Preparation Of Nano-adjuvant MON@PDA And Synergistic Effect On Insecticide

Chemical pesticides is an important means to address global food security threats.However,due to the long-term unscientific and irrational use of chemical insecticides,agricultural pests have developed different degrees of resistance to the effective components of various insecticides,causing enormous pressure on prevention and control.It is urgent to develop new prevention and control strategies with green and high quality.Pesticide barrel additives play an important role in reducing the amount and enhancing the effectiveness of pesticides.Based on this,using mesoporous organosilica nanoparticles(MON)surface-encapsulated with polydopamine(PDA)to successfully prepare the pesticide nano-adjuvant MON@PDA.Furthermore,the synergistic effect of MON@PDA synergistic insecticides on the virulence of Nilaparvata lugens,Aphis gossypii and Spodoptera frugiperda was investigated,and the synergistic mechanism of MON@PDA synergistic insecticides was preliminarily explored.The main results are as follows:1.MON with a particle size of about 20 nm were synthesized by the one-pot method using cetyltrimethylammonium bromide as a template,tetraethyl orthosilicate and bis-[3-(triethoxysilyl)propyl]-tetrasulfide as silicon sources.Nanohybrid MON@PDA was successfully prepared by dopamine hydrochloride modification.The nanohybrid MON@PDA was successfully prepared.The nanohybrid was characterized by transmission electron microscopy,scanning electron microscopy,Fourier transform infrared spectroscopy,thermogravimetric and differential thermal analysis and Brunauer-Emmett-Teller.The results showed that MON@PDA had uniform particle size and good dispersion,and the encapsulation rate of PDA was 6.7%.2.The effect of MON@PDA synergistic insecticides on the virulence of N.lugens was determined based on rice-seedling dip method.The insecticide-resistant strains of N.lugens(clothianidin-resistant,sulfoxaflor-resistant and nitenpyram-resistant strains)obtained by multi-generation screening in the laboratory and the Xinzhou field-strain of N.lugens were selected to explore the synergistic effect of MON@PDA synergistic insecticides.The results showed that under the co-treatment of MON@PDA and insecticides,the sensitivity of N.lugens resistant strains(clothianidin-resistant,sulfoxaflor-resistant and nitenpyram-resistant strains)to insecticides(clothianidin,sulfoxaflor and nitenpyram)was significantly increased by 1.79-2.11 times,and the sensitivity of N.lugens field strain to a variety of field commonly used insecticides(chlorpyrifos,imidacloprid,clothianidin,dinotefuran,sulfoxaflor,nitenpyram and thiamethoxam)was significantly increased by 1.35-1.96 times.The effects of MON@PDA on the insecticide sensitivity of the sulfoxaflor-resistant strain of A.gossypii and the Jingzhou field-strain of S.frugiperda were further determined.The results showed that MON@PDA significantly increased the sensitivity of the sulfoxaflor-resistant strain of A.gossypii to sulfoxaflor(3.61 times).In addition,MON@PDA significantly increased the sensitivity of the Jingzhou field strain of S.frugiperda to chlorantraniliprole(1.78times)and to lufenuron(2.10 times).3.The synergistic mechanism of MON@PDA synergistic insecticides on pests was further explored.The results showed that MON@PDA had SOD-like enzyme activity and significantly reduced the ROS content in clothianidin-resistant,sulfoxaflor-resistant and nitenpyram-resistant strains of N.lugens.In addition,MON@PDA significantly inhibited the activity of cytochrome P450 enzymes in the clothianidin-resistant,sulfoxaflor-resistant and nitenpyram-resistant strains of N.lugens,and significantly inhibited the expression of CYP6ER1 in the clothianidin-resistant strain,nitenpyram-resistant strain,sulfoxaflor-resistant strain and field-strain of N.lugens.Meanwhile,MON@PDA also significantly inhibited the expression of CYP6CY19 in the sulfoxaflor-resistant strain of A.gossypii.These findings suggested that MON@PDA affects the resistance of pests by scavenging ROS in pests and inhibiting the expression of key P450 genes.