Preparation And Application Of RNAi Wettable Powder For Lepidopteran Pests Control

China ’s agriculture and forestry have been disturbed by Lepidoptera pests for a long time.In this paper,biological control of Lepidoptera pests was carried out.Microbial pesticides prepared based on the principle of RNA interference were applied to Lepidoptera pests,which could induce pest RNA interference effect and eventually die.In our previous study,we successfully constructed double-stranded RNA engineering bacteria with acetylcholinesterase,a key enzyme in the growth of Helicoverpa armigera,Plutella xylostella and Spodoptera exigua,as the target gene.In this paper,the double-stranded RNA engineering bacteria were induced and cultured,and the bacteria liquid and freeze-dried powder were fed to 2 instar pests respectively.It was found that the freeze-dried powder had better control effect and the highest mortality rate was 55 %.Considering comprehensively,the microbial pesticide formulation was determined to be wettable powder.The freeze-dried bacterial powder was used as the original drug,and different carriers,RNA enzyme inhibitors,and surfactants were added in turn.The wettable powder was fully mixed with the original drug at different ratios to prepare the wettable powder.The best wettable powder formula was screened as follows : 6 % urea and 7 % calcium lignosulfonate were added successively under the condition of the mass ratio of silica to the original drug of 6 : 1.According to the formula,three kinds of double-stranded RNA engineering bacteria corresponding to Helicoverpa armigera,Plutella xylostella and Spodoptera exigua were expanded and cultured.After being made into finished products,spraying was carried out on the 2nd instar larvae of different pests on the leaves of Chinese cabbage,and the highest 50 %mortality was observed.Then we tried to prepare a mixed preparation that can simultaneously control the three pests.Multiple control groups were set up.The results showed that the leaf surface residual rate of Chinese cabbage after spraying the mixed preparation was 90 %,Du Pont Kangkuan was 100 %,and Bacillus thuringiensis was 98 %,while the blank control and negative control were 40 % and 30 %,respectively.This paper mainly studies how to make the double-stranded RNA engineering bacteria which can cause RNA interference effect to the corresponding pests into microbial pesticide preparations,to achieve productization,and effectively apply RNA interference technology to the prevention and control of pests in the field.