Botryodiplodia dieback of Mimosa pigra, a noxious weed in northern Australia

Widespread dieback of the introduced noxious weed Mimosa pigra was observed during the dry months in monsoonal northern Australia. Stems were girdled by reddish‐brown lesions that generally originated from leaf axils. Botryodiplodia theobromae was consistently isolated from the lesions and was shown to cause the symptoms. It is suggested that the occurrence of dieback is linked with the establishment of a stem‐boring moth introduced as a biological control agent for M. pigra.