Control And Filed Incidences Of Cucumber Phytophthora Blight In Hunan Province

Cucumber phytophthora blight is a plant disease caused by Phytophthora melonis Katsura, which is hard to control once it occured. This disease can cause a very serious economic loss,which would be30%-40%yield loss or the whole field crop. In this study, we investigated the Occurrence regularity and influence factors of Cucumber phytophthora blight in Hengyang and Hanshou city of Hunan province. Furthermore, the identification and prevention technology of Phytophthora melonis resistant species were studied in this paper.The main results were as follow:The disease epidemic curve of Phytophthora melonis in Hunan showed a trend of drop after increase. It initially happenedin the mid to late of April to early May of each year, reached the peak at the end of May to early June and then gradually declined. Cucumber phytophthora blight disease were investigated in incidence area of Changde and Hengyang at four times which were seedling stage, flowering period (first female flowers open), early fruiting period (a melon sit up),the heighter fruiting period. The disease heavier in early flowering season,and lighter in seedling stage.To carry out the investigation in Hengyang and Hanshou city of Hunan province, in2012and2013. Hengyang and HanShou fixed-point, regular monitoring fixed-point monitoring on a regular basis. The results showed that:The temperature in the range of19.8-31.9℃is suitable for Cucumber phytophthora blight, A direct proportion relationship with disease onset and density of the heavy rain.Through multiple regression analysis of meteorological factors during the Cucumber growing seasons in the area, establish the region Cucumber phytophthora blight prediction model of Hengyang and hanshou. Forecasting Cucumber phytophthora blight disease index in Hengyang by hengyang model, the prediction accuracy in2012and2013achievid84.32%and84.57%. Forecasting Cucumber phytophthora blight disease index in hanshou by hanshou model, the prediction accuracy in2012and2013achievid80.72%and81.24%.Resistance test of seven cucumber varieties indicated that Jincuichunsi, Kangmishuiguo and tangshanqiugua showed medium resistance while JiWang cucumber was susceptible to this disease. No high resistant variety were found. Control effect on Streptomyces purpeofuscus fermentation liquor, metalaxyl-Mn-Zn, Dimethomorph, the combination of Streptomyces purpeofuscus fermentation liquor and metalaxyl-Mn-Zn four fungicides to Phytophthora melonis was compared. The results showed the control effect of metalaxyl-Mn-Zn was the lowest of60%, while control effect of other three treatments were all to80%, of which the combination of Streptomyces purpeofuscus fermentation liquor and metalaxyl-Mn-Zn got the highest control effect of91.7%.