Progress 09/01/23 to 08/31/24
Outputs
Target Audience:The primary target audiences for this project are organic growers of the following fruit crops peach, blueberry, mango, and avocado in the country, particularly in Florida, Georgia, South Carolina, California, and Hawaii, research and extension scientists, extension agents, students, and other stakeholders who are in business with low-chill stone fruit production. The results were communicated to growers, extension agents, researchers, and the public through different extension venues. 1) A hybrid outreach event titled "Hawaii Mango Research Projects Workshop" was held on September 23, 2023 and provided an educational opportunity to learn about mango production and current research in Hawaii, including the use of potassium nitrate to stimulate off-season mango production, and on-going evaluations on the effectiveness of Thyme Guard® for organic management of mango pathogens such as anthracnose (Colletotrichum spp.) and powdery mildew (Oidium mangiferae) (presented by L. Keith). Event participants were made aware of the project's funders and collaborative partners. There were 6 attendees. 2) From October 5-7, 2023, Jr. Extension Agent, Matt Miyahira participated in the Hawaii Tropical Fruit Growers' 33rd Annual HTFG Conference at the Blaisdell Center in Honolulu with an educational booth display. About 100 attendees were provided with information about the project, the Sept. presentations, and the Weebly mango webpage. He received questions about Thyme Guard®, mango diseases, and production and was able to communicate directly with producers who visited his booth. 3) Plant Derived Essential Oil Products: Safety and Efficacy for Organic Peach and Blueberry Disease Control. Southeast Regional Fruit and Vegetable Conference, January 11-13, 2024, GA. 4) Plant Derived Essential Oil Products for Disease Control in Blueberry. Blueberry Connections with the Industry, March 3, 2024, FL. 5) Use of Plant Essential Oil Products for Anthracnose and Other Diseases. Spring Harvest: Road Trip and Tour!" by Millstone Farm - May 18, 2024, FL. 6) In CA, the project goals were disseminated by direct conversations with avocado growers. The results were shared with the orchard owner, management, and farm advisors. 7) Efficacy of Thyme Guard®, Timorex ACT®, and Kocide®-2000-O for controlling fruit diseases in 'Valencia Pride' mango and 'Tower 2' avocado under South Florida grove conditions, June 2024, Florida State Horticulture Society, Orlando, Fl. 8) Results from Recent Organic Blueberry Disease Management Trials in Georgia, October 2024, Auburn, AL. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Five undergraduate research Assistants have been trained in field research, experimental design, diagnostics, and disease management under organic production. All assistants have been gaining independence in leading experiments in this project. In addition, they have been participating in all projects internal meetings with other PIs and have been actively communicatingand working with our collaborators from other states. They all have gained research-project management skills with this grant. Three master's students (located at the University of Florida, University of Georgia, and Clemson University) have recruited and increased their skills in plant disease diagnosis, disease management, fungicide research-based work, and organic production of fruit crops. A Ph.D. student (located at the University of Florida) has recruited and increased her skills in and postharvest physiology and postharvest pathology research-based work in fruit crops, and organic production of fruit crops. Two postdocs in the field of plant pathology have been recruited to conduct lab, greenhouse, and on-farm research-related works. One postdoc at the University of Florida main campus to manage related research works in peach and blueberry and the other postdoc at UF-Tropical Research and Education Center, in the south of Florida to manage research-related works in mango and avocado. Graduate students and postdocs trainees had the opportunity to increase professional development and communication skills through participation in local and international conferences. Postdocs have also gained useful skills in research-project management, student mentoring, and organic agriculture. A master's student and a postdoc trainee had increased their professional development and communication skills through participation in extension activities with growers and conference meetings with academic peers. Both have also gained knowledge of organic agriculture and production of tropical fruit crops. How have the results been disseminated to communities of interest?Results from the project have been disseminated to growers, as well as to the scientific and academic community. A list of events including organization and/or participation of the team members is presented below. NIFA support has been properly acknowledged in these events. 1) A hybrid outreach event titled "Hawaii Mango Research Projects Workshop" was held on September 23, 2023 and provided an educational opportunity to learn about mango production and current research in Hawaii, including the use of potassium nitrate to stimulate off-season mango production, and on-going evaluations on the effectiveness of Thyme Guard® for organic management of mango pathogens such as anthracnose (Colletotrichum spp.) and powdery mildew (Oidium mangiferae) (presented by L. Keith). Event participants were made aware of the project's funders and collaborative partners. There were 6 attendees. 2) From October 5-7, 2023, Jr. Extension Agent, Matt Miyahira participated in the Hawaii Tropical Fruit Growers' 33rd Annual HTFG Conference at the Blaisdell Center in Honolulu with an educational booth display. About 100 attendees were provided with information about the project, the Sept. presentations, and the Weebly mango webpage. He received questions about Thyme Guard®, mango diseases, and production and was able to communicate directly with producers who visited his booth. 3) Plant Derived Essential Oil Products: Safety and Efficacy for Organic Peach and Blueberry Disease Control. Southeast Regional Fruit and Vegetable Conference, January 11-13, 2024, GA. 4) Plant Derived Essential Oil Products for Disease Control in Blueberry. Blueberry Connections with the Industry, March 3, 2024, FL. 5) Use of Plant Essential Oil Products for Anthracnose and Other Diseases. Spring Harvest: Road Trip and Tour!" by Millstone Farm - May 18, 2024, FL. 6) In CA, the project goals were disseminated by direct conversations with avocado growers. The results were shared with the orchard owner, management, and farm advisors. 7) Efficacy of Thyme Guard®, Timorex ACT®, and Kocide®-2000-O for controlling fruit diseases in 'Valencia Pride' mango and 'Tower 2' avocado under South Florida grove conditions, June 2024, Florida State Horticulture Society, Orlando, Fl. 8) Results from Recent Organic Blueberry Disease Management Trials in Georgia, October 2024, Auburn, AL. What do you plan to do during the next reporting period to accomplish the goals?The results of this project will be published in peer-reviewed journals. We will focus on finish the data analyses, write, and submit the manuscript describing our results.Project results will be disseminated through participation in extension activities, growers' association meetings, scientific meetings, and through social media.Publish results of emerging mango postharvest fungal plant pathogens in Hawaii and share the information with growers, HDOA, and APHIS.Upkeep of the tropical fruit website, communications via our newsletters, and direct and indirect contact and outreach with producers and the industry will continue. A final hybrid outreach workshop is planned for Oct. 2, 2024 via Zoom and at the Kona Extension Office. Also, we are committed to participating with an educational booth display at the Hawaii Tropical Fruit Growers' 34th Annual HTFG Conference on Maui from October 4-6, 2024. Farm visits and communications with fruit producers will continue.
Impacts
What was accomplished under these goals?
Obj. 1 (in-vitro & detached leaf assays):The efficacy of Thyme Guard (TG) for target spot disease was evaluated in vivo using a detached stem assay. The 0.5% label rate of TG was applied to potted 'Colossus' blueberry plants grown inside a greenhouse. After 24h, stems with attached leaves of treated and non-treated plants were collected and then inoculated in the lab with a conidial suspension of Corynespora cassicola (105 spores/ml). Inoculated stems with attached leaves were sealed inside one of three replicate transparent plastic boxes with a moist paper towel lining the bottom. The boxes were placed in a dark incubator maintained at 25°C. Stems assigned to the post inoculation treatment were removed from the box 24h after inoculation and treated with 0.5% TG to runoff then returned to the sealed box where they were incubated. Disease incidence was recorded as a proportion of leaves with target spot symptoms on each detached stem. Disease severity in the percent leaf area affected was measured using APS Assess software (APS Press). Each treatment was applied to 3 to 5 detached stems per replicate. While uninoculated or water/mock-inoculated leaves remained free of symptoms, target spot symptoms were observed on leaves of all inoculated branches. A lower disease severity and slightly lower incidence was noted in our TG treated 24hr after inoculation treatment. Target spot control assessment results for SHB cultivar 'Colossus in vivo: Treatment and amount Application timingz Disease Severity (%)y Disease Incidencex Uninoculated control ---- - - Inoculated control ---- 79.6 a 1.0 a TGHiPre 1150 μl L-1 24 hrs before inoculation 74.6 a 1.0 a TGHiPost 1150 μl L-1 24 hrs after inoculation 8.4 b 0.74 b z Treatments were applied only once.y/x Recorded for 9-15 leaves per treatment.Means in each column followed by the same letter are not significantly different according to the least significant difference test (LSD)(α=0.05). Obj. 2 (on-farm trials): Blueberry: In 2024, on-farm trials were set-up to evaluate essential oils alongside other organic fungicides for control of fruit rot diseases (Anthracnose ripe rot, Botrytis fruit rot, and Alternaria fruit rot) and leaf spot diseases (Anthracnose leaf spot, blueberry leaf rust, and Septoria leaf spot) at two commercial organic blueberry production sites near Baxley, GA. Two trials were set-up, one on rabbiteye blueberry (Vaccinium virgatum) cultivar 'Brightwell' and one on southern highbush (SHB) blueberry (V. corymbosum interspecific hybrids) cultivar 'Farthing'. Fungicide treatments for both trials consisted of: OSO 5% SC, ThymeGuard, Kocide, and DART. For applications of OSO 5% SC, the OMRI-listed non-ionic surfactant Kinetic was added at 0.05% v/v. Five replications of each treatment and the untreated control were applied to a randomized complete block design. Anthracnose fruit rot incidence was very low in fruit collected from both SHB 'Farthing' and rabbiteye 'Brightwell' plants, with less than 0.5% of fruit affected by this rot on the untreated control plants of both cultivars. On SHB 'Farthing', other fruit rots, including Alternaria fruit rot were observed, but the overall incidence of fruit rot was very low (<5% in most cases). On rabbiteye 'Brightwell' fruit, an even lower incidence of fruit rots were observed, with less than 1% of the untreated control fruit affected by any type of rot . None of the tested treatments in either trial were determined to have significantly reduced Anthracnose fruit rot, Alternaria fruit rot, or all rots. The relatively higher incidence of fruit rot observed on the plants treated with ThymeGuard may be a consequence of the fruit damage (phytotoxicity) observed after applications of this treatment. Furthermore, it should be noted that the damaged fruit on the plants treated with ThymeGuard were relatively smaller than the fruit harvested from the plants receiving other treatments in this trial. Mnago: Data from the first two seasons were analyzed. There was no significant difference in average panicle rating prior to harvest and % disease incidence and severity were similar for both mango varieties (Rapoza and Manzanillo) regardless of treatment (Grower standard: Copper/Sulfur versus ThymeGuard®). After grower consultation, field efforts focused on diagnosis of emerging fungal pathogens. Avocado: No significant differences were found between the untreated control and ThymeGuard-treated trees in 2024. Overall, Thymeguard did not affect the vegetative or reproductive growth, responses to abiotic stressors, nor productivity of the trees.No significant differences were detected between the untreated control and thymeguard-treated trees regarding disease scores for avocado lace bugs and avocado branch canker caused by Botryosphaeriaceae species, nor for Anthracnose caused by Colletotricum spp and Alternaria alternata disease symptoms in Thymeguard-treated trees after the first spray compared with the control trees. Obj. 3 (postharvest): Essential oils offer a viable alternative to traditional postharvest fungicides because they are natural, safe for people and the environment, and have low resistance potential for pathogens. During postharvest treatment with Thyme oil (TO) fumigation and ThymeGuard (TG) immersion, strong antifungal activity was demonstrated in controlling peach brown rot. In spite of this, improper concentrations and treatment durations may result in phytotoxicity in the fruit. It was also observed that different cultivars of peach were sensitive to TO and TG treatments in different ways. In this study, detailed symptoms of TO phytotoxicity were found on peaches, and this is the first report demonstrating distinct symptoms as a result of fumigation and immersion treatments. Based on a combination of factors including EO concentration, treatment duration, storage length, fruit cultivar, and fungal strain, the efficacy of EO treatment can be varied. It is therefore imperative to pre-test the EO concentration range before applying postharvest treatments to specific fruit species and cultivars. Obj. 4 (outreach): Project results have been disseminated through direct interaction with peach, blueberry, avocado and mango growers in five states: FL, GA, SC, CA, and HI, and through participation in growers' associations and scientific society meetings already explained at "Target Audience Part". In HI, results were communicated with project farm collaborators and with the mango and avocado industries via phone, email, (11) farm visits, and bi-monthly newsletters. A website https://hawaiitropicalfruits.weebly.com houses information on the project and mango production in Hawaii. In CA, the project goals were disseminated by direct conversations with avocado growers. The results were shared with the orchard owner, management, and farm advisors. Organic Peach and Blueberry Disease Control results were disseminated in the Southeast Regional Fruit and Vegetable Conference, January 11-13, 2024, GA. Project results were also disseminated in other venues in the southeast, such as blueberry growers meeting I FL and Southeast Professional Fruit Works Conference in Alabama.
Publications
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2024
Citation:
Chang, Y., Boukari, W., Riley, S.S., Harmon, P.F., Sarkhosh, A., Brecht, J.K. (2024). In vitro antifungal activity of white thyme, oregano, and savory oils against five Monilinia fructicola isolates from the Southeastern United States. Plant Health Progrgress, 25, PHP-12.
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2024
Citation:
Ga��n-Betancur, L., Crane, J.H., Schaffer, B., Vargas, A.I., Sarkhosh, A., Gazis, R. (2024). Essential oils for managing anthracnose in mango (Mangifera indica): laboratory results do not translate into field efficacy. Plant Disease, 108, 3033-3043
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2024
Citation:
Chang, Y. (2024). Efficacy of Essential Oil for Managing Postharvest Quality and Reducing Decay of Peach Fruit. Ph.D. Dissertation, University of Florida.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Crane, J., Gazis, R., Ganan Betancur, L., Schaffer, B. (2024). Efficacy of Thyme Guard�, Timorex ACT�, and Kocide�-2000-O for controlling fruit diseases in Valencia Pride mango and Tower 2 avocado under South Florida grove conditions, June 2024, Florida State Horticulture Society, Orlando, Fl.
|
Progress 09/01/22 to 08/31/23
Outputs
Target Audience:The primary target audiences for this project are organic growers of the following fruit crops peach, blueberry, mango, and avocado in Florida, Georgia, South Carolina, California, and Hawaii, research and extension scientists, extension agents, students, and other stakeholders who are in business with low-chill stone fruit production. Our initial results were communicated to growers, extension agents, researchers, and the public through different extension venues. 1) Hybrid Workshop titled "Update on using organically certified essential oils for control of foliar and fruit diseases of avocado and mango" on UF, Tropical Research and Education Center, Homestead South FL. June 21, 2023. There were 18 in-person and 32 online participants (64 people registered for the meeting, 27 women, 37 men, 15 Latin-X, 10 Asian-X, and non-determined African Americans). Of the participants 50% were commercial producers representing ~124 acres, 20% represented educational institutions, 10% represented packinghouses, and 10% came from the landscape industry (10% others). 2) Oral presentation "Fruit Rot Management: Conventional and Organic Plant-based Essential Oil Products", Southeast Regional Fruit and Vegetable conference, Jan 5-8th, 3023, Savanna, GA. 3) Oral presentation "Standardizing diagnostic techniques and assessing fungicide sensitivity in Elsinoe perseae, an old foe of avocado production in south Florida", the 100th Southern Division meeting of the American Phytopathological Society, February 13th-16th, 2023, Durham, NC. 4) Oral Presentation "Challenges and insights into the use of essential oil based biopesticides for the management of foliar and fruit diseases in avocado and mango", the 18th biennial meeting of the Florida Phytopathological Society, May 17th-19th, 2023, Immokalee, FL. 5) Oral Presentation "Developing resources to facilitate the accurate identification of avocado scab (Elsinoe perseae)", the 18th biennial meeting of the Florida Phytopathological Society, May 17th-19th, 2023, Immokalee, FL. 6) Oral Presentation "Use of plant essential oil products for Anthracnose and other fruit rot disease management in blueberry", the 18th biennial meeting of the Florida Phytopathological Society, May 17th-19th, 2023, Immokalee, FL. 7) Oral presentation "Generating classical and molecular resources for accurate identification of avocado scab (Elsinoe perseae)", the 56th Annual Meeting of the Caribbean Food Crops Society, July 10th-14th, 2023, Grenada, PR. 8) Oral presentation "Spraying with uncertainty: Challenges and insights into the use of essential oil-based biopesticides for the management of foliar and fruit diseases in avocado and mango", the Annual conference of the American Society for Horticultural Science, July 1st-August 4th, 2023, Orlando, FL. 9) Oral presentation "From laboratory to consumer: Evaluating Anthracnose management in blueberry using plant essential oil products", the Annual conference of the American Society for Horticultural Science, July 1st-August 4th, 2023, Orlando, FL. 10) Oral presentation "Comparison of thyme oil vapor and Thyme Guard® immersion on peach postharvest brown rot control", the Annual conference of the American Society for Horticultural Science, July 1st-August 4th, 2023, Orlando, FL. 11) Oral presentation "Use of Plant Essential Oil Products for Anthracnose and other Fruit Rot Disease Management in Blueberry." the Annual Meeting of the American Phytopathological Society, August 12th-16th, Denver, CO. 12) Poster "In vitro antifungal effect of essential oil-based biopesticides and synthetic fungicides against the avocado scab pathogen Elsinoe perseae", the Annual Meeting of the American Phytopathological Society, August 12th-16th, Denver, CO. 13) Hybrid outreach event titled "Hawaii Mango Research Projects Workshop" September 22, 2022, HI. 14) Communications with project farm collaborators and with the mango and avocado industries via phone, email, (5) farm visits, and bi-monthly newsletters. A website https://hawaiitropicalfruits.weebly.com houses information on the project and mango production in Hawaii. 15) Communications with project farm collaborators and with the avocado farmers via phone, email, farm visits, in California. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Five undergraduate research Assistants have been trained in field research, experimental design, diagnostics, and disease management under organic production. All assistants have been gaining independence in leading experiments in this project. In addition, they have been participating in all projects internal meetings with other PIs and have been actively communicating and working with our collaborators from other states. They all have gained research-project management skills with this grant. Three master's students (located at the University of Florida, University of Georgia, and Clemson University) have recruited and increased their skills in plant disease diagnosis, disease management, fungicide research-based work, and organic production of fruit crops. A Ph.D. student (located at the University of Florida) has recruited and increased her skills in and postharvest physiology and postharvest pathology research-based work in fruit crops, and organic production of fruit crops. Two postdocs in the field of plant pathology have been recruited to conduct lab, greenhouse, and on-farm research-related works. One postdoc at the University of Florida main campus to manage related research works in peach and blueberry and the other postdoc at UF-Tropical Research and Education Center, in the south of Florida to manage research-related works in mango and avocado. Graduate students and postdocs trainees had the opportunity to increase professional development and communication skills through participation in local and international conferences. Postdocs have also gained useful skills in research-project management, student mentoring, and organic agriculture. A master's student and a postdoc trainee had increased their professional development and communication skills through participation in extension activities with growers and conference meetings with academic peers. Both have also gained knowledge of organic agriculture and production of tropical fruit crops. How have the results been disseminated to communities of interest?Results from the project have been disseminated to growers, as well as to the scientific and academic community. A list of events including organization and/or participation of the team members is presented below. NIFA support has been properly acknowledged in these events. 1) Hybrid Workshop titled "Update on using organically certified essential oils for control of foliar and fruit diseases of avocado and mango" on UF, Tropical Research and Education Center, Homestead South FL. June 21, 2023. There were 18 in-person and 32 online participants (64 people registered for the meeting, 27 women, 37 men, 15 Latin-X, 10 Asian-X, and non-determined African Americans). Of the participants 50% were commercial producers representing ~124 acres, 20% represented educational institutions, 10% represented packinghouses, and 10% came from the landscape industry (10% others). 2) Oral presentation "Fruit Rot Management: Conventional and Organic Plant-based Essential Oil Products", Southeast Regional Fruit and Vegetable conference, Jan 5-8th, 3023, Savanna, GA. 3) Oral presentation "Standardizing diagnostic techniques and assessing fungicide sensitivity in Elsinoe perseae, an old foe of avocado production in south Florida", the 100th Southern Division meeting of the American Phytopathological Society, February 13th-16th, 2023, Durham, NC. 4) Oral Presentation "Challenges and insights into the use of essential oil based biopesticides for the management of foliar and fruit diseases in avocado and mango", the 18th biennial meeting of the Florida Phytopathological Society, May 17th-19th, 2023, Immokalee, FL. 5) Oral Presentation "Developing resources to facilitate the accurate identification of avocado scab (Elsinoe perseae)", the 18th biennial meeting of the Florida Phytopathological Society, May 17th-19th, 2023, Immokalee, FL. 6) Oral Presentation "Use of plant essential oil products for Anthracnose and other fruit rot disease management in blueberry", the 18th biennial meeting of the Florida Phytopathological Society, May 17th-19th, 2023, Immokalee, FL. 7) Oral presentation "Generating classical and molecular resources for accurate identification of avocado scab (Elsinoe perseae)", the 56th Annual Meeting of the Caribbean Food Crops Society, July 10th-14th, 2023, Grenada, PR. 8) Oral presentation "Spraying with uncertainty: Challenges and insights into the use of essential oil-based biopesticides for the management of foliar and fruit diseases in avocado and mango", the Annual conference of the American Society for Horticultural Science, July 1st-August 4th, 2023, Orlando, FL. 9) Oral presentation "From laboratory to consumer: Evaluating Anthracnose management in blueberry using plant essential oil products", the Annual conference of the American Society for Horticultural Science, July 1st-August 4th, 2023, Orlando, FL. 10) Oral presentation "Comparison of thyme oil vapor and Thyme Guard® immersion on peach postharvest brown rot control", the Annual conference of the American Society for Horticultural Science, July 1st-August 4th, 2023, Orlando, FL. 11) Oral presentation "Use of Plant Essential Oil Products for Anthracnose and other Fruit Rot Disease Management in Blueberry." the Annual Meeting of the American Phytopathological Society, August 12th-16th, Denver, CO. 12) Poster "In vitro antifungal effect of essential oil-based biopesticides and synthetic fungicides against the avocado scab pathogen Elsinoe perseae", the Annual Meeting of the American Phytopathological Society, August 12th-16th, Denver, CO. 13) Hybrid outreach event titled "Hawaii Mango Research Projects Workshop" September 22, 2022, HI. 14) Communications with project farm collaborators and with the mango and avocado industries via phone, email, (5) farm visits, and bi-monthly newsletters. A website https://hawaiitropicalfruits.weebly.com houses information on the project and mango production in Hawaii. 15) Communications with project farm collaborators and with the avocado farmers via phone, email, farm visits, in California. What do you plan to do during the next reporting period to accomplish the goals?Data analysis from on-farm trial results will generate new knowledge on the mode of action and efficacy of EOs in controlling fungal pre- and postharvest diseases in peach, bluberry, avocado, and mango. Project results will be disseminated to communities of interest through participation in extension activities, growers' association meetings, scientific meetings, and through social media. The results of this project will be published in peer-reviewed journals. .
Impacts
What was accomplished under these goals?
Obj. 1(in-vitro & detached leaf assays):The efficacy of three plant essential oils (EO) thyme oil (TO) , oregano oil (OO), and savory oil (SO) and two commercial fungicides Thyme Guard (TG, thyme oil) and Timorex Act (TA, tea tree oil) were evaluated against a total of 10 fungal isolates from blueberry [6 Colletotrichum gloeosporioides (3 from Florida and 3 from Georgia), two Lasiodiplodia theobromae, one Corynespora cassiicola isolate, and one Neofusicoccum ribis (all from Florida)] as well as six Monilinia fructicola isolates from peach half of which originated from South Carolina and the other from Florida. TG followed by OO and SO showed efficacy against all fungal isolates from blueberry regardless of species or origin. The same inhibitory pattern was observed with Monilinia isolates growth where they were highly or completely inhibited by TG, TO, OO and SO. Although TG was effective in inhibiting our sole Corynespora isolate growth, none of the oil products tested showed efficacy against Lasiodiplodia and Neofusicoccum isolates. Similarly, TA shows very low efficacy against all tested isolates while at times it seems to enhance growth at some or all concentrations (hormesis) across species. Also, the in vitro antifungal activity of biofungicides TG, TA, and Cinnerate® (CI) was tested against six strains of Elsinoe perseae previously collected from avocado trees in Homestead, FL. A standard amended agar assay was used to determine the dose response effects of each EO on the growth rate of the pathogen. Biofungicides with thyme oil or cinnamon oil completely inhibited the mycelial growth of E. perseae, at active ingredient concentrations higher than or equal to 125 µl/l and showed fungicide activity at a minimum active ingredient concentration of 250 µl/l and 125 µl/l, respectively. There was no complete inhibition of the growth of E. perseae colonies at any of concentrations of TA. It is the first time that the in vitro fungicidal activity of biofungicides with thyme oil or cinnamon oil, as the active ingredient, against E. perseae was reported. Obj. 2 (on-farm trials): In 2023, on-farm blueberry trials were set-up to evaluate essential oils alongside other organic fungicides for control of fruit rot diseases (Anthracnose ripe rot, Botrytis fruit rot, and Alternaria fruit rot) and leaf spot diseases (Anthracnose leaf spot, blueberry leaf rust, and Septoria leaf spot) at two commercial organic blueberry production sites near Baxley, GA and an organic blueberry production site in FL. Using the following varieties Arcadia, Avanti, Farthing, Meadowlark, Brightwell, and Farthing. Fungicide treatments for consisted of: non treated control, OSO, TG, TA, and CI. A total of eight applications were made every 6-8 days depending on weather during the weeks preceding harvest. No treatment effect was observed for all evaluated diseases, but a varietal effect was detected. In 2023, on-farm peach trials control of brown rot with fungicide sprays was examined in FL on UFSun variety and SC on Juneprince variety. Fungicide treatments consisted of: OSO 5% 13 fl oz, OSO 5% 13 fl oz + 0.5% PureSpray Green, OSO 5% 13 fl oz+ 0.25% ThymeGuard, 0.5% ThymeGuard + 0.5% PureSpray Green, Cinnerate 64oz, and Cinnerate 64oz + 0.5% PureSpray Green. Brown rot incidence was relatively high in the untreated controls for preharvest (1DPreH; 24.5%) and high for 3 and 7 days postharvest (DPostH; 44.0% and 90.8%, respectively. Only OSO 5% and OSO 5%+ThymeGuard were statistically different from the untreated control at 1DPreH, however, they were not statistically different from all other treatments. Only OSO 5% was statistically different from the untreated control at 3DPostH. No treatments were statistically different from the untreated control at 7DPostH, however, OSO 5% +ThymeGuard had significantly less brown rot incidence compared to ThymeGuard+PureSpray Green. Treatments including PureSpray, including Cinnerate+PureSpray Green, ThymeGuard+PureSpray Green and OSO 5%+PureSpray Green, caused highest premature leaf drop. Cinnerate also exhibited significant premature leaf drop. A second-year on-farm trial was established on avocado and mango. Fungicide treatments for consisted of: untreated control, TG, TA, Kocide®-2000-O (KO) or TG+KO. Overall, no phytotoxicity symptoms on leaves, panicles-flowers, and/or fruit were observed after repeated applications of treatment. The two treatments that included KO had high efficacy for the control of powdery mildew, blossom blight, anthracnose, algal leaf spot, and scab, with disease incidence levels that were significantly lower than those observed in untreated control, TH and TA. The incidence of powdery mildew was slightly lower in TG and TA treated trees , but statistically the same when compared to untreated control. There were no differences in disease suppression when comparing the application of KO versus TG+KO. Obj. 3 (postharvest): Preharvest spray of blueberry and peaches with TG and grower standard practice did not reduce fruit postharvest decay incidence in blueberry and peaches. Thyme oil vapor fumigation at 24°C for 24 hours can significantly reduce brown rot lesion diameter after 6 days of storage at 1°C. Thyme oil vapor fumigation at 24°C for 24 hours can significantly reduce brown rot lesion diameter after 6 days of storage at 1°C. Dipping fruit in Thyme Guard solution for 30 seconds significantly reduces the brown rot lesion diameter after 7 days of storage in a 1°C cold room. The TO vapor effectively inhibited the growth of anthracnose, but also reduced fruit firmness and caused significant color change. The highest TO concentration (0.5 mL per 500 mL) completely eliminated decay development for at least 3 days at room temperature in inoculated and uninoculated groups. However, there were no significant differences (P>0.05) in the percentage of disease incidence among mango and avocado fruit treated preharvest with EOs and fruit harvested from trees of the non-treated control. Obj. 4 (outreach): Project results have been disseminated through direct interaction with peach, blueberry, avocado and mango growers in five states: FL, GA, SC, CA, and HI, and through participation in growers' associations and scientific society meetings already explained at "Target Audience Part". On June 21, 2023, a hybrid workshop titled "Update on using organically certified essential oils for control of foliar and fruit diseases of avocado and mango" was organized by the team and included the oral delivery of four presentations reporting activities and results obtained during the project development. Results were communicated with project farm collaborators and with the mango and avocado industries via phone, email, (5) farm visits, and bi-monthly newsletters. A website https://hawaiitropicalfruits.weebly.com houses information on the project and mango production in Hawaii. On August 13, 2022, Co-PI Kawabata and staff participated in the Mango Festival held in Kailua-Kona where approximately 1,500 attendees were exposed to this project and made aware of an upcoming hybrid event to share preliminary results of the project. A hybrid outreach event titled "Hawaii Mango Research Projects Workshop" was held on September 22, 2022 and provided an educational opportunity to learn about mango production and current research in Hawaii including the use of potassium nitrate to stimulate off-season mango production, and on-going evaluations on the effectiveness of Thyme Guard® for organic management of mango pathogens such as anthracnose (Colletotrichum spp.) and powdery mildew (Oidium mangiferae)). Event participants were made aware of the project's funders and collaborative partners.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2023
Citation:
Ga��n-Betancur, L. and Gazis, R. (2023). Genome Sequence Resource of the Avocado Scab Pathogen Elsinoe perseae. Microbiology Resource Announcement: e00190-23.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2024
Citation:
Chang, Y., Boukari, W., Riley, S.S., Harmon, P.F., Sarkhosh, A., Brecht, J.K. (2023). In vitro antifungal activity of white thyme, oregano, and savory oils against five Monilinia fructicola isolates from the southeastern US. Phytopathology Research, Submitted.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2023
Citation:
Belizaire, C. M. (2023). Characterization of the avocado scab pathogen Elsinoe perseae and its sensitivity to synthetic and natural fungicides. Masters degree Thesis, University of Florida.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Belizaire, C. M., Ga��n-Betancur, L, Sarkhosh, A., Harmon, P, and Gazis, R. (2023). In vitro antifungal effect of essential oil-based biopesticides and synthetic fungicides against the avocado scab pathogen Elsinoe perseae. (Abstr.) Phytopathology
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Boukari, W., Chang, Y., Belizaire, C.M., Sarkhosh, A., Brecht, J.K., Harmon, P. (2023). Evaluating Anthracnose management in blueberry using plant essential oil products. ASHS Annual Conference, Orlando, FL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Boukari, W., Chang, Y., Belizaire, C., Sarkhosh, A., Brecht, J.K., Harmon, P. (2023). Use of Plant Essential Oil Products for Anthracnose and other Fruit Rot Disease Management in Blueberry. (Abstr.) Phytopathology.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Chang, Y., Sarkhosh, A., Brecht, J.K. (2023). Comparison of Thyme Oil Vapor and Thyme Guard� Immersion on Peach Postharvest Brown Rot Control. ASHS Annual Conference, Orlando, FL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Belizaire, C. M., Ga��n-Betancur, L., Crane, J., and Gazis, R. (2023). Standardizing diagnostic techniques and assessing fungicide sensitivity in Elsinoe perseae, an old foe of avocado production in south Florida. (Abstr.) Phytopathology
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Belizaire, C. M., Ga��n-Betancur, L, Crane, J. H., and Gazis, R. (2023). Generating classical and molecular resources for accurate identification of avocado scab (Elsinoe perseae). In: Proceedings of the 56th Annual Meeting of the Caribbean Food Crops Society.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Ga��n-Betancur, L. Crane, J. H., Schaffer, B., Sarkhosh, A., Vargas, A. I., Melcon, R., and Gazis, R. (2023). Spraying with uncertainty: Challenges and insights into the use of essential oil-based biopesticides for the management of foliar and fruit diseases in avocado and mango. ASHS Annual Conference, Orlando, FL.
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Progress 09/01/21 to 08/31/22
Outputs
Target Audience:The primary target audiences for this project are organic growers of the following fruit crops peach, blueberry, mango, and avocado in Florida, Georgia, South Carolina, California, and Hawaii, research and extension scientists, extension agents, students, and other stakeholders who are in business with low-chill stone fruit production. Our initial results were communicated to growers, extension agents, researchers, and the public through different extension venues. 1) Preliminary results were presented to peach growers in Florida at the Peach Field Day - UF Citra on April 26, 2022 2) Shared project details and preliminary findings with UF's plant pathology faculty and students as a part of the Departmental Seminar Speaker series in spring 2022 - March 29, 2022 3) Presenting our finding on anthracnose of blueberry as a poster presentation at the Plant Health 2022 Conference on August 6-10 in Pittsburg, PA 4) Present "Evaluation of thyme oil vapor for control of postharvest anthracnose on blueberry" at the 2022 Florida State Horticultural Society Annual Conference on May 5th -7th. 5) Present "Achieving sustainable anthracnose management in organically grown avocado and mango orchards in south Florida"at the 2022 Florida State Horticultural Society Annual Conference on May 5th-7th. 6) Present the results in the NE1836 meeting on July 29th. 7) Present "Thyme oil vapor postharvest treatment for decay control can cause damage to peach and blueberry fruits" at the 2022 American Society for Horticultural Science Annual Conference on July 30th - August 3rd. Changes/Problems:Lack of cold days affected mango flowering, causing a low yield of mango fruits affected the evaluation of anthracnose suppression on fruits and postharvest storage. Due to the devastating late freeze event that occurred at the trial site on March 13th (see above), no blueberry fruit could be harvested for postharvest assays at the Georgia organic blueberry trial location. As such, these assays could not be performed during 2022, and we were unable to evaluate the impact of essential oils on blueberry postharvest fruit rot development. What opportunities for training and professional development has the project provided?Five undergraduate research Assistants have been trained in field research, experimental design, diagnostics, and disease management under organic production. All assistants have been gaining independence in leading experiments in this project. In addition, they have been participating in all project internal meetings with other PIs and have been actively communicating and working with our collaborators from other states. They all have gained research-project management skills with this grant. Three master's students (located at the University of Florida, University of Georgia, and Clemson University) have recruited and increased their skills in plant disease diagnosis, disease management, fungicide research-based work, and organic production of fruit crops. A Ph.D. student (located at the University of Florida) has recruited and increased her skills in and postharvest physiology and postharvest pathology research-based work in fruit crops, and organic production of fruit crops. Two postdocs in the field of plant pathology have been recruited to conduct lab, greenhouse, and on-farm research-related works. One postdoc at the University of Florida main campus to manage related research works in peach and blueberry and the other postdoc at UF-Tropical Research and Education Center, in the south of Florida to manage research-related works in mango and avocado. Graduate students and postdocs trainees had the opportunity to increase professional development and communication skills through participation in local and international conferences. Postdocs have also gained useful skills in research-project management, student mentoring, and organic agriculture How have the results been disseminated to communities of interest?Preliminary results were presented to growers in Florida during the 135th Annual Meeting of the Florida State Horticultural Society (FSHS) with the presentation titled "Achieving sustainable anthracnose management in organically grown avocado and mango orchards in south Florida". A scientific note was submitted and will be published in the proceedings of the FSHS meeting. CO-PI Gazis and postdoctoral researcher Gañán-Betancur are very active on social media (e.g., Twitter) and have been continuously posting short descriptions of the team's progress and outcomes to reach more end-users, including specialists, growers, and educators worldwide. NIFA support has been properly acknowledged as well through social media. Additionally, preliminary research results were disseminated internationally, in Spanish, to the scientific and academic community during the 1st meeting of the Colombian Association of Mycology with the talk titled "In vitro antifungal activity of plant-derived essential oils against anthracnose pathogens in the Colletotrichum gloeosporioides group". Preliminary results were presented to peach growers in Florida at the Peach Field Day - UF Citra on April 26, 2022. Shared project details and preliminary findings with UF's plant pathology faculty and students as a part of the Departmental Seminar Speaker series in spring 2022 - March 29, 2022. Presenting our finding on anthracnose of blueberry as a poster presentation at the Plant Health 2022 Conference on August 6-10 in Pittsburg, PA. Present "Evaluation of thyme oil vapor for control of postharvest anthracnose on blueberry" at the 2022 Florida State Horticultural Society Annual Conference on May 5th -7th. Present "Achieving sustainable anthracnose management in organically grown avocado and mango orchards in south Florida" at the 2022 Florida State Horticultural Society Annual Conference on May 5th -7th. Present the results in the NE1836 meeting on July 29th. Present "Thyme oil vapor postharvest treatment for decay control can cause damage to peach and blueberry fruits" at the 2022 American Society for Horticultural Science Annual Conference on July 30th - August 3rd. What do you plan to do during the next reporting period to accomplish the goals?The fungicidal activity of EOs against the avocado scab pathogen E. perseae will be tested through in vitro assays that are currently being implemented. A second round of detached-leaf assays will be carried out to corroborate results of the efficacy of EOs against anthracnose and peach rust. Glasshouse experiments, using container-grown blueberry, peach, avocado, and mango of the for detached leaf assays, will be conducted to test the suppression of anthracnose by EOs. Results from the first-year of the on-farm trial will inform which is the best timing for application and the frequency of sprays with EOs to optimize disease control during the second year of the on-farm trial. Altogether, data analysis from in vitro, detached leaf, and glasshouse assays will generate new knowledge on the mode of action and efficacy of EOs in controlling fungal diseases. Postharvest assays on avocado and mango will be carried out to determine the efficiency of EO applications on fruit shelf life and to determine how long treated fruit with EOs in the field remain disease-free on the shelf compared to non-treated fruit. Project results will be disseminated to communities of interest through participation in extension activities, growers' association meetings, scientific meetings, and through social media
Impacts
What was accomplished under these goals?
Obj. 1 (in-vitro & detached leaf assays): Various levels of antifungal activity were observed on thyme (TO), oregano oils (OO) and Thyme Guard (TG) amended plates. TO, followed by TG and OO respectively showed high to complete inhibition of all Collectotrichum isolates at low concentrations. Monilinia isolates growth was also highly or completely inhibited by TO, OO, and TG. The same trend was also observed for sole Corynespora isolate growth. In contrast, only low to no inhibitory activity was observed against Lasiodiplodia and Neofusicoccum isolates. The results showed that TO (both, as a commercial formulation and non-formulated extract) and savory oil (non-formulated extract) had consistent fungicidal activity against the ten C. spp. isolates tested, whereas a lesser fungicide activity was observed on media amended with Timorex Act (TA). The commercial formulation of thyme oil showed the highest fungicide activity (MFC= 250 µl/l; MIC= 125-250 µl/l; EC50= 48 µl/l), followed by the non-formulated extract of thyme oil (MFC= 1000 µl/l; MIC= 500-1000 µl/l; EC50= 167 µl/l) and the non-formulated extract savory oil (MFC= 1000 µl/l; MIC= 500-1000 µl/l; EC50= 203 µl/l). None of the TA concentrations tested achieved 100% or 50% mycelial growth inhibition. Likewise, no fungal growth was observed in any of the isolates during the second assay testing the commercial formulation of TO (250 µl/l), non-formulated TO (1000 µl/l), and non-formulated savory oil (1000 µl/l). Therefore the in vitro fungicide activity of thyme oil and savory oil on C. spp. was also confirmed. In blueberry detached leaf assay using Corynespora, no lesions were observed on control leaves after 14 days and only small ones were observed on day 16. In contrast, well-defined lesions were seen on all inoculated leaves. Visually, there were many more lesions on leaves that were first sprayed with TG then inoculated compared to their counterparts that were inoculated first and then sprayed with TG. There also seems to be numerical differences in percent lesion area between all treatments. In the avocado and avocado detached leaf assay using Collectotrichum, only the fungicide propiconazole significantly reduced (P < 0.05) the development of anthracnose lesions on mango leaves compared to the other treatments. The damage caused by anthracnose on mango leaves treated with essential oils (EOs) was severe and similar to the damage observed on leaves treated with water. Obj. 2 (on-farm trials): Leaf spot diseases, with a moderate incidence (61.3% and 46.7%) of blueberry leaf rust observed on the untreated control plots of 'Farthing' and 'Alapaha', respectively. A low incidence of other leaf spot diseases, including Septoria leaf spot and Anthracnose leaf spot, were also observed. On either cultivar, the essential oil treatments (TG and TA) did not significantly reduce blueberry leaf rust or all leaf spots relative to the untreated control in these trials. Among all treatments on SHB cv. 'Farthing', the lowest numerical incidence and severity of blueberry leaf rust was observed following applications with OSO 5% SC or PureSprayGreen, however no significant differences among treatments were noted in this trial. With respect to all leaf spots on cv. 'Farthing', the lowest severity and leaf area affected were also observed in the OSO 5% SC and PureSprayGreen treated plots, but these values were not significantly different from the untreated control. No phytotoxicity was observed at any time following treatment applications on blueberry plants. Disease incidence on blueberry fruits was evaluated every week after the second application while leaf disease incidence was evaluated a few weeks after harvest. On peach, leaf disease incidence was evaluated toward the end of the growing season and disease incidence on fruit was done at harvest, no treatment effect was observed on fruits. None of the treatments were significantly different from each other for preharvest brown rot control. For mango and avocado, disease evaluation of inflorescences (blossom blight) was conducted at full bloom, and disease evaluation on leaves and fruits (anthracnose) was conducted after the last spray, for the first-year data indicated no significant differences among mean values for blossom blight incidence and severity among trees treated with EOs and the non-treated control or the water-treated control. Likewise, no significant differences were observed in leaf anthracnose incidence and severity among trees treated with EOs and those in the non-treated control or water-treated treatment. Representative samples were collected and processed in the laboratory. C. spp. was confirmed as the causal agent of the symptoms observed in the on-farm trials. No TG phytotoxicity was observed in 'Hass' avocado leaves, flowers, or fruits at any rate tested for the whole time course of the experiment. TG had no impact on the retention of flowers and fruit setting. Obj. 3 (postharvest): Preharvest spray of blueberry and peaches with TG and grower standard practice did not reduce fruit decay incidence in blueberry. Also, different concentrations of TO did not show any effect on reducing fruit decay incidence in blueberries. The TO vapor effectively inhibited the growth of anthracnose, but also reduced fruit firmness and caused significant color change. The highest TO concentration (0.5 mL per 500 mL) completely eliminated decay development for at least 3 days at room temperature in inoculated and uninoculated groups. Thyme oil vapor may potentially provide a new and effective strategy for controlling postharvest anthracnose disease in blueberry fruit. Further research in sensory evaluation is needed to determine consumer acceptability due to the strong influence of TO on organoleptic properties. Peach cv. UFSharp was exposed to TO vapor at 0 mL, 0.5 mL, 1 mL, 2.5 mL, and 5 mL per 5000 mL plastic box with six fruits in each box and four replications of each treatment. All peach fruit were stored in a 1 °C and 95% relative humidity (RH) cold room for 7 days and then move to polypropylene fruit trays at room temperature (24 °C and 50% RH) for another 3 days. Fruit damages were displayed with different symptoms in the two fruit species. The TO vapor at ≥0.X mL reduced blueberry fruit firmness and caused significant color change. The negative effects of TO applications should always be carefully considered and evaluated. We observed that a higher rate can cause part of the peach epidermis to turn brown, becoming soft and easily peeled off by slight touching. Mango fruits were harvested and packed by growers. Individual boxes contained 4 to 6 fruits depending on variety and treatment. Fruits were assessed for ripeness and disease incidence and severity at days 0, 4, 7, 11 and 14 using a visual scale. Average ratings were calculated on the first date that the fruit became ripe or overripe. Post-harvest observations are still on-going. Overall, symptoms of anthracnose are present on all fruits regardless of the treatment. Once tests are complete, results will be statistically analyzed and reported in the next project report. Obj. 4 (outreach): Preliminary results were presented to peach growers at the Florida Peach Field Day. Shared project details and preliminary findings with UF's plant pathology faculty and students. Presenting our finding on anthracnose of blueberry at the Plant Health 2022 Conference. Preliminary results have been disseminated through direct interaction with avocado and mango growers in south Florida through presentations at growers' associations and scientific societies meetings, and virtually using social platforms. In HI results was communicated with project farm collaborators and with the mango industry.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Chang Y, Harmon PF, Treadwell DD, Carrillo D, Sarkhosh A and Brecht JK (2022) Biocontrol Potential of Essential Oils in Organic Horticulture Systems: From Farm to Fork. Front. Nutr. 8:805138. doi: 10.3389/fnut.2021.805138
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Chang, Y., Sarkhosh, A., Brecht, J. (2021). Evaluation of thyme oil vapor for control of
postharvest gray mold on blueberry. In: Proc. Fla. State Hort. Soc. 135:174.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2023
Citation:
Ga��n-Betancur L., Crane, J. H., Schaffer, B., Sarkhosh, A., Vargas, A. I., Melcon, R., and Gazis, R. (2022) Achieving sustainable anthracnose management in organically grown avocado and mango orchards in south Florida. In: Proc. Fla. State Hort. Soc. 135: Accepted.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Chang, Y., Sarkhosh, A., Brecht J. (2022). Thyme oil vapor postharvest treatment for decay control can cause damage to peach and blueberry fruits. ASHS Annual Conference, Chicago, IL.
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Progress 09/01/20 to 08/31/21
Outputs
Target Audience:Project team in their states have been communicating with project farm collaborators via phone, email, and farm visits (12 farms). Communication of (preliminary) project results is anticipated to begin in year 2. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Three postdocs were recruited and trained to conduct experiments in lab, greenhouse and filed. The two in plant pathology have been investigating antifungal activity assays for Thyme Guard and Timorex Gold against pathogen in blueberry, peach, avocado and mango. A postdoc in entomology has been studying performance of commercial formulations of essential oils to control Lace bug in Avocado. A Ph.D. student was required and trained with hands on in pathogen isolation, growth and fruit inoculation to investigate performance of commercial formulations of essential oils to control postharvest decay in peach and blueberry. Two MS student were recruited and trained to work on filed evaluation commercial formulations of essential oils in peach and blueberry in South Carolina and Georgia. The student is scheduled to start fall semester of 2021. Subaward accounts were set up to initiate the project. Three biological scientists and 4 OPS have been gaining additional training to enhance their professional development in their position. How have the results been disseminated to communities of interest?At the annual team and advisory members meeting, project development was discussed. A poster titled "Mango and avocado anthracnose: A major challenge for organic fruit production in south Florida" was presented at 98th Southern Division Meeting/American Phytopathological Society in February 2021. An oral presentation tilted "Evaluation of thyme oil vapor for control of postharvest gray mold on blueberry" in Annual meeting of Florida State Horticultural Society in September 2021. Project team in their states have been communicating with project farm collaborators via phone, email, and farm visits (12 farms). Communication of (preliminary) project results is anticipated to begin in year 2. What do you plan to do during the next reporting period to accomplish the goals?Detached leaf/stem screening assays, leaves for the assay will be collected from greenhouse-grown fruit crops, using protocols based on Conner (2012). Efficacy fungicidal activity will be tested on container-grown plants in greenhouse. Testing EOs for controlling insects through laboratory bioassays will be performed. On-farm plant disease control efficacy of EOs will be determined using 2-3 product rates selected from objective one. The selected EO rates for each crop will be compared to standard growers' practices in the certified organic orchards. Postharvest fruit decay incidence, fruit quality, and sensory evaluation for all fruit crops as affected by treatments in the field (in situ) and in the lab (in vivo) will be determined. At the annual team meeting, advisory members will discuss project development, review project outputs and the annual evaluation summary and recommend changes. Presentations and extension activities with focus on the application of findings relevant to local outcomes.
Impacts
What was accomplished under these goals?
Obj.1: Blueberry and peach: The antifungal activity assays for Thyme Guard and Timorex Gold were carried out on Potato Dextrose Agar (PDA). Each product was added to autoclaved PDA (at the final EO concentrations of 0, 17.25, 34.5, 69, 138, and 276 µlL-1). These concentrations were chosen after preliminary assays that showed high growth inhibition with Thyme Guard amended PDA for a few of our isolates. The trial assays also showed isolate growth inhibition decreased after the third day. Overall 11 fungal isolates were tested. Three replicate plates for each concentration were used per isolate and two growth diameter measurements were taken for each test plate at 24h time interval until Day 3. Thyme Guard amended plates displayed high to complete inhibition of all isolates growth, especially on Day 1 and Day 2 and at EO concentration 138 and 276. In contrast, Timorex Gold seems to enhance isolates growth at all concentrations (hormosis), especially on Day 2 and 3 and at high EO concentrations. The EC50 estimates and R square values for our Colletotrichum isolates (T5-5-9-15, SY(one), MR1 and Mr2) tested against ThymeGuard and a graph showing the relative growth of the isolates when tested against Timorex Gold. The estimates for the rest of the tested isolates are in progress. Mango and Avocado: Sixty isolates of Colletotrichum spp., "anthracnose", were obtained from diseased tissues (fruits, leaves, and twigs) of avocado and mango in Florida, Hawaii, and California. Isolates that successfully produced spores on culture media were further purified as single-spore isolates, confirmed as Colletotrichum spp. by examination of morphological characters, and stored (-80°C). Pathogenicity tests were conducted to assess aggressiveness among the collection of Colletotrichum isolates from mango and avocado. The more aggressive isolates (5 per crop) will be used in the in vitro screening the fungicide activity of EOs, using the selected concentration ranges. Preliminary experiments, using two representative isolates, were conducted to select an adequate range of EOs concentrations for the in vitro the fungicide assays. The commercial formulations Thyme Guard and Timorex were diluted in sterile water and added to molten PDA at about 50°C to obtain final concentrations ranging from 0 (non-amended control) to 1200 μl.L-1, based on previous published postharvest experiments (Sarkhosh et al. 2017, 2018a,b). Five-millimeter diameter mycelial plugs were cut from the margin of 7-days old Colletotrichum colonies and were transferred to five replicate plates of each EOs concentration. Percent of fungal growth inhibition at each EOs concentration was calculated in relation to fungal growth observed in the non-amended controls at 7 days after inoculation. Fungal growth inhibition values were fitted to a four-parameter log-logistic model using the 'drc' package in the software RStudio (Ritz et al. 2015) to estimate the effective concentrations causing 50% inhibition of mycelial growth (EC50 values), as well as the minimum inhibitory concentrations (MIC) per EO. Fungal growth was not observed at concentrations equal or higher than 652 μl.L-1, 300 μl.L-1, and 300 μl.L-1, for the commercial formulation Thyme Guard, and the pure formulations of thyme oil and savory oil, respectively. Interestingly, the MIC concentration value observed for Thyme Guard only contains about 150 μl.L-1 of thyme oil (i.e., 23% active ingredient). If compared to the MIC observed with the pure formulation of thyme oil (i.e., 300 μl.L-1), the concentration of thyme oil required to achieve MIC with the product Thyme Guard is a half time lower. This result might be partly due to a potential fungicide action of the additional inert ingredients present in the Thyme Guard formulation used (e.g., sodium citrate).On the other hand, fungal growth was observed in all the concentrations tested for Timorex which contains 12.5% tea tree oil. Additional tests using higher concentrations of Timorex showed that the MIC for this commercial product are higher than 27,000 μl.L-1 (≈ 3,400 μl L-1 tea tree oil). Timorex at concentrations of 27,000 μl.L-1 and 54,000 μl.L-1 (2x and 4x the highest rate recommended in the label, respectively) were sprayed onto leaves of potted mango and avocado plants to further explore potential phytotoxicity damage at rates ≥ 27,000 μl.L-1. At these two rates, phytotoxicity was observed on leaves and flowers, on both crops. Therefore, the Timorex manufacturer recommended high rate (i.e., 13,500 μl.L-1 Timorex will be considered as the highest concentration to be evaluated in next experiments with this compound. Detached leaf assays: Target spot on blueberry: Plant material (Optimus & Sentinel varieties) were ordered and arrived late July. However, these are currently too small to use for detached leaf assays. They were transplanted and are currently growing in the greenhouse. Half are to be fertilized, while the other half are to be used for modified leaf assays using the whole plantlets. Although delayed by the slow growth and sporulation of our Corynespora isolate, the assays will be performed soon. Rust on peach: Clean leaf material (no fungicide) is needed as soon as possible. Rust spores also need to be collected before September for the assays to be completed. Performance of commercial formulations of essential oils to control the Avocado Lace bug The widely used conventional insecticides Danitol® and Imidacloprid® were highly effective in controlling ALB. ThymeGuard® (Thyme oil) and Stylet® (mineral oil) were the most effective alternatives to conventional pesticides for ALB control. The essential oils Agropest®, Timorex®, and Armorex®, showed low insecticidal activity against ALB. ThymeGuard® and Stylet® should be reapplied to obtain better control. The essential oil ThymeGuard® is an alternative to conventional insecticides to manage the avocado lace bug. However, effective control may require repeated applications. Obj. 2: High and low rates of Timorex were used for two applications at 1.5 months interval (using 4 gal jugs and compressor-based spray system). The same system was used for Thyme Guard at recommended high label rate and ~3x rate at the first application. On blueberry, a Higher (5x) rates of both Timorex and Thyme Guard are detrimental to fruit development and quality in blueberry. In peach, higher (~3x) rate of Thyme Guard also seems to have minimal effect on tree flowering/foliage emergence/fruit. ThymeGuard and Timorex treatment rates were the highest and lowest recommended concentrations and a concentration in the middle for mango and avocado. Phytotoxicity data was collected weekly from the time of spraying to 1 week after spraying was completed. No phytotoxicity was observed in any of the treated branches. Obj. 3: Trees were sprayed to runoff (4.5 gal/tree) at 100 psi with a handgun sprayer on 27 May 5 Jun, and 11 Jun. Decay was calculated as a percentage 3 and 7 days postharvest (dph). OSO 5%SC applied at 13 fl oz reduced preharvest but not postharvest brown rot compared to the control, however, in combination with 0.25% ThymeGuard no reduction in disease was recorded either preharvest or postharvest. OSO 5%SC caused significant defoliation of older leaves leading to blind nodes on branches and its combination with 0.5% PureSpray (a highly purified mineral oil) exacerbated this effect. The mixture with 0.25% ThymeGuard, however, did not cause this negative effect. Obje. 4: Project team in their states have been communicating with project farm collaborators via phone, email, and farm visits (12 farms). Communication of (preliminary) project results is anticipated to begin in year 2.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Mango and avocado anthracnose: A major challenge for organic fruit production in south Florida
Thais G. Egreja, Jonathan Crane, Bruce Schaffer, Ali Sarkhosh, & Romina Gazis. (2021). Mango and avocado anthracnose: A major challenge for organic fruit production in south Florida.
The 98thannual meeting of the American Phytopathological Society, Southern Division,virtually from February 15-19, 2021.
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