Pseudocercospora lonicerigena a leaf spot fungus on the invasive weed Lonicera japonica in Brazil

Abstract

Lonicera japonica (Japanese honeysuckle), a plant of Asian origin introduced as an ornamental into many countries, has become an invasive weed in some exotic situations, such as in southern Brazil. Classical biological control (CBC) with natural enemies collected in the centre of origin is considered to be the best alternative for sustainable management of L. japonica. In the context of this strategy, previous knowledge of the natural enemies already present in the target area is of great importance in order to avoid un-necessary introductions of CBC agents from the weed’s native range. Recently, examination of populations of L. japonica in localities in the Brazilian states of Rio de Janeiro and Paraná revealed the presence of leaf spots consistently associated with a cercosporoid hyphomycete. A molecular and morphological study of this fungus led to its recognition as Pseudocercospora lonicerigena. There were few differences when the Brazilian isolate was compared with a strain found in North America. This is the first report of this fungus in Brazil. The fungus was isolated in pure culture and inoculation of healthy leaves of L. japonica eventually led to leaf yellowing and necrosis, indicating that P. lonicerigena is not highly pathogenic, as evidenced by the continuing advance of this weed in southern Brazil. Therefore, the introduction of additional co-evolved natural enemies collected in Asia, perhaps piggy-backing on an ongoing project already underway in New Zealand, will be necessary to control this invasive alien weed in Brazil.