EFFECTS OF STERILE AND NONSTERILE LEACHATES EXTRACTED FROM COMPOSTED EUCALYPTUS BARK AND PINE-BARK CONTAINER MEDIA ON PHYTOPHTHORA SPP

Production of sporangia by Phytophthora cinnamomi, Phytophthora cryptogea, Phytophthora citricola, Phytophthora drechsleri and Phytophthora nicotianae var. nicotianae on Miracloth discs was compared in filter-sterilized and non-sterile leachates extracted from a pine-bark based container medium (NM) and a composted Eucalyptus-bark medium (CEB). Sporangial production of all species was suppressed in non-sterile CEB leachate; whereas, in sterile CEB leachate it was stimulated in comparison to the NM leachate. P. drechsleri and P. cryptogea appeared to require the presence of certain microorganisms to induce zoospore release. Chlamydospore production by P. cinnamomi was suppressed in CEB leachates. On cornmeal and water agar mixed with filter-sterilized or non-sterile leachate from NM and CEB, mycelial growth varied with leachate, agar type and Phytophthora species. Isolates within P. drechsleri and P. cinnamomi responded differently to the extracts.