Anthracnose Caused by Colletotrichum horii on Sweet Persimmon in Korea: Dissemination of Conidia and Disease Development

Abstract

Anthracnose disease caused by Colletotrichum horii (C. gloeosporioides), results in considerable economic damage to sweet persimmon in southern Korea yearly. This study deals with the life cycle of the pathogen in terms of seasonal fluctuations of spore dispersal and the development of disease based on field surveys, spore potential and fungal isolation. Anthracnose disease was observed first on twigs in the last week of May and reached an incidence of 1.2%. Subsequently, the disease increased rapidly and reached an incidence of 86% by the end of July. Infection of fruits started in mid-June (2.8%) and increased gradually to 64.4% by the end of July. In severely infected orchards, 46.2% of diseased fruits were dropped. The pathogen began releasing conidia in the first week of May and continued until the end of September. The maximum release of spores was observed in mid-July. To determine the optimal use of chemicals for control of anthracnose, the following spray programme was evaluated. Spraying two or three times resulted in 89.4 and 93% control, respectively, whereas spraying more than four times led to 100% control. In comparison, the disease rate of unsprayed trees was 89.8%. To control anthracnose effectively, it is recommended to take steps to eliminate inoculum sources in sweet persimmon orchards before spraying chemicals.