The Study on Root Rot Disease of Rosemary
Date Issued
2007
Date
2007
Author(s)
Wu, Kuei-Wei
DOI
zh-TW
Abstract
Rosemary is one of the economically important fragrant herbs in agricultural industry. In warm and wet summer in Taiwan, however, rosemary is frequently affected with a root rot disease. The disease symptoms include leaf yellowing, wilt, and root browning. Under a microscope, we can find a lot of oospores and chlamydospores in the root tissue. Therefore it was thought to be caused by fungi of the family of Oomycetes. Selective medium developed by Ko et al for isolation of Pythium and Phytophthora was then used to isolate the suspect pathogen from browning roots from about 60 diseased plants. A total of 120 isolates were obtained from these 60 diseased rosemary plants, and among them 98 ％ were Pythium , only 2 ％ were Phytophthora . These 120 isolates were tentatively divided into 20 groups according to their morphology and other characteristics. Results showed that these isolates consisted of 6 species of Pythium and 2 species of Phytophthora . Among them 5 species of Pythium and both Phytophthora were pathogenic to roots of seedlings in test tubes and in pots, or inoculated to healthy pot seedlings. Pythium myriotylum and Phytophthora nicotianae were the dominant species, for these respective genus. The fungicides mancozeb and thiophanate methyl each at 500X concentration were applied by dip every the whole diseased plants for 10, 20 or 60 seconds. Results showed that mancozeb dipping for 20 seconds and thiophanate methyl dipping for 10 seconds are satisfactory for curing the disease. There two fungicides were not phytotoxicity to rosemary. Four root rot pathogens of rosemary including Py. myriotylum, Py. oedochilum, Py. catenulatum, and Ph. nicotianae were also used to inoculate healthy seedlings of cabbage, tomato, and mustard. They all showed root-browning symptom, after the inoculation. In conclusion, the Koch`s postulates of this disease has been proven, and the pathogens were identified. It should benefit the diagnose and control the disease in the future.
Subjects
迷迭香
根腐病
腐霉菌
疫病菌
Rosemary
Root rot
Pythium
Phytophthora
Type
other
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