Beech water mold
Phytophthora plurivora
Phytophthora plurivora is a highly pathogenic oomycete (water mold) and a primary driver of beech decline in Europe. It primarily attacks the fine root system, severely impairing the tree's ability to absorb water and nutrients. Infected trees often exhibit 'bleeding' bark cankers at the base of the trunk and progressive crown thinning. The pathogen spreads via motile zoospores in soil water, particularly under warm and moist conditions.
Details
Identification
Microscopic identification of sporangia and oospores; field identification via dark exudates on the trunk ('bleeding') and necrotic fine roots.
Diet
Absorptive nutrition as a parasite; extracts carbohydrates and nutrients from the host tree (mainly Fagus sylvatica) via mycelial growth.
Overwintering
Survival as thick-walled oospores or chlamydospores in the soil or within infected plant tissue.
Ecology
Ecological role
Significant forest pathogen; regulates beech population density and influences natural forest regeneration.
Natural predators
Soil microorganisms (e.g., certain bacteria and predatory fungi) capable of decomposing oospores.
Competitor species
Other Phytophthora species such as P. cambivora; saprotrophic soil fungi.
Threats
Climate change (increase in heavy rainfall events and mild winters favors dispersal).
Scientific profile
Profile
Distinguishing features
Semipapillate, mostly ovoid sporangia (approx. 45 x 30 µm) produced sympodially on sporangiophores. Homothallic with spherical oogonia and predominantly paragynous antheridia. Molecularly distinguished from Phytophthora citricola via ITS region sequencing (Jung et al. 2009).
Habitat
Beech forests, mixed deciduous forests, nurseries, parks, and riparian vegetation; especially in areas with periodic waterlogging.
Reproduction
Sexual via thick-walled oospores (resting spores for survival); asexual via sporangia that release motile, biflagellate zoospores under saturated conditions.
Protection & threats
Status not on standard scale
Main threats
Not threatened; the species itself poses a threat to the biodiversity of native forests.
Conservation measures
Prevention of dispersal by cleaning footwear and machinery; use of certified Phytophthora-free planting stock; improvement of soil structure to avoid waterlogging.