Biology of Phytophtoras

Phytophthora cinnamomi and P. cambivora are species of oomycetes, pathogenic to a large number of tree species (conifers and broadleaves) and ornamental plants. They infect the fine roots of their host plants by mobile spores called zoospores. These spores with two flagella are released under favourable moisture and temperature conditions. After germination, the mycelium of P. cinnamomi and P. cambivora invades the root tissue (Figure 1).

In the necrotic roots, these oomycetes rapidly form new zoospores that can infect other trees, from close by, resulting in an outbreak distribution of diseased trees in the plot (Figure 2). P. cinnamomi and P. cambivora can maintain and multiply in the soil. Dispersal of these pathogens in the soil is favoured by excess water. They are also spread by infected plants and substrates. It is therefore crucial to check the health of the plants used for any new planting.