Preparation and performance study of Lambda-cyhalothrin sustained-release microcapsules based on composite gel method

In response to the growing need for improved pesticide formulations that offer enhanced controlled-release properties and greater application stability, this research focused on developing an advanced microencapsulated delivery system for lambda-cyhalothrin. The investigation employed a sophisticated complex coacervation methodology, utilizing lambda-cyhalothrin as the core active ingredient while selecting gelatin and gum arabic as the complementary wall-forming materials. This combination was strategically chosen based on their demonstrated compatibility and ability to form stable coacervate systems under precisely controlled environmental conditions.The experimental approach encompassed a comprehensive investigation of multiple critical processing parameters that significantly influence microcapsule characteristics. Through systematic analysis using scanning electron microscopy (SEM), the research thoroughly examined how variations in pH levels, processing temperature, wall material mass concentration, emulsifier type and concentration, crosslinking agent implementation, and crosslinking agent mass percentage affected the morphological development and structural integrity of the resulting lambda-cyhalothrin microcapsules. The morphological assessment provided crucial insights into the formation mechanisms and helped identify optimal processing conditions. Additionally, the study incorporated detailed simulated release experiments under controlled laboratory conditions and comprehensive bioassay testing against target insect species to rigorously evaluate the release kinetics and insecticidal efficacy of the formulated microcapsules.Results from the extensive experimental trials revealed a specifically optimized parameter combination that yielded microcapsules with superior morphological characteristics and performance attributes. The ideal formulation conditions were determined to be: a wall material mass fraction maintained precisely at 2%, a carefully controlled curing temperature of 15 ℃, and a crosslinking agent (glutaraldehyde) mass fraction established at 0.8%. Under these meticulously maintained processing conditions, the resulting lambda-cyhalothrin microcapsules demonstrated exceptional structural integrity and morphological perfection. The microcapsules exhibited highly uniform spherical morphology with remarkable consistency in size distribution, displayed exceptionally smooth surface topography without visible imperfections, maintained excellent dispersion characteristics without significant agglomeration, and showed minimal incidence of shell fracturing or structural defects. The encapsulation efficiency achieved with this optimized formulation reached an impressive 89.47%, indicating highly effective core material incorporation and retention within the wall matrix structure.The controlled-release properties of the microencapsulated formulation were quantitatively evaluated through standardized release testing in methanol-water solution systems, providing crucial insights into the release kinetics and potential field performance. The results demonstrated that the lambda-cyhalothrin microcapsules exhibited a substantially sustained and prolonged release profile, with a cumulative release rate of merely 58% over the critical 24-hour evaluation period. In striking contrast, the conventional lambda-cyhalothrin emulsifiable concentrate formulation displayed nearly complete and rapid release (over 95%) within the identical evaluation period. This remarkable differential in release behavior provides compelling evidence for the significantly enhanced sustained-release capability achieved through the microencapsulation approach, confirming the effectiveness of the complex coacervation method in modifying and controlling the release kinetics of the active ingredient.Biological efficacy assessment conducted through standardized laboratory bioassays against diamondback moths (Plutella xylostella) further validated the superior performance characteristics of the microencapsulated formulation. The lambda-cyhalothrin microcapsules demonstrated substantially improved insecticidal activity and notably prolonged efficacy compared to the conventional formulation. Particularly significant was the performance observed on the third day post-application, where the insecticidal activity of lambda-cyhalothrin microcapsules was 2.02 times greater than that of the lambda-cyhalothrin emulsifiable concentrate. This enhanced and sustained biological performance underscores the significant advantages of the microencapsulation approach in maintaining effective insect population control over an extended duration while potentially reducing application frequency and environmental impact.This comprehensive investigation successfully demonstrates the effective development and systematic optimization of lambda-cyhalothrin microcapsules utilizing the complex coacervation method with gelatin and gum arabic as wall-forming materials. The research provides substantial evidence that microencapsulation technology represents a highly promising and viable strategy for addressing persistent challenges associated with conventional pesticide formulations, including inadequate utilization efficiency, excessive application requirements, and unintended environmental contamination concerns. The findings offer valuable scientific insights and establish a robust methodological framework for advancing the development of novel, high-efficiency pesticide formulations with enhanced environmental compatibility and improved application characteristics. The successful implementation of this microencapsulation approach creates new opportunities for developing sustainable crop protection strategies and contributes significantly to the ongoing advancement of precision agriculture technologies and integrated pest management systems.