INTERACTIVE EFFECTS OF ROTYLENCHULUS RENIFORMIS AND PHYTOPHTHORA PALMIVORA 1 ON PAPAYA ( CARICA PAPAYA L.) SURVIVAL AND GROWTH IN GREENHOUSE POTS

Individual and interactive effects of the pathogen complex, Rotylenchulus reniformis and Phytophthora palmivora , were investigated on papaya ( Carica papaya ) grown in greenhouse pots (10-cm-diam) for 3-4 months. P. palmivora was a more virulent pathogen than R. reniformis and caused moderate to severe mortality (27-73%) at an inoculum density of 1,000 zoospores per pot. No lethal or sublethal effects of P. palmivora on papaya at lower inoculum densities were evident. R. reniformis stimulated papaya growth at inoculum densities below 500 juveniles per pot and only moderately decreased growth (1-2 g loss in plant dry weight for every log10 increase in initial population density) at higher densities (1,000-10,000 juveniles per pot). Synergistic interactions were observed between the two pathogens on papaya mortality, root ratings, and plant dry weight in some experiments. R. reniformis predisposed papaya to attack by P. palmivora , although P. palmivora had indirect negative effects on R. reniformis by reducing nematode reproduction through reduced quantity and quality of host roots. Four-wk-old plants were more susceptible to the pathogen complex, especially to P. palmivora , than 8-wk-old plants.