Pest of the Month – Phytophthora diseases (spp.)

Category name: Fungi

Importance: Major1610 Phytopthora

Symptoms: Phytophthora pathogens cause many different diseases and disease symptoms on a wide range of hosts. They include root rot, collar rot, tree canker, stem lesions, bud rot, heart rot, leaf blight, fruit rot, tuber and corm rot. They cause wide scale economic losses in horticulture and in the ornamental, forestry and pastoral industries. Some species have the potential to destroy natural ecosystems.

Transmission: Depending on the species they can be transmitted by several means. Sporangia can be dispersed by wind and rain, zoospores by surface and irrigation water; hyphae, chlamydospores and oospores can be carried in infected plants, plant debris, seed and cuttings or in infested soil on implements, shoes, vehicles and clothing. They are also carried by animals (ingestion or transport of infested soil).

Favoured by: Phytophthora pathogens thrive in humid and wet conditions. Soil temperatures are important.

Host range: Some species have a wide host range (e.g. P. cinnamomi) whereas others only infect a single host species (P. fragariae var. rubi).

More Information: Detailed coverage of Phytophthora is contained in the NGIA Pest Fact Sheet: Phytophthora diseases – problematic in the nursery and beyond, which is available online.

Further industry pest information is available at

An initiative of the National Nursery Industry Biosecurity Program (NY15004) and the ‘Building the resilience and on-farm biosecurity capacity of the Australian production nursery industry’ Project (NY15002).