New Zealand Plant Protection 68 (2015): 7-12
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/ 20-cm intervals around the trunk. Control trees were left untreated. After 1 year, half the previously injected trees were re-injected, in all cases with 7.5% 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 (58.5%) than in phosphite-treated trees (0.8%). Average lesion expansion after 3 years was 12.7 cm in untreated and 0.4 cm in phosphite-treated trees.
Keywords: Phytophthora agathidicida, PTA, kauri, Agathis australis, control.
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N.W. Waipara, S. Hill, L.M.W. Hill, E.G. Hough and I.J. Horner (2013)
New Zealand Plant Protection 66: 235-241
|Phosphorous acid for controlling Phytophthora taxon Agathis in kauri: glasshouse trials|
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Copyright © 2015 New Zealand Plant Protection Society (Inc.).