Cultivation And Application Of Entomopathogenic Nematodes And Study On The Effects Of Abiotic Factors On It

Nowdays,the use of chemical pesticides and a series of fungicides has caused a series of environmental problems,such as pesticide residues,water pollution and heavy metal pollution,which have brought great impact on human society and health.Entomopathogenic nematodes are widely used as a biological pesticide with great potential because of their wide insecticidal ability,strong infectivity,ability to find hosts independently,and safety in use,which has become the second largest inspection-free product.However,due to the limitation of many factors in the large-scale propagation and application of nematodes of insect pathogens,China is still in the initial stage.Therefore,this study took entomopathogenic nematodes as the object,studied the nutritional formula of large-scale cultivation under broad-spectrum raw materials,explored the impact of natural abiotic factors on the survival and reproduction of entomopathogenic nematodes during the application process,and the biological control typical applications provide a scientific basis for the wide application of entomopathogenic nematodes.1?Cultivation of entomopathogenic nematodes.Entomogenous nematodes need abundant proteins for growth and reproduction.In this paper,low-cost carbon sources such as bread worms,soybeans,peanuts,etc.,raw meal,glutinous rice flour,and corn meal,which are widely available,were selected as basic nutrients.The cultivating effects of entomopathogenic nematodes under their respective and different ratios were explored.The results showed that:20%?m/v?breadworm and 4%?m/v?corn flour were used as the basic medium,after one cultivation cycle of entomopathogenic nematodes,the reproduction volume of nematodes reached 26 million pieces/bottle,which lays a foundation for expanding cultivation;Among non-biological impact factors,the addition of 2%?m/v?activated carbon and 3%?m/v?Fe₃O₄ could effectively improve the reproduction environment of entomopathogenic nematodes and increase their reproduction rate.After one cultivation cycle,it could increase by 1-2 million.2?Effects of abiotic factors on the survival of entomopathogenic nematodes.Entomogenous nematodes,as a microbial biological control agent,can be released on plants together with a variety of microelement components currently on the market.This study explored the effects of nano antioxidants widely used on plants and the application of heavy metal ions to entomopathogenic nematodes in plant living environments.The results showed that the concentration and size of nano materials had a greater impact on the survival of insect pathogen nematodes,among which 20±5 nm Fe₃O₄ had the most obvious effect on the survival of entomopathogenic nematodes,with a survival rate as low as 50.00%;Environmental heavy metals also had a greater impact on the survival of entomopathogenic nematodes.The effects of single heavy metals Pb and Cd on insect pathogenic nematodes were more significant than the different heavy metals under composite heavy metals or nano-oxidants.When the concentrations of Pb and Cd were 200 mg/L,their survival rates were 11.11%and 33.33%,respectively.The performance of compound heavy metals on the entomopathogenic nematodes Pb+Cd,Pb+Mn,Pb+Mn+Cd+Ni had a synergistic effect,and its toxicity was stronger.The survival rates are 0,36.67%,0,Mn+Cd,Ni+Cd had an antagonistic effect,the survival rate could reach 60.00%,which may be related to the synergistic and additive effects of metal ions with higher covalent index values.Nanomaterials can adsorb some heavy metals and reduce the toxic and side effects of heavy metals on entomopathogenic nematodes.When nano-Zn O and nano-Ti O2 were added in the above heavy metal environment,the stress of entomopathogenic nematodes was reduced.Under heavy metal stress,the oxidase activity of entomopathogenic nematodes was significantly affected.Whether it is a single heavy metal or a composite heavy metal,the SOD,CAT and POD oxidases of the entomogenous nematode were all shown to be active under the stress of low concentrations of metal ions;As the concentration of metal ions increased,all three appeared to fall first and then rise;when the concentration exceeds the tolerance range of the entomopathogenic nematode,the oxidase activity was destroyed and the lethality increases greatly.3?Application of entomopathogenic nematodes.The application of entomopathogenic nematodes in the control of pests is disturbed by various environmental factors,and its control effect will be greatly reduced.Studies on the control of the big wax borer in the room showed that the big wax borer in direct contact with the entomogenous nematode within 72 hours had a lethal rate of 100%,and its infection effect was directly manifested within 1.5 hours.In the outdoor natural environment,5 mg/L of the above-mentioned nano-Fe₃O₄-treated entomopathogenic nematodes controlled large wax borers,and the mortality rate of large wax borers was as high as 95.00%within 48 hours,which was higher than that of the control group?80.00%?.The 200mg/L nano-Zn O-treated entomopathogenic nematodes control the big borer,and its mortality rate reached 57.33%within 48h.In natural light for 60min,the entomopathogenic nematodes treated with 100mg/L of Zn O,Ti O₂,and Fe₃O₄ controlled the wax moth,and their mortality rates were 48.67%,20.00%,and 23.33%,respectively,within 48 hours.In the field control of rice leaf roller borer,entomopathogenic nematodes with a concentration of 20-100IJ/ml was sprayed in the field.The leaf roller borer began to die after 36h,the mortality rate of the leaf roller borer reached more than50.00%after 48h,and the leaf roller borer The mortality rate reached100%.When investigating the survival of entomogenous nematodes in different parts of rice,the mortality of entomogenous nematodes in three different parts of roots,stems and leaves reached more than 60.00%,and the mortality of entomogenous nematodes in rice stems was the highest.This has certain guiding significance in pest control in the rice field of entomogenous nematodes.