Resistance in Capsicum Species and Cultivars to Colletotrichum scovillei and Implications for Fungicide Applications.

Abstract

Green fruit anthracnose caused by the fungus Colletotrichum scovillei is an emerging disease on various types of peppers (Capsicum spp.) in the eastern United States. Sixteen cultivars, representing 11 horticultural fruit types from four species of Capsicum, C. annuum, C. baccatum, C. chinese, and C. frutescens, were evaluated for potential fruit rot resistance to C. scovillei in replicated field plots in summer 2022 and 2023. Fruit was naturally inoculated by facilitating spread of conidia of C. scovillei with overhead irrigation from inoculated jalapeño fruit on plants located between plots into test plots. C. chinense cultivars Roulette and Carolina Reaper and C. frutescens cultivars Tabasco and Malagueta had significantly lower fruit disease incidence than the other 12 cultivars in both years. In a second experiment, conducted in fall 2022 and 2023, four C. annuum pepper types were treated or not treated with a preventative rotation of mancozeb and azoxystrobin at labeled rates. The fungicide treatment reduced fruit disease incidence fivefold compared to the nontreated control in both years. In the nontreated plots, the reduced susceptibility of jalapeño, New Mexico chili, and Italian frying peppers provided 50% fruit rot control relative to susceptible bell pepper. In fungicide-treated plots, however, mean percentage control was 80% for the non-bell cultivars. In 2022, marketable weight and number were fivefold greater on fungicide-treated plants than non-treated plants, but in 2023, yields were not affected by fungicides. C. frutescens may be useful as a source of resistance to develop new pepper cultivars that would help growers manage green fruit anthracnose.