Preliminary investigation of Pythium seedling root rot of oil palm.
Losses due to the disease in Malaysia (Sabah) during 1973-74 were 1.2-8.6%. Infection was initiated just after the beginning of the wet season but most affected seedlings did not succumb until the dry season. Leaf symptoms resemble those described for the blast seedling disease caused by Macrophomina phaseolina but the root decay is different; in P. root rot the rot usually extends into the bulb and the persistence of vascular strands typical of blast is absent. Infected oil palm nurseries yielded several P. spp.; P. vexans was most frequently isolated and P. splendens and P. myriotylum were recovered less frequently. All 3 spp. were pathogenic to oil palm seedlings in pot tests and inoculated seedlings were killed in 4-5 weeks. Co-infection with M. phaseolina has not been observed in Sabah. New progenies should be screened for resistance, although the disease is not at present causing severe losses.