INCIDENCE OF PHYTOPHTHORA FRUIT ROT ON FOUR DURIAN CULTIVARS IN DAVAO CITY, PHILIPPINES

A two-year study was conducted on a farm in Davao City to investigate the incidence of Phytopthora fruit rot on four commercial durian (Durio zibethinus Murr.) cultivars previously laboratory tested for their reaction to the disease using isolates of the pathogen, Phytophthora palmivora Butler. In Year 1, disease incidence was highest on cultivars ‘Alcon Fancy’ and ‘Arancillo’ at 10.7% and 9.9%, respectively. Lower levels of infection were observed for cultivar ‘Puyat’ (0.5%) and no infection was recorded for cultivar ‘Seri Kembangan’. The same trend was obtained in Year 2, further confirming previous laboratory infection test results. The incidence of infection for ‘Alcon Fancy’ was 47.3%, followed by ‘Arancillo’ (25.9%), ‘Puyat’ (12.6%) and ‘Seri Kembangan’ (2.1%). In monetary terms, the Year 1 total of 545 infected fruit was equivalent to a potential income loss of PhP 27,250. In Year 2, the total of 1,233 infected fruit translated into a potential income loss of PhP 49,320. ‘Alcon Fancy’, with the highest level of infection, contributed PhP 21,873, followed by ‘Arancillo’ (PhP 15,967), ‘Puyat’ (PhP 11,925) and ‘Seri Kembangan’ (PhP 1,295). Results of the study suggest that more disease management interventions are necessary for the more susceptible, but commercially preferred cultivars. Several fruit nursery operators in Davao City indicated that propagating ‘Alcon Fancy’ and ‘Arancillo’ seedlings is no longer profitable since knowledgeable farmers do not plant them anymore, citing high susceptibility to Phytophthora as the primary reason.