Effect Of Isaria Javanicainfection On Tomato Yellow Leaf Curl Virus In Bemisia Tabaci

Bemisia tabaci(Gennadius)is one of the most important pests in the world,and it is complex and changeable,there are a variety of secondary symbiotic bacteria which are beneficial to the reproduction and stress resistance of the insect pest,so it is hard to control the pest.As the only vector of tomato yellow leaf curl virus(TYLCV),the occurrence of B.tabaci is usually accompanied by the outbreak of tomato virus diseases,TYLCV has become the main leaf diseases affecting tomato yield and quality.At present,chemical control is still an important means to control the whitefly,B.tabaci,whereas because of wax powder in the body of whitefly,and its resistance to most of the pesticides,the traditional way of chemical control now is unable to meet the urgent needs of the prevention and control of whitefly,and biological control are becoming increasingly important because of its obvious advantages.Isaria javanicais an important entomopathogenic fungus infected B.tabaci,under suitable conditions,it can be epidemic in the whitefly population,which resulted in effective prevention and control of whitefly.In this study,an isolate of I.javanica have been isolated previously,based on this,the effects of I.javanicainfectionon the accumulation and transmission capability of whitefly were studied.The results is beneficial to further understand the interaction of pathogen fungi and plant virus in the insect vector,and the biological characteristics of Bemisia tabaciwhich will enhance the level of biological control.The main results are as follows:(1)Effect of I.javanicainfection on TYLCV content in B.tabaci:This study showed that after I.javanica treatment,TYLCV content in the whitefly decreased.The decreasing rate varied with the developing stages of the whitefly and the concentration of the fungus.The content of TYLCV decreased with the increase of fungi concentration.When the adults treated with a higher concentration(2×106 spores/ml),the content of the virus in the vector decreased more than that when the nymphs treated with the same concentration.The experimental results showed that I.javanicainfection virus suppressed the accumulation of TYLCV in the whitefly.(2)Effect of I.javanicainfection on TYLCV transmission of B.tabaci:Both adults and nymphs of B.tabaciwere treated with two concentrations of 1.javanica.The results showed that,either the treated adults or the treated nymphs of B.tabaciwere used to inoculate TYLCV into healthy tomato plants,the plant heightand disease index of tomato all were positively affected by the fungus infection,which showed that the transmission capacities of TYLCV significantly decreased by I.javanicainfection.The findings indicated that I.javanica infectionis were not only important in the control of the vector,but also important in suppressing the transmission of the plant virus,which would be an ideal insecticide in controlling the vector of plant virus.