Study On Occurrence、Pathogens Variation And Control Of Watermelon And Melon Gummy Stem Blight In Suburbs Of Nanning

Gummy stem blight was one of the important factors that limited high yield and quality of watermelon and melon. The situation of gummy stem blight of watermelon and melon in suburbs of Nanning, Guangxi Zhuang Autonomous Reqion was surveyed and analysed in this study. Samples of gummy stem blight of watermelon and melon were collected from different cities such as Nanning, Beihai, Guilin and Liuzhou, pathogen was isolated、pathogenicity of pathgen was tested and diseases control was made. The preliminary results would provide basic data for understanding the occurrence and pathogens variation of gummy stem blight of watermelon and melon, screening high effective and low toxic fungicides and effective biocontrol isolates or controlling the disease in order to promoting the sustainable development of the watermelon and melon industry. The following results had been achieved:1. The occurrence and features of gummy stem blight of watermelon and melon in Nanning suburb which were observed at a fixed site and result were as follows:the incidence of gummy stem blight was higher in hot and humid environment. Generally the disease appeared in April at the beginning and the most serious injury stage was in mid-May to June and late September to November. In the most serious injury stage the disease incidence was as high as100%in some field and the death rate was above35%. The disease happened sporadically when the weather was dry, disease incidence was between3%to10%. The disease developed rapidly when it had heavy rainfall and high relative humidity of air. The disease weakly influenced to seedlings and the incidence was low on seedling stage. The disease often occurred heavily when watermelon and melon turned into reproductive period and became a serious disease at the middle-late stage.2. After virulence of different pathogen isolates was tested, it was found that virulence of different isolates to the same watermelon variety was significantly different and virulence of the same pathogen isolate to different watermelon and melon varieties was obviously different. There were differences on physiological and biochemical characters among different isolates. The pathogens collected in Nanning suburb、Beihai、Guilin and Liuzhou were all identified as a type of Didymella bryoniae based on molecular biological technique. After ITS sequences of19pathogen isolates were compared, it was found that there were little difference between different isolates and it meant genetic diversity between isolates was not obvious.3. Inhibition of fungicides such as25%pyraclostrobin EC,43%tebuconazole SC,40%flusilazole EC,25%propiconazole EC,10%difenoconazole SC and45%prochloraz EW and biocontrol agents such as trichoderma virides0031Ⅰ④,0045Ⅰ①,0024Ⅱ to pathogen were tested in lab. and it showed25%pyraclostrobin EC,43%tebuconazole SC,40%flusilazole EC,25%propiconazole EC,10%difenoconazole SC and45%prochloraz EW had significant inhibition to this pathogen and Trichoderma virides0031Ⅰ④,0045I①,0024II had significant inhibition to this pathogen, too. Three fungicides (45%Prochloraz EW,25%Propiconazole EC and10%Difenoconazole SC) and3Trichoderma virides (0031Ⅰ④,0045Ⅰ①,0024Ⅱ) were applied in potted plants of watermelon and melon, the results showed that control efficiencies of45%Prochloraz EW and25%Propiconazole EC were91.19%and87.07%, respectively; the control efficiency of10%Difenoconazole SC was only70.80%; control efficiency of Trichoderma virides0031Ⅰ④was72.07%; and control efficiencies of Trichoderma virides0024Ⅱ and0045Ⅰ①were only59.14%and45.16%.