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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Food Quality Laboratory » Research » Publications at this Location » Publication #422180
Research Project: System Approaches Using Genomics and Biology to Manage Postharvest Fruit Decay, Antimicrobial Resistance, and Mycotoxins to Reduce Food Loss and Waste

Location: Food Quality Laboratory

Title: Colletotrichum species causing Glomerella leaf spot and apple bitter rot in the southeastern United States exhibit disparities in relative frequency, morphological phenotype, and QoI sensitivity

Author
item JOHNSON, KENDALL - Dlf North America
item DOUGLAS, RACHEL - North Carolina State University
item BRADSHAW, MICHAEL - North Carolina State University College Of Veterinary Medicine
item BRANNEN, PHILLIP - University Of Georgia
item Jurick Ii, Wayne
item VILLANI, SARA - North Carolina State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2025
Publication Date: 3/17/2025
Citation: Johnson, K., Douglas, R., Bradshaw, M.J., Brannen, P.M., Jurick Ii, W.M., Villani, S. 2025. Colletotrichum species causing Glomerella leaf spot and apple bitter rot in the southeastern United States exhibit disparities in relative frequency, morphological phenotype, and QoI sensitivity. Plant Disease. 109(3):579-592. https://doi.org/10.1094/PDIS-05-24-1006-RE.
DOI: https://doi.org/10.1094/PDIS-05-24-1006-RE

Interpretive Summary: Colletotrichum species cause apple bitter rot on fruit and leaves in the field and during storage that causes major losses in the United States. The fungus is controlled by fungicides and growers have requested more research to optimize their specific application and timing. This is the first study to systematically evaluate and optimize preharvest sprays that resulted in lower disease and will immediately impact fruit production in North Carolina with programs that can protect fruit finish and reduce losses. Findings from the study can also be extrapolated to other apple production areas where bitter rot of apple fruit is problematic.

Technical Abstract: Glomerella leaf spot (GLS) and bitter rot (BR) caused by Colletotrichum species are the most economically devastating fungal diseases on apples in North Carolina. Fungicide efficacy experiments investigating multi- and single-site active ingredients were conducted in a ‘Gala’ research orchard in 2017, 2018, and 2019. Fungicides were applied in non-rotational programs from petal fall (PF) through ninth cover (2017), thirteenth cover (2018), and twelfth cover (2019). The incidence of GLS, pre-harvest BR, and post-harvest BR along with GLS severity was significantly lower for programs in which the QoI fungicide, pyraclostrobin (Cabrio EG), the QoI/SDHI premix fungicide, pyraclostrobin and fluxapyroxad (Merivon), and captan (Captan 80 WDG) were applied. The programs of pyraclostrobin with fluxapyroxad and captan also resulted in a significantly lower GLS severity. Fungal isolates were collected from disease leaf and fruit tissue and identified as Colletotrichum chrysophilum .