Comparative performance of reduced-risk fungicides and biorational products in management of post-harvest Botrytis cinerea on hydrangea cut flowers

Authors: BIKA, RAVI - Tennessee State University; PALMER, CRISTI - Rutgers University; Alexander, Lisa; BAYSAL-GUREL, FULYA - Tennessee State University

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2020
Publication Date: 10/5/2020
Citation: Bika, R., Palmer, C., Alexander, L.W., Baysal-Gurel, F. 2020. Comparative performance of reduced-risk fungicides and biorational products in management of post-harvest Botrytis cinerea on hydrangea cut flowers. HortTechnology. https://doi.org/10.21273/HORTTECH04656-20.
DOI: https://doi.org/10.21273/HORTTECH04656-20

Interpretive Summary: Hydrangea macrophylla is one of the most important floral and nursery crops worldwide. In the floral industry, Botrytis cinerea is one of the most problematic and widespread post-harvest pathogens of hydrangea cut flowers. Infection with B. cinerea causes flower blight, leaf blight, and stem rot diseases which reduce the ornamental value (longevity, color, and texture) of flowers, ultimately making them unsalable. The invention and development of fungicides with new chemical compounds has played a crucial role in managing Botrytis blight; however, the number of fungicides registered for use on ornamentals has been decreased because of disease resistance development, environmental safety, and human health issues. Therefore, new products with novel modes of action that are less toxic and more socio-environmentally friendly must be sought. A team of USDA, Tennessee State University, and Rutgers University scientists found that pre-harvest whole plant spray and post-harvest dip application of Astun (isofetamid) and Orkestra Intrinsic (fluxapyroxad + pyraclostrobin) significantly reduced the post-harvest Botrytis blight disease severity and disease progress compared to non-treated, inoculated with B. cinerea (positive) control. The fungicide Medallion (fludioxonil) and biofungicide Botector (Aureobasidium pullulans strains DSM 14940 & DSM 14941) effectively lowered the disease severity and disease progress when applied as post-harvest dip treatment. These treatments also considerably maintained a longer post-harvest shelf life of hydrangea cut flowers compared to the non-treated, inoculated control flowers. Results of this study will provide ornamental growers with improved strategies to protect the quality and value of cut flowers and greenery.

Technical Abstract: Botrytis cinerea is one of the problematic and notorious post-harvest pathogens of hydrangea cut flowers and causes flower blight, leaf blight and stem rot. These diseases reduce the ornamental value (longevity, color and texture, etc.) of flowers, ultimately making them unsalable. The objective of this study was to identify effective fungicides and biorational products for B. cinerea management on hydrangea cut flowers that can be easily and readily adopted by ornamental growers. Preventive pre-harvest whole plant spray and post-harvest dip application of treatments were used in this study. For the whole plant spray application, hydrangea plants were sprayed with treatment solution three days before harvesting flowers. For the dip application, hydrangea cut flowers were dipped in treatment solution after harvest. For both applications types, flowers were inoculated with B. cinerea spores once treatment solutions dried. Flowers were stored in cold storage for three days and then displayed in conditions similar to retail stores. Botrytis blight disease severity, marketability (post-harvest shelf life), phytotoxicity and application residue were assessed in the study. Treatments showed variable efficacy in managing post-harvest B. cinerea infection in hydrangea cut flowers. Preventive pre-harvest whole plant spray and post-harvest dip application of Astun (isofetamid) and Orkestra Intrinsic (fluxapyroxad + pyraclostrobin) significantly reduced the post-harvest Botrytis blight disease severity and area under disease progress curve (AUDPC) compared to non-treated, inoculated with B. cinerea (positive) control. The fungicide Medallion (fludioxonil) and biofungicide Botector (Aureobasidium pullulans strains DSM 14940 & DSM 14941) effectively lowered the disease severity and disease progress (AUDPC), when applied as post-harvest dip treatment. These treatments also considerably maintained a longer post-harvest shelf life of hydrangea cut flowers compared to the non-treated, inoculated control flowers. The longer shelf life may be attributed to lowered Botrytis blight disease severity and the resultant proper physiological functioning of flowers.