Construction Of Environmental-responsive Pesticide-loading System For Plant Disease Control

Pesticides are an important material foundation for ensuring food security and world peace and stability,and the rigid demand for pesticides in human production and life has persisted for a long time.However,in the agricultural production process,traditional pesticide formulations are easily lost in the environment through drift,runoff,leaching,and other pathways.Pesticides that persist on the leaf surface or are absorbed and transported by plants are also easily metabolized and inactivated,leading to a short duration of pest control effectiveness.In addition,excessive and repetitive use of pesticides to achieve ideal control effects can lead to issues such as resource wastage and environmental pollution.Based on the interactive relationship and mechanism among crops,pests and diseases,and pesticides,combined with the interdisciplinary background of chemistry and plant protection,an innovative intelligent release pesticide system is constructed with a pest and disease habitat stimulation response.This system aims to achieve targeted delivery,dose release,sustainable control,and reduced usage with increased efficacy,breaking through the important problems of short pesticide efficacy and high frequency of application.This paper focuses on the issues of"high application but low efficiency",low target efficiency,and poor persistence of conventional pesticide formulations.Based on the outbreak patterns of different plant diseases and the scenarios of pesticide application,a functional pesticide-controlled release drug delivery system was constructed,which utilizes the changes in the microenvironment of the plant during the invasion of the pathogen as a trigger for pesticide release.The aim of this research is to develop environmentally friendly pesticide formulations.The research findings are as follows:Firstly,based on the characteristics of the easy outbreak of soybean Phytophthora root rot in high humidity environments,and the shortcomings of large irrigation amounts and poor persistence of root irrigation and medication,a targeted approach was taken to construct a medicated film that can dissolve in water and slowly release a fungicide to effectively prevent and control soybean Phytophthora root rot.A fungicide-loading films was prepared by blending natural biodegradable polymers chitosan（CS）and hydroxypropyl methylcellulose（HMPC）at different mass ratios,and adding the fungicide metalaxyl（Me）andβ-cyclodextrin inclusion complex.By evaluating the tensile properties,water solubility,and transparency of the prepared films,it was determined that the drug-loading film(Me-CS₅₀/HPMC₅₀)prepared with a quality ratio of CS to HPMC of 1:1 exhibited the best physical properties.The results of the in vitro release experiment showed that the film containingβ-cyclodextrin can effectively regulate the release rate of Me in water.In vitro and in vivo bioactivity experiments shown that the Me-CS₅₀/HPMC₅₀ can effectively reduce the incidence of soybean phytophthora root rot.Secondly,based on the acid production mechanism of the Sclerotinia diseases during infection of canola and the drawbacks of low persistence and easy off-target effects of foliar spray application,a novel nanocomposite with dual responsiveness to light/p H,high dispersibility,and water-based formulation was designed for effective control of oilseed rape Sclerotinia disease.In this study,prochloraz（Pro）and p H-jump reagent 2,4-dinitrobenzaldehyde were encapsulated into ZIF-8 nanoparticles（PD@ZIF-8）using a simple one-pot method.The p H-jump reagent can induce the acid decomposition of ZIF-8 under UV light,thus achieving the controllable release of Pro.The experimental results showed that after 36 hours of UV irradiation,the release rate of PD@ZIF-8 was 63.4±3.5%,while it was only 13.7±0.8%under dark conditions.In vitro bioassay experiments showed that the EC₅₀ of PD@ZIF-8 irradiated with UV light against Sclerotinia sclerotiorum was 0.122±0.02μg·m L^-1,which was not significantly different from the activity of Pro.In pot experiment,it was found that after leaf spraying treatment for 14 days and inoculation,PD@ZIF-8 treatment still had an efficacy of 51.2±5.7%against Sclerotinia disease,while the commercial emulsion had only 9.3±3.3%.In addition,through the use of fluorescence tracking,ZIF-8 can effectively regulate the distribution of Pro in the body of oilseed rape,and it is relatively safe for both plants and Hep G2 cells.Finally,based on the characteristics of the susceptibility of tomato bacterial wilt to outbreaks in acidic soils,and the shortcomings of poor efficacy of root administration and easy loss of pesticides,a novel acid-responsive microsphere was synthesized to achieve efficient and synergistic control of tomato bacterial wilt.In this study,a p H-responsive core-shell microsphere（Ber@Zn O-Z）was prepared using Zn O microspheres as the core,ZIF-8 as the shell,and berberine（Ber）as the model fungicide via an in-situ crystal growth method.The microsphere can rapidly release berberine in acidic environments,responding to the soil p H that is prone to tomato bacterial wilt outbreaks.In vitro antibacterial experiments showed that Ber@Zn O-Z had a synergistic effect on the inhibition of Ralstonia solanacearum,with 4.2 times and 1.8 times higher activity than Ber and the carrier Zn O-Z,respectively.Mechanism analysis revealed that Ber@Zn O-Z can induce the production of ROS,resulting in bacterial DNA damage,cytoplasmic leakage,and changes in cell membrane permeability.This makes the released Ber more easily penetrate the membrane and bind with DNA,thereby synergistically producing highly effective bactericidal activity with the Zn O-Z carrier.The pot experiment also showed that Ber@Zn O-Z can significantly reduce the severity of tomato bacterial wilt disease.On the 14th day after inoculation,the disease index of tomatoes treated with Ber@Zn O-Z was only 45.8%,while berberine treatment was as high as 94.4%.In addition,the study found that Zn O-Z did not accumulate in the aboveground parts of plants and has no effect on plant growth.This paper investigates the construction of a pesticide delivery system for fungicides based on the changes in microenvironment during plant disease occurrence or pathogen infection.This approach improves issues such as off-target pesticide application,short effective period,and low utilization efficiency,enriching and developing the theory and technology system of pesticide controlled-release.It provides a reference basis for the development of new pesticide formulations,and contributes to the sustainable development of China’s pesticide industry and the promotion of reducing pesticide use while increasing efficiency.