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  • Author or Editor: Cristi Palmer x
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Botrytis cinerea is one of the problematic and notorious postharvest pathogens of bigleaf hydrangea (Hydrangea macrophylla) cut flowers. It causes flower blight, leaf blight, and stem rot, reducing the ornamental value (such as longevity, color, and texture) of flowers, ultimately making them unsalable. The objective of this study was to identify effective conventional fungicides and biorational products for botrytis blight management on bigleaf hydrangea cut flowers that can be easily and readily adopted by growers of ornamentals. Preventive preharvest whole-plant spray and postharvest dip treatment applications were used in this study. For the whole-plant spray applications, bigleaf hydrangea plants were sprayed with treatment solution 3 days before harvesting flowers. For the dip applications, cut flowers were dipped in treatment solutions after harvest. For both application types, flowers were inoculated with B. cinerea spores once treatment solutions dried. Flowers were stored in cold storage for 3 days and then displayed in conditions similar to retail stores. Botrytis blight disease severity, marketability of flower (postharvest vase life), phytotoxicity, and application residue were assessed in the study. Treatments showed variable efficacy in managing postharvest B. cinerea infection in bigleaf hydrangea cut flowers. Preventive preharvest whole-plant spray and postharvest dip applications of isofetamid and fluxapyroxad + pyraclostrobin significantly reduced the postharvest botrytis blight disease severity and area under disease progress curve (AUDPC) compared with the positive control (nontreated, inoculated with B. cinerea). When applied as a postharvest dip, the fungicide fludioxonil and biofungicide Aureobasidium pullulans strains DSM 14940 and DSM 14941 effectively lowered the disease severity and disease progress (AUDPC). These effective treatments also maintained a significantly longer postharvest vase life of bigleaf hydrangea cut flowers compared with the nontreated, inoculated control. The longer vase life may be attributed to lowered botrytis blight disease severity and the resultant proper physiological functioning of flowers.

Open Access

Magnolia trees (Magnolia sp.) are a popular choice for consumers when choosing flowering woody plants for landscapes. Magnolia species grow in a wide variety of both temperate and tropical locations. Southern magnolia (Magnolia grandiflora) is one of the more popular magnolias due to its pleasing aesthetics: large showy flowers in a range of colors and evergreen foliage. However, magnolias can be affected by algal leaf spot. Algal leaf spot is caused by Cephaleuros virescens, which is a widespread plant parasitic green alga. There has been little research on how to treat algal leaf spot on magnolia plants. This study focuses on identifying effective biological- and chemical-based fungicides for the management of algal leaf spot disease of magnolia plants. Two experiments were conducted in a randomized complete block design with six replications per treatment and a total of 12 treatments, including a nontreated control. The first experiment (Expt. 1) was conducted in a shade house (56% shade) at McMinnville, TN, using southern magnolia plants. The second experiment (Expt. 2) was conducted at a commercial nursery in McMinnvillle, TN, in a field plot planted with ‘Jane’ magnolia (Magnolia liliiflora ‘Nigra’ × Magnolia stellata ‘Rosea’). The algal leaf spot disease severity, disease progression, plant marketability and growth parameters were evaluated. In both experiments, all treatments reduced algal leaf spot disease severity and disease progress in comparison with the nontreated control. In Expt. 1, copper octanoate, copper oxychloride, chlorothalonil water-dispersible granules, chlorothalonil suspension concentrate, didecyl dimethyl ammonium chloride, azoxystrobin + benzovindiflupyr, hydrogen peroxide + peroxyacetic acid, and mono- and di-potassium salts of phosphorus acid + hydrogen peroxide reduced the disease severity and disease progress the most and were not statistically different from one another. In Expt. 2, azoxystrobin + benzovindiflupyr, didecyl dimethyl ammonium chloride, and copper oxychloride significantly reduced disease severity and disease progress (area under disease progress curve). Treatments had no deleterious effect on plant growth parameters such as height and width, and no phytotoxicity of applied treatments or defoliation was observed. Treated magnolia plants had better plant marketability compared with the nontreated control plants. The findings of this study will help growers to achieve better management of algal leaf spot disease on magnolia trees.

Open Access