Study of non-pesticide control on foot rot disease of sweet potato

• Main Authors: Hsueh-Hung Chen, 陳學弘
• Other Authors: 孫岩章
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/f6ypqp

碩士 === 國立臺灣大學 === 植物醫學碩士學位學程 === 105 === Foot rot disease, caused by Phomopsis destruens, is the most important disease of sweet potato in Taiwan. The symptoms include stem rot, leaf yellowing, plant wilt and storage tuber rot. In 2016, two fungicides are officially recommended for controlling this disease. However, due to the growing concern about food safety, pesticide residues and environment sustainability in recent years, reducing the use of synthetic pesticides has become a general trend. Therefore, the aim of this study is to investigate the cultivation type and incidence of foot rot disease in northern Taiwan, and to screen some non-pesticides with potential to control foot rot disease of sweet potato. According to official data, it was a year of bumper harvest for sweet potato in Jinshan and Wanli area in 2016. While the loss of yield caused by foot rot disease was minor in that year. Due to the outbreak of an extremely cold front happened in January in 2016, this study tried to elucidate whether low-temperature could affect the survival of pathogens. The results showed that after treating diseased tissues with 4℃ low temperature for 5 days, isolation rate of the pathogen had reduced to 20%, but could be isolated after 14 days. The conidia germination rate of P. destruens was about 43% after low-temperature treatment for 14 days. Thus, it was assumed that low temperature has important influence on the survival of pathogen. The cinnamon leaf oil (CLO) and the potassium salt of coconut oil (COPS), selected from 23 essential oils and 5 potassium salts of fatty acid (FAPS), were found to have an additive inhibition effect on P. destruens after mixed with a specific ratio, which was used therefore in this study. In the pot assay, results indicated that CLO + COPS can achieve better control effect as compared with control or that applied alone. The fungicides including thiabendazole, difenoconazole, propiconazole, hexaconazole and carbendazim + hexaconazole also showed good control efficacy for foot rot disease. However, the treated antagonistic microorganisms did not show controlling efficacy for foot rot disease. In the dipping therapy assay for diseased seedlings, results revealed that both thiabendazole and CLO + COPS treatments can reduce the disease severity after 40 and 60 days cultivation. In the dipping control assay of sweet potato storage tubers, CLO + COPS, thiabendazole, difenoconazole, propiconazole, and carbendazim + hexaconazole showed significantly decrease of severity of foot rot disease. In conclusion, CLO + COPS does have potential to control foot rot disease. The relationship between climate factors and incidence of foot rot disease should be observed continuously in the future. In order to achieve better control efficacy, the timing and frequency of treatment including non-pesticides and pesticides should also be further studied.