Survival, dissemination, ingress and infection of the orchid strain of Phytophthora palmivora (Butl.) Butler on Vanda lamellata Lind.
1985
Ros, L.B.
The survival of the fungus was influenced by the moisture content of the soil during storage. In general, the fungus survived longer in soil with a high moisture content. Its survival was prolonged further under sterile soil condition. Under the most favorable storage conditions, the fungus persisted in soil for 7 months and 6 to 8 weeks only under adverse conditions. Rain drops appeared to be the most important means of disseminating the fungus at short distances. Indirect evidence to implicate the insects in the acquisition of the fungus had been obtained. Wind as simulated by an electric fan did not cause dispersal. Direct penetration by zoospores on intact tissues was not observed. Only wounded portions of the leaf tissues and stomatal openings were penetrated and invaded. The fungus spread intercellularly and intracellularly, the former being the most frequently observed on invaded parenchymatous cells. Vascular bundles also appeared invaded. Invading hyphae within host tissues could reach as far as 40 mm away from water soaked areas of infected leaves
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