Disinfectants

We have tested a number of products to determine which disinfectant can be used in the forest, which is not only effective against the pathogen but is also safe to use by the public

and environmentally friendly. Although there are other products available that are likely to be more effective against the pathogen, sterigene was found to have a better all-round profile in terms of having less of an impact on the environment and is safe to use compared to other disinfectants tested.

IMPORTANT: Sterigene will not kill spores if they are embedded in soil, hence the application of sterigene should only occur AFTER ALL soil is removed using a scrubbing brush and water.

Phosphites

Overseas and also in New Zealand, a chemical called phosphite has been successfully used to reduce the impact of other Phytophthora species on tree species. It works by temporarily boosting the tree’s natural defences to help the tree tolerate the disease and hence reduce its impact. Our research have found that phosphite by trunk injection showed the most potential in reducing the impact of the disease.

A five-year field trial was completed in 2017 and showed that phosphite injections appeared to have successfully healed trunk lesions of infected kauri juvenile trees. However a number of uncertainties remain in terms of the longevity of treatment efficacy as well as the frequency of treatment for long-term control. Further research is occurring to address these gaps as well as investigating the use of phosphite injections in larger mature trees and the use of phosphite sprays on trunk lesions.

Genetic tolerance or resistance

Unfortunately most trees that are infected with the disease will eventually die, regardless of their size and age, however scientists believe that it is possible that a small population of kauri may show and increase tolerance or resistance to the disease and its impacts.

The Programme hopes to find kauri that show or develop natural resistance towards the disease. The Healthy Trees, Healthy Future Programme, which is run by Scion and co-funded by the programme, seeks to find genetically resistant trees and to breed and hopefully one day plant disease-resistant kauri in infected areas to restore these areas to their former glory.

For future information on the Healthy Trees, Healthy Future Programme and the progress being made, please refer to https://healthytrees.co.nz/

Biological control and alternative treatments

We are exploring other control options, including biological control and other alternative treatments. Research in this space is ongoing.

The programme receives a number of enquiries from concerned members of the public recommending certain products to test against the pathogen. As a result, we subsequently screen these products, with the most promising being selected for further testing. The programme values the public’s opinion so please send any of your ideas or suggestions to kauridieback@mpi.govt.nz.

Oospore Deactivation

The lifecycle of the pathogen consists of a number of life states or stages. We have found that killing the resting spore or ‘Oospore’ of the pathogen is the most difficult to achieve given it has a think cell wall which protects it from the environment. Our aim is to find control tools which will deactivate or kill the Oospore. Current research involves the use of temperature and p.H.