Phytophthora is a genus of fungus-like plant pathogens that pose a major challenge to global biosecurity, with over 130 soil or air borne species known to cause serious diseases across forestry, horticulture, agriculture and natural ecosystems.

“Phytophthora pathogens are microscopic and very easily spread,” says Dr Teulon, Director of Better Border Biosecurity. “They affect an increasingly broad range of hosts worldwide that, with the rapid movement of organic material between countries, has escalated the abundance of diseases they cause. Once established, they are virtually impossible to eradicate or contain, and very difficult and costly to manage.”

Dr Teulon says there is a range of research projects underway within the B3 collaboration aimed at protecting New Zealand from these unwanted pathogens.

Plant pathologist at Scion, Dr Peter Scott, says the research is complicated by some species of Phytophthora producing hybrid pathogens, which are known to be the cause of serious plant diseases.

“Others species are rapidly evolving in response to new environments and hosts, and are developing resistance to different chemical controls,” says Dr Scott. “We are conducting a review of global Phytophthora diseases to determine the risk of different pathogen species and their possible entry pathways to New Zealand. We are comparing the diversity of native and introduced host species using a range of techniques, and identifying the risks of a range of known and unknown Phytophthora pathogens”.

Dr Scott says these data will be used to map the movement of the pathogens between countries and the likely risks they pose to indigenous and introduced flora should they arrive in New Zealand. He adds that one of the biggest questions when dealing with a new forest disease is determining whether the causal organism is new to New Zealand or has undergone a behavioural change, or hybridised.

Researchers can assess the genome of the pathogen to determine its genetic diversity, which may indicate how long it has been in New Zealand. This is currently being done for Phytophthora pluvialis, the known cause of red needle cast disease. Dr Scott says it is also important to determine the how these pathogens are being introduced into the country to prevent further unwanted organisms from entering.

Phosphite is one of the only chemical treatments known to effectively and economically control large scale Phytophthora disease, and in the event of an incursion may be applied aerially to help contain the infection and reduce the rate of spread. However, at an effective rate of application, phosphite may have some undesirable visible and non-visible symptoms in plants, including burning and impacts on fertility.

In preparation for a rapid response to a possible Phytophthora incursion, B3 researchers have established the phytotoxic sensitivity of 13 keystone native New Zealand species and two important forestry species by quantifying foliar burn and non-visual physiological symptoms.

In addition to the New Zealand national collaborations, Phytophthora research has been selected by B3 to be a focus of the NZ-US Joint Commission on Science and Technology Collaboration Invasive Species Priority Topic, to develop research synergies between New Zealand and the United States on this global issue.

Dr Rebecca Ganley, Research Leader, Scion.

DDI: 03 343 5767