Plant & Food Research (PFR) Te Puke recently hosted two international scientists, Ana Pérez-Sierra from Spain and Trudy Paap from South Africa, who shared information from research projects on phytophthora species.

Phytophthora are soil-borne oomycetes or “water moulds” that can cause root and crown rot in a wide number of plants including kiwifruit.

Ana, from Instituto Valenciano De investigaciones Agrarias (IVIA) described how phytophthora species can transition from agricultural or horticultural settings to forestry and natural ecosystems and vice-versa, resulting in significant challenges across many global landscapes. P. ramorum (sudden oak death) is one example of a phytophthora species that has killed millions of oaks and other tree species throughout California.

Trudy who is now based at the University of Pretoria, presented on her work as a forestry pathologist in Western Australia where more than 40% of native plant species have been affected by the inadvertent introduction of P. cinnamomi (known there as Jarrah dieback). She also described current projects in the global biodiversity hotspot of the Greater Cape Floristic Region of South Africa where many endemic and endangered species are significantly challenged by the spread of P. Cinnamoni. This disease was first reported in South Africa in 1931 from avocado orchards.

Silent spread of phytophthoras occurs via pathways such as human activity, trade in infected nursery plants, agricultural run-off, restoration projects, and by natural dispersal through soil and water movement including during flooding and extreme weather events.

Co-ordinated efforts across sectors were recommended to prevent or reduce threats. Risk assessments to identify vulnerable areas, biosecurity measures including quarantine regulations, monitoring to ensure early detection, hygiene practices, diagnostic tools, and public awareness were identified as key in reducing impacts of these harmful organisms.

Invasive phytophthoras are amongst the top eight biosecurity threats to the New Zealand kiwifruit industry. PFR, KVH, and Zespri have previously worked together on a survey of phytophthora pathogens in kiwifruit orchards throughout the country, to gain an understanding of our current baseline of phytophthora species associated with kiwifruit. A literature review on the potential impacts on kiwifruit and kiwiberry has also been completed.

Biosecurity controls are in place to reduce the risk of phytophthoras being spread through the movement of kiwifruit plants and shelter plants, via the industry Kiwifruit Plant Certification Scheme (KPCS) which identifies phytophthora as a target organism. The Plant Pass scheme for nurseries producing shelter plants only also includes a phytophthora specific module. These schemes ensure traceability, nursery hygiene measures and disease management plans are in place and audited annually.