Studies On The Pathology Of EpNPV And The Specialty Of EpNPV-Bt Preparation

Euproctis pseudoconspersa Strand, a nationwide important pest in tea garden, often causes huge economic loss, and the chemical pesticides easily brings on the problems such as pesticide residue and resistance. Euproctis pseudoconspersa Strand nuclear polyhedrosis virus (EpNPV), a highly infectious and selective pathogen of Euproctis pseudoconspersa Strand which is an effective control measure by bringing polyhedrosis in tea garden. Bacillus thuringiensis (Bt) , a widely used broad-spectrum insecticide has good control effects against many kinds of pests in tea garden. EpNPV-Bt preparation, a new biological pesticide which is a mixture of bacillus thuringiensis and Euproctis pseudoconspersa Strand nuclear polyhedrosis virus, is provided with the virtue of non-toxicity, non-residue and non-pollution. Utilizing such techniques as embed, super-thin slice, transmission and scanning electron microscope to conduct the studies on the morphology and pathology of EpNPV;bioassay were conducted to study the virulence, field efficiency, associated toxicity and specialty of EpNPV-Bt. The research results are as follows:1. EpNPV is a kind of nuclear polyhedrosis virus. The polyhedra of EpNPV are an anomalous polyhedron, in which two types of virions were embedded: single embedded virus and multiple embedded virus. The multiple embedded virus has two virions in eachbundle. The size of phlyhedra varied from 0. 95~2. 69μm, averaged 1.72 ± 0.07μm. The size of multiple embedded virus averaged 280. 72 + 4. 13nm×52.71 ± 1.09nm, the size of single embedded virus averaged 271. 08 + 4. 70nm×63.25 + 0.93nm.2. The virions infected the midgut cells, the number of polyhedra increased accompanied with the increased infection time. At first, the viroplasm were observed in nuclei and the new nucleocapsids without envelope were replicated in the viroplasm. Afterwards, polyhedral protein accumulated around enveloped mucleocapsids. Later on, the mature polyhedra appeared in nuclei, The cell showed grievous pathological changes. The pathological changes are consistent with the symptom of the larvae.3. Under different time and temperature, the associated toxicity index of EpNPV-Bt is dynamic. The EpNPV-Bt mostly possesses joint action. Fromforegoing of the 16 'C , 19 "C and 28 °C treatment, the EpNPV-Bt showed synergism.4. The EpNPV-Bt showed such specialty as anti-feeding effect and immediate functioning against the larvae of Euproctis pseudoconspersa Strand. Under 28°C, for killing 30 percent of larvae (LT3o), EpNPV-Bt costed 3. 8d less than EpNPV, with the efficiency nearly doubled. The antifeedant efficiency of EpNPV-Bt on the 19th day was 66.2% against the larvae of Euproctis pseudoconspersa Strand.5. The LCso of EpNPV-Bt is 9769 + 1065X (EpNPV2X 103PIB/ml, Bt 0.2IU/ yl) . The field efficiency of EpNPV-Bt (1000 X) reaches 96.8% on the 18th day.6. The EpNPV-Bt showed a good effect of controlling against the larvae of Iragoides fasciata Moore and Junkowskia athleta Oberthur, bringing 85. 8 and 65.6 percent of them to death within 7 days.