Preparation And Study Of CS/ALG Floating Beads Containing Prometryn

In order to ensure the normal growth of agricultural crops and control the negative effects of pests and diseases,pesticides have become an indispensable agricultural chemical in people’s production and life.In recent years,with people’s continuous attention to food safety issues,the degree of concern for the safety of pesticide use has also increased,and the development of precise,environmentally friendly and safe pesticide controlled release dosage forms has become one of the important contents of pesticide research.Duckweed(Lemna minor L.)is a common aquatic weed,and its invasive growth can lead to reduced yield and quality of rice.Application of traditional herbicides has been a common method for duckweed control,but the applied herbicides often have low control efficiency duo to the low access to target weed,resulting in large amount of residue in water and soil in rice paddy.In this study,natural polymer materials such as chitosan and sodium alginate incorporated with vegetable oil were used to prepare polysaccharide beads with floating characteristics on the water surface as carriers for herbicide prometryn,could precisely target the release of herbicides at the roots of duckweed.The experiment explored the floating performance,storage performance,slow release performance,drug loading performance,and biological safety of the polysaccharide beads..The control efficiency and disspation of the prometryn-loaded beads were compared to commercial prometryn in both laboratory and rice field conditions.Scanning electron microscopy,Fourier infrared spectrometer,gas chromatography tandem mass spectrometry and other testing methods were used to characterize the beads and test the drug loading performance.The results show that the prepared carrier is a bead with a diameter of about 2.5 mm,the tight mesh structure inside the beads can encapsulate prometryn in it,with an encapsulation rate of more than 80%and good storage stability.The prepared beads can float in water for more than 60 days,and can effectively transport pesticide active ingredients and release them around duckweed.The release rate in the paddy field water at p H=6.2 is lower than that in deionized water at p H=7.Compared with the traditional dosage form,the lethality of the drug-loaded beads on zebrafish after 14 days in the water containing 32 mg/L was reduced by about 80%compared with the wettable powder,which effectively improved the pesticide’s Biological safety.Field experiments show that compared with traditional wettable powders,the use of floating beads was mainly enriched in duckweed,the enrichment rate is more than 50%,and the enrichment rate is lower in rice and soil;In terms of residual digestion,the use of floating beads to prolong the pot life of duckweed in duckweed was significantly longer than the use of wettable powders.The control efficiency of prometryn-loaded beads was significantly greater than that of traditional dosage forms,at the dose of 0.038 g a.i./m~2,the prometryn-loaded bead were used to control duckweed.The control effect was more than 95%in 60 days,and the effective ingredient dosage was only 1/5～1/2 of the wettable powder.Our results suggest prometryn in polysaccharide beads can release the herbicidal active ingredient on the surface of the water and reduce adverse impacts on human health and the environment,and that the formulation therefore has potential for use in agriculture and fisheries.