GROWTH AND SURVIVAL OF VERTICILLIUM-CHLAMYDOSPORIUM GODDARD, A PARASITE OF NEMATODES, IN SOIL

Selective media for the isolation of the nematophagous fungus, Verticillium chlamydosporium, are described These enabled densities > 500 colony forming units (CFU) g-1 soil to be reliably estimated. However, there was little relationship between estimates of the Verticillium biomass in a sterilized soil and the numbers of CFU which developed on the selective media. The growth and survival of the fungus infield soils were studied and estimates of the numbers of CFU in soils in which cyst-nematode multiplication was suppressed were greater than in those in which the nematode multiplied. Isolates of the fungus differed in their ability to proliferate in soil, but some increased rapidly from applications of chlamydospores or a mixture of hyphae and conidia in alginate granules containing wheat bran. The energy source (wheat bran) was essential for the establishment of the fungus from granular applications. Numbers of CFU greatly exceeded those of chlamydospores, but there was considerable variation in the relationship in different soils. Some isolates of V. chlamydosporium proliferated in soil and survived in considerable numbers for at least 3 months. Hence, pre-cropping applications of the fungus should survive long enough to kill nematode eggs and females that develop on roots of spring-sown crops.