Behaviour of Phytophthora cinnamomi rands in different soils and water regimes

The effect of different soils, nutrient states and water regimes on the growth, sporulation and lysis of mycelial inocula of Phytophthora cinnamomi has been examined. It has been observed that the requirements for chlamydospore and sporangium production in soils are relatively non-specific with respect to soil type, pH, percentage organic matter and the presence or absence of an additional food source. In contrast to chlamydospore production, however, production of sporangia in soil depends on a sufficiently low water suction pressure. In some soils a low percentage water content or a water content well below field capacity did not necessarily inhibit sporangium production. The pathogen was a good competitor for pieces of both fresh and rotting Castanea sativa radicles. Trichoderma viride appeared to play a significant role in soil by lysing hyphae of P. cinnamomi and inducing it to produce oospores.