Fungitoxicity of systemic fungicides and their control efficacy against Phytophthora root and foot rot of Tangerine
1992
Thanit Plongbunchong
Efficacy of potential and selected fungicides e.g. (m-dKP, dimethomorph, metalaxyl, fosethyl-Al, and captan) was evaluated against root and foot rot of tangerine. The m-dKP and dimethomorph proved to be the best fungicides as well as metalaxyl and fosetyl-Al, interm of in vitro and in vivo trials when tested against Phytophthora parasitica. Laboratory study revealed that ED50 values of m-dKP and dimethomorph against Phytophthora spp. were less than 52.5 and 1.0 mg/L, respectively. But dimethomorph could not be toxic to Pythium spp. (ED501,000.0 mg/L). Pertaining to toxic of m-dKP against in vitro growth of selected higher fungal pathogen, the minimun ED50 values (300 mg/L) obtained when tested against Helminthosporium turcicum, Phomopsis sp, Botryodiplodia theobromae and Melanconium fuligineum. Evaluation on efficacy of m-dKP against root rot of tangerine stocks in greenhouse was conducted via soil drench and foliar spray. After 45 days from first treatment the diseased stocks still survived and recovered from infection, whereas the non treated stocks were dead. Besides, field trial on controlling root rot was conducted via injection, soil drenching and foliar spray. Tangerine trees could be injected with m-dKP and gave satisfactorily control (3 month-interval with 32 g.a.i/tree/year). Regarding foliar spray and soil drenching, metalaxy, m-dKP, dimethomorhp and fosetyl-Al provided the best control and recovery for at least 3-6 months.
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