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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Citrus and Other Subtropical Products Research » Research » Publications at this Location » Publication #412395
Research Project: Determination of Flavor and Healthful Benefits of Florida-Grown Fruits and Vegetables and Development of Postharvest Treatments to Optimize Shelf Life an Quality for Their Fresh and Processed Products

Location: Citrus and Other Subtropical Products Research

Title: Preharvest-applied fungicides for postharvest Diplodia stem-end rot control on grapefruit

Author
item ZHANG, JIUXU - University Of Florida
item YAN, JIAQI - University Of Florida
item MYERS, MONTY - University Of Florida
item HU, CUIFENG - University Of Florida
item DIAZ, EDISON - University Of Florida
item CANO, LILIANA - University Of Florida
item Bai, Jinhe
item Plotto, Anne
item Zhao, Wei
item RITENOUR, MARK - University Of Florida

Submitted to: Florida State Horticultural Society Meeting
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2024
Publication Date: 12/31/2024
Citation: Zhang, J., Yan, J., Myers, M., Hu, C., Diaz, E.A., Cano, L.M., Bai, J., Plotto, A., Zhao, W., Ritenour, M.A. Preharvest-applied fungicides for postharvest Diplodia stem-end rot control on grapefruit. Florida State Horticultural Society Meeting. 136:164. 2024.

Interpretive Summary:

Technical Abstract: Diplodia stem-end rot (SER), caused by Lasiodiplodia spp., is an important postharvest decay on fresh citrus in Florida. The epidemic of Huanglongbing (HLB) in Florida causes citrus tree decline resulting in more dead wood that significantly increases Lasiodiplodia populations and preharvest fruit infection, leading to increased postharvest Diplodia SER. Evaluations of foliar-applied chemicals to suppress preharvest fungal populations and fruit infection to reduce subsequent postharvest Diplodia SER were conducted in multiple grapefruit groves over four seasons (2019-2023). Overall, results obtained from the multiple groves over four seasons showed that: Graduate A+ (fludioxonil + azoxystrobin), effectively and consistently reduced Diplodia SER when used at postharvest rates, which are higher than what would be allowed for preharvest applications. Abound (azoxystrobin), Headline (pyraclostrobin), Cannonball WG (fludioxonil), Mertect 340F (thiabendazole), Quadris Top (azoxystrobin + difenoconazole), Luna Sensation (flupyram + trifloxystrobin) and Veltryma (pyraclostrobin + mefentrifluconazole) moderately reduce Diplodia SER but were not consistent. Topsin 4.5 FL (thiophanate-methyl) consistently showed the best Diplodia SER control in all tests, however, it is not available for commercial use since efforts by the registrant to obtain an EPA label for citrus were abandoned in 2009. Miravis Prime (fludioxonil + pydiflumetofen) consistently reduced Diplodia SER incidences in all tests, and it also showed good activity for decay control during the simulated commercial postharvest fruit cold storage. However, it is not currently registered for use on most citrus. The registrant has been contacted in efforts to obtain a US EPA label for use on grapefruit and other citrus not currently on the label to provide an additional tool for Diplodia SER control.