Screening And Evalutation Of Entomopahogenic Nematodes And Development Of Formulation

Entomopathogenic nematodes(EPNs) are a group of nematodes(thread worms), causing death to insects. EPNs occur naturally in soil environments and locate their host in response to carbon dioxide, vibration and other chemical cues. Entomopathogenic nematodes live parasitically inside the infected insect host, and so they are termed as endoparasitic. They infect many different types of insects living in the soil. EPNs fit nicely into integrated pest management or IPM programs because they are considered non-toxic to humans, relatively specific to their target pest(s), and can be applied with standard pesticide equipment. Many species EPNs have been effectively used as biological insecticides to control underground pests. In order to screen broad spectrum and high pathogenicity EPNs, we compared the pathogenicity of 12 kinds or strains of EPNs against some insect pests by bioassay. meanwhile, the stress tolerance and control effciency in field of these EPNs were compared to find commercial development potential EPNs. Formulation of entomopathogenic nematodes also was developed in order to prolong the shelf-life of EPNs. The results are as follows.1. The pathogenicities of 12 kinds of EPNs against Agrotis ypsilon larvae, Agrotis segetum larvae, Athetis lepigone larvae and Atrijuglans hetaohei larvae were measured by bioassay. The results indicated that The pathogenicities of Steinernema glaseri Sgib and Heterorhabditis bacteriophora HB8 to four species of pests were highest. The pathogenicities of Sgib and HB8 against A. hetaohei larvae was determined by sand-burying methord. The pathogenicity of Sgib was higher than HB8.Furthermore, The the heat tolerances and dry tolerances of 10 kinds of EPNs were determined. The results showed that the stress tolerances of Sgib was strongest. In the field trials, Sgib indicated good control effect with 96.67% mortality of A. segetum larvae.2. The influence of temperature,soil moisture and dosage on virulence of Sgib to A. segetum was tested under laboratory condition. The results showed that virulence of Sgib to A. segetum larvae was the optimum at 21℃-27℃, 20% soil moisture and 10:1 ratio of nematode to insect. In the field trials, Sgib indicated good control effect with 96.67% of A. segetum mortality.3. Determination of entomopathogenic nematodes to the temperature and the humidity sensitivity, the results show that Sgib by 35 ℃ 3 h after treatment survival rate for 89.38% and 40 ℃ for one hour survival rate of 50.4%; the humidity for 50.5% of the small room humidity is measured after 5h survival rate for 76.05% higher than that of other nematode strains.3. The powder formulation of Sgib was determined through screening of matrix, water, retaining water agent and preservatives: 30% white carbon black, 69.4% water, 0.5% sodium carboxymethyl cellulose and 0.1% methyl aldehyde. When Sgib powder agent of one million Sgib IJs per gram substrate was kept at 10℃, survival rate powder of Sgib at 30 day was 100%, survival rate at 60 d was 92.38%.