Postharvest disease control in lychee

Abstract

Lychee (Litchi chinensis Sonn.) is a highly perishable commodity. Internationally, sulphur dioxide fumigation, modified atmosphere packaging, fungicide and hot water dips, and cool storage are used to reduce disease losses. This paper summarizes results of screening work with these treatments and comments on their current utility. Hot benomyl was equally effective at 50 and 52°C in controlling postharvest disease lesions (caused by Alternaria alternata, Phomopsis sp. and other fungi) on lychee cv. Bengal during storage at 5°C for up to 30 days. Since this work has been completed, benomyl has been withdrawn as a postharvest fungicide but thiabendazole has been an effective replacement. Hot benomyl appeared less effective on cv. Kwai Mai Pink, where heat damage of the pericarp interacted with disease expression. Prochloraz also provided good disease control but unfortunately caused tainting. Sulphur dioxide slow release pads provided good disease control, but caused bleaching of the pericarp. Colour gradually returned after removal of the sulphur dioxide pads. Penicillium spp. infected fruit that were not completely fumigated. Cool storage (5°C) per se delayed disease expression on cv. Bengal for up to 16 days. A. alternata, Colletotrichum gloeosporioides, Colletotrichum acutatum and Pestalotiopsis sp. were recorded as pathogens of lychee fruit.