ADDITIVE EFFECTS OF MELOIDOGYNE-ARENARIA AND SCLEROTIUM-ROLFSII ON PEANUT

Field observations have suggested that infection of peanut by Meloidog yne arenaria increases the incidence of southern blight caused by Scle rotium rolfsii. Three factorial experiments in microplots were conduct ed to determine if interactions between M. arenaria and S. rolfsii inf luenced final nematode population densities, incidence of southern bli ght, or pod yield. Treatments included four or five initial population densities of M. arenaria and three inoculum rates of S. rolfsii. Fina l nematode population densities were affected by initial nematode dens ities in all experiments (P = 0.01) and by S. rolfsii in one of three experiments (P = 0.01). Incidence of southern blight increased with in creasing inoculum rates of S. rolfsii in all experiments and by the pr esence of the nematodes in one experiment (P = 0.01). Pod yield decrea sed with inoculation with S. rolfsii in all experiments (P = 0.05) and by M. arenaria in two of three experiments (P = 0.05). In no experime nt was the interaction among treatments significant with respect to fi nal nematode population densities, incidence of southern blight, or po d yield (P = 0.05). The apparent disease complex between M. arenaria a nd S. rolfsii on peanut is due to additive effects of the two pathogen s.