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Phytophthora Diseases of Avocado in Taiwan
Symptoms of avocado plants attacked by phyophthora. Diseased plants showing slow decline and twig dieback (Fig.1) or quick decline (Fig.2), diseased roots (Fig.3), An infected fruit (Fig.4)
Symptoms of avocado plants attacked by phyophthora. Diseased plants showing slow decline and twig dieback (Fig.1) or quick decline (Fig.2), diseased roots (Fig.3), An infected fruit (Fig.4)

Author:Pao-Jen Ann*, In-Ting Wang, Fu-Hsin Chang, Jyh-Nong Tsai and Hsin-Der Shih

Abstract:

    Decline and death of avocado trees are very common in Taiwan in recent years. Diseased plants showed symptoms of stem dieback, leaf yellowing and defoliation, and serious root rot and necrosis. All infected trees died eventually 3-5 years after appearance of declining symptoms. Avocado trees also showed quick decline symptoms. The whole trees wilted and died within 1-2 months after flooding as a result of serious Typhoon. A total of 14 diseased avocado orchards were surveyed from 1977 to 2004. Phytophthora was detected from diseased tissues of all tested orchards and two species, P. cinnamomi and P. palmivora, were obtained. P. cinnamomi (7A1 and 57A2 isolates) was isolated from 11 orchards, and P. palmivora (24 A2 isolates) was obtained from 3 orchards. An A2 isolate of P. palmivora was also obtained from a diseased fruit. Both Phytophthora species were of the typical type based on Waterhouse's Description. Tested isolates of P. cinnamomi and P. palmivora were shown to be pathogenic to avocado seedling roots and fruit, respectively, and the same fungi were reisolated from inoculated diseased tissues. Phosphorous acid, Fosetyl-aluminum and Metalaxyl mancozeb were effective in decreasing Phytophthora root rot of avocado seedlings in pot study.

Key words:Avocado, Root rot, Phytophthora cinnamomi, P. palmivora

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Journal of
Taiwan Agricultural Research
Vol. 73, No.1 (2024) ISSN: 2790-086X Vol. 73, No.1 (2024)
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