First report of stub dieback of poinsettia (Euphorbia pulcherrima) caused by Sclerotinia sclerotiorum in Vietnam

Stub dieback of poinsettia caused by Sclerotinia sclerotiorum is reported from Vietnam for the first time. It was discovered in potted plants in a polyhouse in Dalat, Lam Dong Province, in December, 2010. The disease was scattered throughout the greenhouse, but the incidence was low. Infection appeared to have occurred though the cut surface of the stub, where the stem had been pruned to encourage branching. Large irregular black sclerotia were present on some diseased stems. There was no evidence of apothecia in the affected pots, or elsewhere in the greenhouse. Consequently it is postulated that infection was caused by ascospores that drifted into the polyhouse after release from apothecia in adjacent fields. Sclerotinia head rot of polyhouse, and field-grown cabbages and lettuce, is a serious problem in the Dalat area.