Efficacy of Pre-harvest Fungicide Applications and Cold Storage for Postharvest Control of Botrytis Fruit Rot (Gray Mold) on Red Raspberry

Abstract

Applications of the fungicides Elevate 50WG and Switch 62.5WG to red raspberry prior to harvest were evaluated for post-harvest control of fruit rot, caused by Botrytis cinerea. Fungicides were applied three times during bloom only, three times pre-harvest (post-bloom) only, or six times full season (bloom through harvest), and symptomless fruit (at harvest) were incubated for 8 days in either cold storage (4°C) or at room temperature (23°C). Without fungicide, between 6 and 29% of the fruit had rot symptoms after 2 days of storage at room temperature over the 2 years of testing; after 8 days, 74 and 85% of the fruit had symptoms at room temperature. Zero and 12% of fruit had symptoms with 2 days of cold storage when plants were not treated with fungicide, and rot incidence increased to 9 and 60% at 8 days of cold storage over the 2 years. All fungicide treatments significantly reduced post-harvest fruit rot compared to the control (six water sprays). Applications of fungicide only at bloom generally had higher fruit rot incidence than found for the pre-harvest and full season fungicide programs. Results indicate that pre-harvest (post-bloom) fungicide sprays are beneficial for control of post-harvest Botrytis fruit rot, especially when coupled with cold-temperature storage.Accepted for publication 8 August 2008. Published 15 October 2008.