NAME OF THE ORGANISM: Phytophthora x cambivora {Phytophthora cambivora} (PHYTCM)

Evaluation continues

This plant species has no EPPO PM4 Standards, and the pest is not mentioned in other PM4 standards

Candidate

Pistacia vera has been identified as a host of Phytophthora cambivora [only?] in artificial inoculations tests (Kouyeas, 1973 in CABI).
The main pathway of P. x cambivora is the transport of contaminated substrates by human activities: tillage practices and vehicle movement along the rural road network have been associated with disease spread (Vannini et al. 2005; Martins et al. 2007). Cryptic dissemination of Phytophthora inoculum with soil or soil-like substrates plays a major role in epidemiology of the associated diseases (Jung et al., 2009).
Phytophthora cambivora can live as a saprophyte in the soil, feeding on salts and dead organic material, often in competition with other microorganisms. In Europe, P. cambivora is widespread in the soil. Infection is favored by moist and moderate climates. P. cambivora survives in the soil in the form of mycelium, sporangia, zoospores and oospores. It is frequently found in soils with impeded drainage, due to a high water table or to a particular soil texture. Soils may drain poorly because they are compact (fine-textured silty or sandy) or clayey (Day, 1938; Erwin & Ribeiro, 1996, cited from CABI, 2021).
Water is a pathway: Disease outbreaks are associated with local climatic parameters such as precipitation, temperature, pH (Vettraino et al. 2005) and landscape heterogeneity, which facilitates inoculum movement along creeks and natural drainage channels (Vannini et al. 2010).
Plants for planting are a pathway (Jung & Blaschke 2004; Jung et al. 2009): Phytophthora inoculum may be transported from nurseries in latently infected host tissues and substrates (soil, potting mix), even associated with non-host plants. Because of the wide host range and longevity of inoculum sources in the environment, planting material (transplants) are generally not considered to be the main pathway for introduction under outdoor field conditions. The Fruit SEWG noted that the occurrence of temperatures during a period below 0°C may not be a limiting factor as is the case for P. cinnamomi (C. cambivora seems better adapted to cooler conditions, see summarysheet for P. cinnamomi on C. sativa). However, although it has a high persistence capacity in soil, where it can live saprophytically, it seemed that in central Italy it has difficulties to survive in soil for most of the year, which the authors attribute to its inability to produce oospores in the population analysed (sexual spores are formed after the union of mycelium of types A1 and A2; in that area only type A2 is present) (only some oospores may be formed as result of selfing stimulated by ubiquitous soil fungi). Furthermore, chlamydospores are not known to be formed by this species. The above considerations suggest that P. cambivora has the ability to spread from infected roots and establish new infections for only a limited period of the year, when climatic conditions are favourable to the formation, release and survival of zoospores (CABI, 2021; Vettraino et al., 2001), making plants for planting a significant pathway in such particular situations.
True seeds are not known to carry P. cambivora (CABI, 2021).