Activity 1.2 and 1.3: Efficacy on detached fruit and Develop effective spray programs based on optimal timing and number of applications of combined treatments: To collect data on baseline efficacy of new materials they were tested on detached fruit inoculated with major pathogens. Based on preliminary data and the efficacy from activity 1, the best treatments at bloom and preharvest were combined for up to 5 applications from bloom to harvest. Extensive (up to 5 sprays/season) and conservative (1-2 sprays/season) spray programs were designed and tested for two successive seasons as described in Activity 1.
Objective 2. Evaluate enhanced management tactics in three commercial orchards located in different productions regions of central Washington. Trials were conducted in Years 2 & 3 at three commercial orchards in collaboration with our three cooperators: The first orchard is located in Tonasket (Godwin) north WA, the second (Stemilt) in central WA, and the third orchard (BZBlackrock) is located in south WA. The rationale is to test proposed management program on a larger commercial level and in different environmental conditions to ensure final recommendation would fit the needs of all stakeholders. At each site, a one-acre organic block of Gala or Honeycrisp (high value cultivars that suffer high disease incidence) were divided by 2 subblocks. One sub-block was sprayed following the grower spray calendar (one seven day preharvest spray) and the second sub-block was sprayed using our proposed program of 3 to 4 sprays throughout the season i.e. at petal fall, fruitlet, green fruit and 7 days preharvest. Each sub-block was divided into 4 sub-block replicates with equal number of trees. At commercial maturity fruit from each sub-block was harvested separately by the cooperators in collaboration with PI-Amiri and his team. Fruit were stored in a controlled atmosphere using the same conditions of commercial warehouses. After 6 months of storage, fruit were packed in each commercial packinghouse and decayed fruit were collected to determine incidence and decay type.
Objective 3. Evaluate the benefits of using dynamic control atmosphere (DCA), GRAS products and biocontrol agents to control rots in storage. (Year 1-2). While many benefits of DCA systems on the fruit quality and reduction of physiological disorders have been evidenced, the impact on disease reduction in such storage conditions is still unknown. The ability of fungi to survive in hypoxia varies but their metabolism is tremendously diminished. The DCA systems (O2 <1 to 0.3%) will only be relevant to pome fruit packers if a significant reduction in decay rate compared to static controlled atmosphere (1.5 to 3% oxygen) is shown. In Year 1 and 2, we focused on 3 key postharvest pathogens, i.e., Botrytis cinerea, Neofabraea perennans, and Penicillium expansum. For the two first pathogens, Fuji apples were inoculated with spore suspensions at 500,000 spores/ml on the trees 15 days prior to harvest to mimic pre-harvest conditions. For P. expansum , fruit picked at commercial maturity, will be surface-disinfected in sodium hypochlorite, rinsed with sterile water, and inoculated with spore suspensions of the pathogen at 500,000 spores/ml. Fruit inoculated were stored accordingly. Four replicates of 25 fruit each (total of 100 fruit/treatment) previously randomized using an RCB design were used. Decay incidence and severity were determined after 2, 4 and 6 months of storage. Additionally, 40 non-inoculated fruit (4 replicates of 10 fruit each), picked at commercial maturity, were stored in the same atmospheres for the same storage periods and were used to assess fruit quality parameters (firmness, solid content, sugar content, acidity). Fruit were stored in Safepod containers for the CA and DCA treatments.
Objective 1. Evaluate the adequacy and efficacy of current and novel preharvest management organic strategies (Year 1-2).
Activity 1.1. Efficacy of existing and potential new products in the orchard [2022-23 and 2023-24]
During the 2022-23 season, 16 organic materials were applied 7 days preharvest in a Fuji apple block in Rock Island, WA. One hundred fruit were harvested at commercial maturity (25 fruit x 4 replicate trees/treatment), stored at 35°F, and disease incidence was determined after 8 months. Overall disease incidence was 23.8% in the untreated control and 1.3% in the fruit treated with the conventional fungicide Thiophanate-methyl (used for Comparison). Among the organic materials, the most effective ones were Etidot-67, Blossom Protect and AVIV with 0% incidence, followed by Trilogy, Kaligreen, Sil-Matrix and Kocide 3000 with 1.3% equal to the efficacy of the conventional fungicide. Disease incidence ranged between 2.5 and 22.5% in the remaining organic materials tested. The trial was conducted again in the 2023-24 and 2024-25 seasons under similar field and storage conditions. After three consecutive trial seasons, the tested biofungicides were grouped into three groups based on their efficacy levels: Group 1 included four materials, Kaligreen, Actinovate, Cueva, Cinnerate, Group 2 included AVIV, Blossom Protect, and Sil Matrix, whereas Group 3 included six other materials. Groups 1, 2, and 3 reduced overall decay incidence by 6, 4.5 and 2 folds, respectively, compared to the untreated control.
Activity 1.2: Efficacy of select organic material against major postharvest pathogens on detached fruit [2022-23 and 2023-24]
Field trials (Activities 1.1 and 1.3) are important to assess the efficacy of organic materials. However, they many not provide specific efficacy against a given pathogen. Herein, we evaluated the efficacy of 12 organic materials against Penicillium expansum, Botrytis cinerea, Noefabaraea perennans, and Alternaria alternata, four major postharvest pathogens of pome fruit. Fruit at commercial maturity (2 replicates of 20 fruit each/treatment) were wounded at the equatorial zone and dipped for 1 min in the solution of each material at the label rate. Fruit were inoculated with 20 µl of spore suspension of each pathogen at 105 spores/ml and stored at 35°F for 8 months. In 2023, Botector, Jet-Ag, Actinovate and Double Nickel were the most effective against P. expansum (blue mold), with incidence <3% compared to 15% in the control. For B. cinerea (gray mold), Sil-Matrix, OSO, Serenade Opri, Jet -AG and Double Nickel reduced incidence the most <1% compared to 10% in the control. For N. perenanns (bull's eye rot), Sil-Matrix, Jet-Ag, AVIV, and OSO, reduced bull's eye rot incidence to 1% from 19% in the control. For A. alternata (Alternaria rot), incidence in the control was 6% and all organic materials but Actinovate and AVIV reduced incidence to <1%. During the 2024 season (using similar field and storage conditions), Cueava, Jet-Ag and Double Nickel were the most effective against P. expansum with incidence ranging between 10 and 23% compared to 58% in the untreated control. For the other pathogens, a trend similar to the one seen in the previous season was observed.
Activity 1.3: Develop effective spray programs based on optimal timing and number of applications of combined treatments [2023-24 and 2024-25]
In the 2023-24 season, 18 treatments were applied a solo materials or alternated throughout the growing season at an organic Fuji apple block in Rock Island, WA. Beside the untreated control, 4 organic materials were applied once in a season 7 days preharvest, 4 other treatments included 3 organic materials applied at 3 different phenological stages, 4 treatments consisting of 4 organic materials applied at 4 different phenological stages, four other treatments consisting of 5, 6, 7, and 8 organic treatment each applied at different phenological stages though the growing season in the orchard. Treatments were applied following the experimental design and approach described in Activity 1.1. At commercial maturity in October 2023 and 2024, 25 apples were harvested from each replicate tree (total of 100 fruit per treatment) and stored at 35°F for 8 months in regular atmosphere. In both seasons, spraying at four phenological stages [petal fall, fruitlet (1-1.5 inch), green fruit (2-4 inch) and 7 days preharvest] was consistently the most effective spray program with reductions up to 80% in disease incidence compared to the control. Treatments that did not include a petal fall spray and 7-days preharvest were the least effective. Selecting the most effective material 7-days preharvest only was effective in 2023 but in in 2024. While the program that includes 4 sprays in a season was found to provide the highest efficacy, spraying at petal fall and 7 days preharvest are highly recommended.
Objective 2. Evaluate enhanced management tactics in three commercial orchards located in different productions regions of central Washington [2023-24 and 2024-25]
Based on the efficacy of the organic material tested in Activity 1.1 (2022-23 season), 8 most effective materials were selected and applied them in rotation programs at two organic commercial orchards (Cooperators: Robinson and Badissy) in 2023-24 and in organic commercial orchard (Honeycrisp ) in 2024-25. The Robinson orchard is located in the Columbia Basin area (central WA) whereas the Badissy orchard was located in southeastern growing region. There were two programs in each orchard, one was the grower standard spray program (GSSP) and the other one was the research suggested spray program (RSSP). Each program was applied to 2 acres following the standard procedures followed by the growers. At commercial maturity, 800 fruit were harvest from each block (spray program) and stored at 35°F for 6 to 8 months. During the 2023-24 season, the overall disease incidence was 10.2% in the GSSP program versus 2.5% in the RSSP program at Robinson orchard and 29.3 and 6.8%, respectively, at the Badissy orchard. In the 2024-25 season, the disease incidence was 23% and 8% in the blocks sprayed using the GSSP and RSSP programs, respectively.
Objective 3. Evaluate the benefits of using dynamic control atmosphere (DCA), GRAS products and biocontrol agents to control rots in storage [2023-24 and 2024-25].
There was a failure in the controlled atmosphere system in 2022, therefore, results were not considered and the trial was conducted in 2023 and 2024. In the 2023-24 season, Fuji apples harvested at commercial maturity were inoculated with spore suspensions of P. expansum (blue mold), B. cinerea (Gray mold), or N. perennans (Bulls's eye rot), the three major postharvest pathogens of pome fruit. Fruit (100/pathogen) were incubated at 35°F in regular atmosphere (RA), static controlled atmosphere (CA), or dynamic controlled atmosphere (DCA). In 2023-24, an atmopshere of 1 to 1.5% oxygen and 0.5% CO2 was used as a DCA whereas a constant 4.0% O2 and 0.5% CO2 was used for regular CA. Blue mold incidence was 60, 65, and 55% in RA, CA, and DCA. For gray, the incidence was 3, 9, and 2, respectively, versus 80, 58, and 85%, respectively, for bull's eye rot (BER).
In 2024-25 season, the concentration of O2 was kept between 0.7 and 1% and that of CO2 was 0.7% in the DCA program, whereas the CA was kept the same as in 2023-24. Overall, disease incidence was higher in the DCA atmosphere compared to the CA and RA storage atmospheres for all the three tested pathogens with BER being the least sensitive to lower O2 concentrations. While additional research testing different atmospheres on different cultivars, our results indicate that very low oxygen concentrations <1%) may exacerbate decay in storage.
Research outcomes
Objective 1. Evaluate the adequacy and efficacy of current and novel preharvest management organic strategies (Year 1-2)
Activity 1.1. Efficacy of existing and potential new products in the orchard: Assessing the efficacy of 16 organic materials in the filed provided baseline data on their efficacy to reduce postharvest decays. Although trials are ongoing to confirm the results, we should be able at the end of this project to recommend at least 6 organic materials with a good level of efficacy for field sprays in organic orchards.
Activity 1.2: Efficacy of organic material on detached fruit. Early results, awaiting confirmation (Year 2), suggest that organic material tested have different efficacy level against major postharvest pathogens which may indicate that their rotation throughout the growing season would optimize decay control in storage.
Activity 1.3. Develop effective spray programs based on optimal timing and number of applications of combined treatments: Results from year 1 are expected int the summer of 2024.
Objective 2. Evaluate enhanced management tactics in three commercial orchards located in different productions regions of central Washington. Results from year 1 are expected int he summer of 2024.
Objective 3. Evaluate the benefits of using dynamic control atmosphere (DCA), GRAS products and biocontrol agents to control rots in storage. (Year 1-2). Results from year 1 are expected int he summer of 2024.
Education and Outreach
Participation summary:
Activity 4.1. Summarizing and Presenting data at stakeholder meetings:
Oral Presentations: Between 2023 and 2025, 16 talks about organic disease management were provided by the PI and his team at different meetings, including at national, regional, and local level. The PI was invited to speak about the topic at 8 different grower meetings. The PI provided two talks on DCA and efficacy of organic materials at two international conferences.
Field days: Two 1/2 field days were conducted during this project. One was organized in 2024 at the Badissy farm and was attended by 52 stakeholders. The second field day was in 2025 in the Robinson farm and was attended by 45 stakeholders. During these days, a summary of the results from the project were shared and handouts outlining science-based recommendations about managing diseases in organic apples were provided. The hosting growers shared their experiences and challenges were discussed.
Activity 4.2. Create and disseminate extension materials
Two extension publications on the topic have been published in the WSU Tree Fruit website the research was highlighted in the magazine Good Fruit Grower. From the work conducted in this project, 6 abstract and two conference proceedings were published. Work is ongoing to summarize the data and publish 3 peer-reviewed manuscripts.
Activity 4.1. Summarizing and Presenting data at stakeholder meetings:
Oral Presentations: PD Amiri and his Postdoctoral Assistant have provided 16 talks at different national and regional meetings attended in total by 658 people from the industry and scientific communities:
1-Amiri A. Managing decays in organic pome fruit. Annual Meeting of the Washington Fruit Association, Kennewick, December 6th 2023 (Attendees: 200).
2-Amiri A. Efficacy of organic materials applied preharvest to control fruit rots in storage. Columbia Basin Tree Fruit Club, Kennewick, July 26th 2023 (Attendees: 25).
3-Amiri A. Effective use of organic materials: preharvest for postharvest diseases. Wilbur Ellis Organic Grower Meeting, Benton City. Feb. 15th 2023 (Attendees: 68).
4-Fomba J. and Amiri. A. 2023. Effectiveness of organic materials applied in the orchards to control postharvest diseases of pome fruits. Plant Health Conference, Denver CO, August 2023. (Attendees: 200)
5-Amiri A., Fomba J. Update in the efficacy of organic materials in controlling postharvest decays of apples. WA Tree Fruit Association Annual meeting. Dec 6th 2022. (Attendees: 70).
6- Amiri A. Efficacy of current commercial preharvest organic materials. Workshop Pre and Postharvest Management in Organic Systems, Wenatchee, WA, March 9th 2022. (Attendees: 95).
Publications:
Season-long sprays support organic storage success. Researchers offer best practices for ensuring long-term health when storing organic apples. Good fruit Grower. February 2024.
Decay management a season-long effort. Good fruit Grower. March 2023
Education and Outreach Outcomes
1-Importance of field sanitation to reduce inoculum size in organic pome fruit orchards and warehouses. The impact and incidence of many pathogens causing rots on fruit during storage can be reduced by implementing sanitation practices pre and postharvest. Though outreach and education, we bring awareness to the importance of cultural/sanitation practices in fighting decays evven when other approach are used.
2-Importance of seasonal preharvest spray programs. Using epidemiological knowledge about major pome fruit pathogens is key to conduct targeted sprays using most effective materials to optimize decay reduction in storage. A single preharvest application, one week before harvest, is not the best recommendation.
3-Construct a bridge between pre and postharvest systems. Postharvest diseases of pome fruit in central Washington have been viewed as a storage issue because the symptoms are seen during storage. However, education and outreach efforts in the past a few years have been oriented towards increasing the awareness of the growers that the problem starts in the orchards and therefore, good communication and collaboration with postharvest decision makers is key to tackle the problem in increase their return.
- Preharvest disease management
- Efficacy of organic materials available in pome fruit
398: is the number of farmers who attended the talks provided by PD Amiri and his team in 2022 and 2023. Although surveys were not conducted, we estimate that a large majority of attendees have gained new knowledge attitude and awareness with managing postharvest diseases of pome fruit.