Komal K Sekhon,* Daniel D MacLean, and Sonet Van Zyl
*Fresno State University, Department of Viticulture and Enology, 2360 E. Barstow Avenue, M/S VR89, Fresno, CA, 93740 (kmlksekhon@mail.fresnostate.edu)

Retail preferences have increased table grape clamshell packaging and moved away from standard polyethylene bags (polybags). While still the minority, this shift in industry practice opens new opportunities for postharvest control of fungal decay pathogens. Current harvesting and handling practice include field-packing into polybags to minimize handling of the grapes. This practice helps manage humidity while reducing hairline cracking and mechanical damage to the grape skin. Clamshell packaging in packing houses allows inclusion of liquid fungicide with forced-air tunnel drying to control postharvest pathogens. Fungicide Candidate A (FCA) is a novel fungicide that was evaluated in a liquid application compatible with clamshell packaging as an alternative to potassium metabisulfite (KMBS) pads or sulfur dioxide fumigation. Ivory and Autumn King cultivars were artificially inoculated by spraying a spore suspension of 1 × 105 spores/mL Botrytis cinerea or 2 × 104 spores/mL Penicillium expansum uniformly to the fruit surface. An air-assisted research sprayer replicating commercial packing lines was used to apply FCA to unlidded clamshells of freshly-harvested grapes. FCA was evaluated in rates from 0 to 10 mg active ingredient per kg fruit compared to the commercial fungicide standard of KMBS pads. FCA treatments significantly improved disease control over the KMBS pad, with high rates producing 100% control. No phytotoxicity was observed from application of FCA and there was no grape rachis browning after 21 days in cold storage and 14 days at shelf life. As customer preferences change from current standard practices, it is crucial to understand the benefits of new packaging and how the industry can adjust quickly to meet growing demands. FCA is only one of many potential candidates for new liquid applications for fungal decay control as commercial handling practices of table grapes move from field to the packing line.

Funding Support: AgroFresh Solutions, Inc