Pathogenicity and host range of Pseudocercospora fumosa, a potential biological control agent for moth plant (Araujia hortorum) in New Zealand.

The South American vine Araujia hortorum (Apocynaceae) was introduced as an ornamental species in several countries and has since become an invasive weed in many of them. In New Zealand it has been targeted for classical biological control, and this motivated field surveys for fungal pathogens in its native range in Argentina. A disease was frequently encountered in the field causing extensive damage to foliage, as well as stems and fruits. The fungus found in association with the symptoms was identified as Pseudocercospora fumosa. A detailed description of the fungus and the disease is provided. Pathogenicity tests were conducted, and Koch's postulates fulfilled. Host range tests were conducted on species within the Apocynaceae. Four of these, belonging to the same subtribe as A. hortorum, were found to be susceptible to the disease, while others less related ones were not. Pseudocercospora fumosa was observed to be able to cause severe disease on its host and to be highly specific. It is therefore proposed as a potential biological control agent against A. hortorum in New Zealand.