Studies On The Production And Application Of EoNPV Preparations For The Management Of The Tea Looper, Ectropis Obliqua

The tea looper caterpillar,Ectropis obliqua,is one of the major pests of tea bushes in China.Ectropis obliqua nucleopolyhedroviruses(EoNPV) is an effective pathogen of the tea looper larvae and may exert control on the population of this pest. Extensive application of EoNPV preparations in tea gardens is an effective method for the biological control of the tea looper and thereby help to reduce the pesticide residue of tea.In this study,morphology of EoNPV was observed by electron microscopy.The production condition,virulence and application techniques of EoNPV preparations were investigated in the laboratory and field.Using a strategy that combined research,demonstration and extension,the application of EoNPV preparations was widely promoted in tea production.1.Electron microscopy analysis of the occlusion body showed polyhedra containing a single nucleocapsid per envelope of the virion.The size of polyhedra varied from 0.68～3.30μm,with an average of 1.65μm.The size of single-embedded virion averaged 61.05×288.95nm.2.The mass production of EoNPV was achieved by mass rearing of the tea looper larvae with fresh tea leaves and then inoculated the larvae with the virus.The most effective production of the virus was obtained by inoculating 3^rd instar larvae with EoNPV at a concentration of 5×10⁵PIB/ml at 24℃.The yield of EoNPV produced from one larvae could be up to 6.02×10⁸ PIB.The techniques for the production of EoNPV preparations were developed.A virus product(an EoNPV-Bt mixed preparation) has been commercially produced.3.Both an EoNPV preparation and an EoNPV-Bt mixed preparation showed high virulence against E.obliqua.The estimates of LC₅₀ of the two preparations, expressed as the number of times for the dilution of the original preparation,were 1.59×10⁴(EoNPV 1.26×10³ PIB/ml) and 1.37×10⁴(EoNPV0.73×10³ PIB/ml, Bt0.15IU/μl) respectively on the 9^th day after inoculation.4.Field and laboratory evaluations indicated that the applications of the virus preparations could be most effective when targeted at the 1st～2nd instar larvae of the 1^st,2^nd,5^th and 6^th generations in the year.Crown spraying and spotted spraying could reduce the cost of applying EoNPV preparations.The control efficiency of EoNPV-Bt mixed preparation reached more than 81.8%in the field.5.Application of EoNPV preparations against the tea looper was practiced in over 66000 mu tea gardens from 2004 to 2006,and more than 33,000 thousands yuan of economic profit were obtained.The seasonal abundance of E.obliqua was reduced by 77%in the tea gardens in which EoNPV preparations were applied. Meanwhile the population density of spiders and ladybirds was doubled in these tea gardens.Incidences of excessive pesticide residue in tea were not found.Good economic,social and ecological benefits were obtained.