The aim of the research was to investigate if it is viable to use natural plant hormones to induce a defence response in the Kauri tree that might inhibit or stop infection via Phytophthora. Results showed that treatment with the hormone methyl jasmonate increased natural defensive phenolic compounds and lignin within the Kauri leaves. These phenolic compounds in turn were shown to inhibit but not stop the growth of Phytophthora cinnamomi. This was demonstrated in vivo and in vitro using detached leaf assays and inhibition of growth on V8 agar. Conversely treatment with the plant hormone salicylic acid was less effective at inducing phenolic production. In conclusion it was found that plant hormone treatment alone was not enough to prevent Phytophthora cinnamomi from infecting Kauri. Although hormone treatment did increase phenolic production, this alone was not enough to eliminate the pathogen. In future it may be possible to combine plant hormone treatment with other methods to produce an effective means to eliminate or prevent further distribution of Phytophthora.