Occurrence And Prevention, Cure Of Black-Dot Disease On Bagged Apple Of Fruits Producing Area In Shaanxi Province

The research was carried out between 2005 and 2006 in the apple producing area in Shaanxi province, choosing Red Fuji and Gala as the samples to aim at finding out the relationship between the occuring rate of the black-dotted disease and the orchards in varied altitudes, different types of apples, the brands of fruit bags used and the varied management levels, moreover spraying germicide before and after bagged , with the purpose to finding the principle ruling the occurrence of the disease, so as to offer supporting information in theory for the cure of it. The experimental data indicate the followings:1. In Shaanxi province, the black-dotted disease in the bagged red Fuji apples begin in the early part of July, reached its peak in late July and early August. After that the disease condition becomes stable till being picked-up. The climax of the disease coincides with a period hotter and more humid, as a result, the occurrence and the development of the disease is closely related to the temperature and the humidity of the areas.2. The occurrence of the disease varies from elevation, apple varieties and the different parts of the fruit trees, the disease in area at high elevation was serious than that at lower elevation. The occuring rate of the black-dotted disease of red Fuji was serious than Gala. In the middle, bottom and inside crown of the apple trees, the disease was serious than that at the top and outside.3. In terms of fruit bag used, that also attribute to the occurrence of the disease. the disease occurrence rate in apples treated with Xiaolin, Jinggong and Sanqin bags was lower in Luochuan and Yangling, while that with Jinggong, Sanqing and Seigo ones lower in Baishui.4. Getting rid of calyx decreased the occurrence rate in Yangling and Luochuan. It show that the body of calyx is the bed of germ of the black-dotted disease. Enlarging and closing the vent of bags substantially decreased the rate.5. Spraying a 8000 times Lazole is more effective on the afternoon before putting bages on the fruits than other insecticides. The combination of the 1500 times Yibao, 8000 times Lazole , and 800 times Penke is more effective in fighting against the black-dotted disease in the stage of fruits bagged.6. The changing tendency of the activity of defendant enzyme in the graded disease fruits are the same, all fellows the principle: higher at the beginning and lower later. The climax of the activity of POD and SOD all emerge in the diseased fruit of the first grade while the climax of the activity of CAT, PPO and PAL all can be found in the diseased fruits of the second class. From which we may know that in terms of the fighting against the invasion of the black-dotted disease germs, SOD and POD are relatively faster than the other 3 defendant enzyme.The 2 enzyme play important roles in the preliminary stage of the disease. Meanwhile the activities of other 3 defendant enzyme, especially SOD and CAT, are higher in the diseased fruits of the 2nd, 3rd and 4th levels. It is 2 to 6 times that of the not diseased fruits in terms of ferment activities. Above-mentioned results indicate that in the period when the condition of the disease worsened, the 2 defendant enzyme play relatively important roles to cure the Black-dot disease.