Survival of Colletotrichum gloeosporioides on Stylosanthes scabra cv. Fitzroy during the dry season

Abstract

Infected stems of the tropical pasture legume Stylosanthes scabra cv. Fitzroy were assessed over two consecutive dry seasons to determine if Colletotrichum gloeosporioides survived as conidia on lesions formed during the previous wet season or as hyphae within infected tissue. In the second season, infected stem pieces placed on the soil surface (debris) and in a 15¦C incubator at the beginning of the dry season were assessed in addition to the material from living plants. Infective conidia were present in sufficient numbers to be detected in all but the initial sample in each season, and C. gloeosporioides could be isolated from lesions on plant tissue throughout both dry seasons. Conidium density on live stems was variable in the first season, where no rain fell until the onset of the wet season in mid-November. Conidia were present in similar densities on stems throughout the second dry season, when intermittent light rain fell during the assessment period. The mean density of conidia was significantly higher on live stems than on debris or stems stored at 15¦C. Large numbers of conidia were produced on stem pieces from living plants and debris after incubation under conditions conducive to sporulation. Conidia were, therefore, present or could be rapidly produced to initiate an epidemic once favourable conditions for dispersal and infection occurred.