Abstract:

In order to improve the precise prevention and control level for downy mildew in facility-grown cucumber in spring in Wuhan, this study constructed a disease-promoting meteorological index and suitability grading standards based on meteorological observation data of Wuhan from 1951 to 2021 and disease monitoring data from 2011 to 2021, with identified temperature and humidity as core driving factors. Furthermore, the index accuracy was evaluated and climate risk characteristics of disease occurrence and epidemic were analyzed. The results show that: (1) the disease-promoting meteorological index has an accuracy of 100% in assessing the intensity of the disease, and an accuracy of 75% in predicting the initial day of the epidemic, which can objectively reflect the time and extent of the disease. (2) From 1951 to 2021, the outbreak years of downy mildew and the number of suitable and above epidemic days (DESA) showed a trend of "stable in the first 40 years, and first decreased and then increased in the last 31 years". The outbreak years from 2011 to 2021 doubled compared with 2001-2010, and the growth rate of DESA days from 2006 to 2021 reached 17.2 d/10a, the epidemic risk and intensity of the disease were significantly enhanced. (3) The suitable prevalence period of cucumber downy mildew in Wuhan begins on average on March 19th. It enters the medium-high risk period of downy mildew prevalence in mid-March, the high-risk period after late March, and the highest risk period is from early April to late April. Moreover the disease has a significant trend of early onset in the past 31 years (the proportion of early-onset years increased by 2.4 times). (4) The beginning of the suitable epidemic period of the disease in the facility environment is 1 month earlier than in the open field. The disease-promoting meteorological index constructed in this study can provide a scientific tool for monitoring and early warning of cucumber downy mildew. It is recommended that the plant protection department initiate special monitoring in early March and promptly regulate the temperature and humidity of facilities.

Key words: cucumber downy mildew, disease-promoting meteorological index, pathogenesis regularity, risk characteristic, meteorological factors, monitoring and early warning, prevention