Studies On Epidemiology Of Grape Bitter-rot And Evaluation Of Fungicides

The grape ripe-rot (Colletotrichum gloeosporioides) is an important factor on grape and occurred more and more seriously year by year.The grape industry suffered losses annually, the quantity and quality of grape were influenced.In order to control grape ripe-rot effectively, the investigation on grape ripe-rot was carried out. Samples which were from Shandong province, Hebei provence and Beijing surburbs were collected and isolated. The symptoms were observed.The overwintering forms, primary infection of grape ripe-rot and relation of infecting and the meteorological factors of temperature, humidity and rainfall on grape ripe-rot were researched in the test, in the laboratory. Effective fungicides were also evaluated to control grape ripe-rot by field trials. The results laid basic supports to control the disease. Primary results were as follows:1. The 2300 grape ripe-rot samples, which were collected from Yantai,Changli,Changping were isolated. Specific microorganisms had been isolated from the rot berry, reproduced in laboratory, introduced into healthy berry and reisolated from the experimentally infected berry, according to Koch's postulates. The common one has been used in following trials.2. C. gloeosporioides overwinter mainly as mycelium in cane, tendril, petiole, penduncle and peduncle in barks. They form acervuli and give a lot of spores in later spring and early summer when raining. Tendril and cane can produce more spores. The more spores on tendril and peduncle and lateral the heavier grape ripe-rot occurred in field.3. The Correlation Analysis of grape ripe-rot with accumulated temperature and rainfall has been analysed. Accumulated temperature and rainfall was the key factors(P<0.01); accumulated temperature and rainfall influenced the net increase of diseased fruits (P<0.05).One of main factors was humidity, and it is closely related with the quantity of spores and the severity of ripe rot in field. Average daily humidity is consistent with the number of spores in field, and when relative humidity is 82.16 % or over 82.16 % the number of conidia could reach the peak after about 4 to 5 days. The impact of temperature on conidia is less important.4. Grape fruit could be infected throughout the growing period, especially during August 6 and August 21 in 2009. Because Cabernet began to ripe at August 6, the fruit was seriously infected. After August 21, due to a larger temperature difference between day and night, lower average temperatures, and smaller rainfall, the incidence of grape ripe-rot droped.Through synthetical analysis, C.gloeosporioides infected seriously from July to August.5. Evaluating fungicides against C. gloeosporioides had been taken out in lab.The results indicated that pyraclostrobin, thiram and thiophanatemethyl had high activity, and it also showed that 1:10 mixtures of azoxystrobin and thiram(1:10) had strong synergeticeffects to C. gloeosporioides. The field results showed that pyraclostrobin, mixture of azoxystrobin and thiram had good effcet, efficacy could reach 87.62%, 49.15% and 41.62%.Through the above experiments, that pyraclostrobin and thiram had high activity was found, which could be served as application in the field.