Forest efficacy trials on phosphite for control of kauri dieback


  • I.J. Horner
  • E.G. Hough
  • M.B. Horner



In 2012 trials were established in four kauri forest sites severely affected by kauri dieback (Phytophthora agathidicida P taxon Agathis PTA) to determine the potential of phosphorous acid (phosphite) as a control tool Baseline assessments of 162 trial trees included canopy disease rating trunk lesion dimensions and lesion activity (recent bleeding/ 20cm intervals around the trunk Control trees were left untreated After 1 year half the previously injected trees were reinjected in all cases with 75 phosphite Phytotoxicity symptoms (leaf yellowing browning or leaf/twig abscission) were noted in some phosphiteinjected trees particularly where the 20 concentration was used After 3 years many more trunk lesions remained active (expressing ooze continued expansion) in untreated trees (585) than in phosphitetreated trees (08) Average lesion expansion after 3 years was 127 cm in untreated and 04 cm in phosphitetreated trees




How to Cite

Horner, I., Hough, E. and Horner, M. 2015. Forest efficacy trials on phosphite for control of kauri dieback. New Zealand Plant Protection. 68, (Jan. 2015), 7–12. DOI:




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