COMPARATIVE MORPHOLOGY AND PATHOLOGY OF CALONECTRIA-THEAE AND CALONECTRIA-COLHOUNII IN HAWAII

Calonectria theae is distinguished from C. colhounii by perithecial co lor, number of ascospores in an ascus, longer stipes, longer conidia, and the formation of a second conidial type that is extraordinarily lo ng, angular, and borne on simple, submerged, dichotomously branching c onidiophores. Both species were isolated from ohia (Metrosideros colli nus), M. excelsus, and sentry palm (Howea forsteriana). C. theae was a lso isolated from leather leaf fern (Rumohra adiantiformis) and Streli tzia, while C. colhounii isolates were obtained from Eucalyptus, Leuco spermum, and Chrysalidocarpus lutescens. All tested isolates of both C alonectria spp. were pathogenic to ohia, an important native tree spec ies in Hawaiian forests. Both species killed apical shoots, and caused leaf spotting, blighting, and subsequent defoliation. Symptomatically , the diseases caused by these species are indistinguishable on ohia. This disease poses a potential threat to native forests.