SURVIVAL OF PHYTOPHTHORA-MEADII IN SRI-LANKAN SOILS

In laboratory tests, mycelium and sporangia of Phytophthora meadii survived in soil for about 3 weeks, whereas chlamydospores survived for 12 weeks. When petioles of rubber (Hevea brasiliensis) colonized by P. meadii were buried in soil, chlamydospores formed in the tissues after about 2 weeks and P. meadii could be reisolated up to 22 weeks after burial. Colonized petioles buried in soil in a rubber plantation decayed more rapidly than those in laboratory tests, and attempts to reisolate P. meadii after 18 weeks were unsuccessful, although chlamydospores were still visible. P. meadii was isolated most readily from soil in a rubber plantation during epidemics of pod and leaf disease, suggesting that sporangia from these sources maintained soil inoculum at a high level. Inoculum detected in soil before pod and leaf infection may have arisen from subclinical infections or from chlamydospores surviving in petioles from the previous season.