Study On Construction And Adhesion Mechanism Of Foliar Adhesive Pesticides Delivery System

Pesticides play an irreplaceable role in agriculture activities during long human history.Yet,there are some shortages of the traditional formulations were disclosed after long period experience such as poor adhesion,less deposition and low stability in the surrounding.Nearly 60-70%of the pesticide droplets fail to reach the targeted leaf surface,and the effective dose rate of reaching the targeted harmful organisms is less than 0.1%.In order to achieve the purpose of preventing and controlling targeted harmful organisms,the sprayed pesticide formulations have to be applied with high-frequency,which increases the threat to the safety of ecological environment system.It ultimately threatens human life through enrichment effect via delivery of the food chain.Therefore,it is one of the most direct ways to improve the utilization rate of pesticides by effectively enhancing the adhesion and deposition of pesticide droplets on targeted crop leaves and reducing the loss.Given the cost and multiple processes during the spraying process,in this study,the nano science and technology were used to enhance the adhesion ability of pesticide particles and the crop leaf surface by nanosizing pesticide particles and modifying the pesticide particles surface with nanomaterials.We investigated the adhesion mechanism between tannic acid（TA）and layer double hydroxides（LDHs）-coated pesticide particles and crop leaf surfaces in detail.The results showed that the prepared chlorantraniliprole nanosuspension formulation has a better wettability than the commercial water-dispersible granule（WDG）formulations,and after WDG and suspension surface modification of TA and metal ions chelating and LDHs,foliar adhesion was improved alomgwith effectively reducing pesticides loss caused by droplet bounce during spraying process.This study provides a simple and efficient way to improve the pesticide retention efficiency rate on crop leaves,and offers scientific guidance on enhancing the stability and utilization efficiency of pesticides.The results showed as following:1.The 5.0%chlorantraniliprole nanosuspension was prepared by the wet milling method.The particle size,zeta potential,poly dispersity index were 181.1±3.8 nm,-32.0±1.28 mV,0.16±0.02respectively.This nanosuspension formulation showed better storage stability under 4℃,25℃and 54℃conditions,and better wettability on the cucumber and lettuce foliage than WDG formulation.2.The particles of WDG pesticides were coateded by the complex of TA/Fe³⁺.After modification,avermectin（Av）and azoxystrobin（Az）WDG showed good sustained release feature.The wettability and retention rate on crop leaves have been significantly improved.The retention rate was enhanced more than 10%compared with uncoated Av and Az WDG.The biological activity against the targeted myzus persicae and fusarium oxysporum from cucumber are both increased by nearly 1.5 times.The Av-TA also showed better photodegradtion ability that could extend the persistence effect period.Using various concentrations of urea solution to wash the leaves of the sprayed pesticide,the retention rate decreased alongwith the increase of urea concentration,proving the TA modified pesticide particles interacted with the foliage through hydrogen bonding.3.LDHs nanomaterials have the positive electric effect and the characteristics of polyhydroxyl groups,and the pesticide fomulations adhered by"double-sided tape"was constructed by hydrothermal coprecipitation method.The LDHs interacted with pesticides by electrostatic attraction to form foliar adhesive pesticide formulations,which adhered to the leaf surface through hydroxyl groups.This foliar adhesive pesticide formulations exhibited excellent sustained-release behavior,and the retention rate on the various crops leaf surfaces exceeded 50%.Using different concentrations of urea treatment,the retention rate on the leaf surfaces of cucumber and lettuce showed a significant decrease alongwith the increase of concentration.The biological activities of foliar adhesive pesticide formulations on targeted harmful organisms were improved.The better adhesive ability and control release features not only improved the utilization rate,but also reduced the risk of environmental pollution.