Primary Study On Key Factors Influencing The Epidemic Of Cucumber Powdery Mildew And Disease Control

Four experimental fields were chosen in the trial field of Agricultural University of Hebei and in the suburb of Baoding city. The epidemic of cucumber powdery mildew on three varietious (Changchunmici, Jinyan-2 and Jinyan-4) was studied in field condition. The weather data in field were recorded hourly by hygrothermograph and rain game. From the start of disease in field, the number of newly disease leaves was accounted everyday on investigation plants and the days with large number of disease occurrence were figured out. Inoculations were made every 4 days on healthy leaves far from diseased area, and the latent periods were measure during the whole growing season.The days with heavy infection were detected by mouing the days with large number of disease occurrence one latent period forward. The crucial weather conations for heavy infection of cucumber powdery mildew were summarized as follows: one hour of rainfall in the critical factor, followed by 24 hours with air relative humidity higher than 47%and temperature between 18 and 28.5 .Bioassay on mixtures of different proportions between diniconazole and plant extract Ts-109 was carried out on cucumber seedlings outside and inside greenhouse. Result showed that the proportions of 2: 1 and 3: 1 is better than the other. The mixtures of 2:1(600 dilution) and 3:1(1200 dilution), protective efficacies, which were at the same remarkable, level with the standard chemical 12.5% diniconazole WP (3000 dilution). Two mixtures only contained diniconazole 5.6% and 5.0% compared to original standard chemical use.Both mixtures showed protective efficacies, which is over 73% as good as 12.5% diniconazole WP(3000 dilution) under field conditions. The two mixtures reduced the amount of chemical diniconazole up to 90.0% of the original standard dosage.Physiological studies showed that Ts-109 extract could increase the account of chlorophyll of cucumber seedlings and made plant grow stronger, and more resistant to plant disease.After being fretted by Ts-109 extract and diniconazole, the activities oft some oxidize enzymes, such as SOD, POD and PPO. The MDA contents and relative were also influenced. POD and PPO were strengthened and MDA and relative conductance rate reduced. Ts-109 and diniconazole showed the same trend.