A Study of Botryosphaeria Ribis on Willow

SUMMARYA disease of willow caused by Botryosphaeria Ribis is characterized by the presence of cankers on the twigs, larger branches, and trunk. Successive blighting of the branches eventually results in the death of the tree.A single stroma of this organism on willow may simultaneously bear conidia, microconidia and ascospores. The microconidia are probably spermatia. Cultures derived from conidia are similar to those originating from ascospores, and from both, the Dothiorella stage may be produced.The development of the conidia, asci and ascospores of B. Ribis has been studied cytologically. The conidia are multinucleate but are borne by uninucleate conidiophoral cells. The development of the nuclei within the ascus is like that of other Ascomycetes. The ascospores are uninucleate when delimited but become multinucleate as they mature. For a period following germination the hyphal cells also are multinucleate.