Journal of Taiwan Agricultural Research

Author:Lih-Ling Chern, Pao-Jen Ann*, Jiunn-Feng Su, Cheng-Wei Yang, Hsing-Chun Tsay, Jyh-Nong Tsai, and Ting-Fang Hsieh

Abstract:

      Malabar chestnut (Pachira macrocarpa Schl. et L. H. Bailey) seedlings are important potted ornamental plants for export in Taiwan. The main production area in Taiwan is at Sijhou, Changhua County. In recent years, production of Malabar chestnut has been impacted with diseases that caused root and basal rots of seedlings, leading to the death of seedlings in the field, loss of braids, and rots of plants in storage container during shipping. Our previous studies indicated that Phytophthora palmivora and Phytophthora nicotianae (= P. parasitica) were two of the major causal organisms that caused the problem. These Phytophthora spp. were able to infect entire Malabar chestnut plant at any production stages, including transplants, braiding, or growth in the field. The main objective of this study was to screen chemicals for Phytophthora disease control in Malabar chestnut seedlings. A total of 18 recommended chemicals for Phytophthora diseases of other crops were tested for their effectiveness in vitro in inhibition of sporangial germination and mycelial growth of P. palmivora isolated from the host. Those demonstrated high inhibitions were selected for green house tests. Results showed that several tested chemicals were very effective in reducing seedling blight of Malabar chestnut seedlings, including (listed in descending order of effectiveness) neutralized phosphorous acid (1,000× dilution), 4-4 Bordeaux mixture, 25% mandipropamid (2,500× dilution), 80% mancozeb (500× dilution), 50% dimethomorph (3,000× dilution), and 58% mancozeb + metalaxyl (1,000× dilution).

Key words:Phytophthora diseases, Malabar chestnut, Phytophthora palmivora, Chemical control

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