FUNGAL PATHOGENS OF EUPHORBIA-HETEROPHYLLA AND EUPHORBIA-HIRTA IN BRAZIL AND THEIR POTENTIAL AS WEED BIOCONTROL AGENTS

A two-year survey of the fungi associated with two important congeneri c pantropical weeds, Euphorbia hetero-phylla and E. hirta, was conduct ed in part of their native range in southern Brazil. Sampling was conc entrated mainly in Rio de Janeiro State and ten species were identifie d as pathogens of these weeds. Two taxa, Botrytis ricini and Uromyces euphorbiae, were common to both weed hosts. Alternaria euphorbiicola, Bipolaris euphorbiae, Melampsora sp., Oidium sp. and Sphaceloma poinse ttiae were recorded only from E. heterophylla, whereas Colletotrichum gloeosporioides, Sphaceloma sp. and Sphaerotheca filliginea were restr icted to E. hirta. Botrytis ricini and Colletotrichum gloeosporioides are new records for E. hirta, and Alternaria euphorbiicola and Sphaero theca fuliginea are new host records for Brazil. Bipolaris euphorbiae, previously identified as Helminthosporium sp., is considered to be th e correct name for the causal agent of a major disease of E. heterophy llum in Brazil. The potential of these pathogens as biocontrol agents is discussed and the mycobiota associated with both these weeds worldw ide is reviewed.