The Effect of Storage Conditions and Periods on The Laboratory and Field Efficacy of Some Insecticides

Abstract

This study investigates the impact of storage temperature on the physical stability and insecticidal efficacy of selected pesticide emulsions. Laboratory results revealed a consistent increase in the separation layer thickness of pesticide formulations stored under both high (50°C) and low (-5°C) temperatures. The impact was more severe at elevated temperature, where the thickness exceeded the permissible limit of 2 cm for thiamethoxam and abamectin after three months of storage, and for lambda-cyhalothrin after two and three months. In contrast, cold storage at -5°C maintained the separation layer within acceptable specifications for all tested pesticides. A strong negative correlation was observed between separation layer thickness and insecticidal efficacy, with longer storage durations leading to greater physical degradation. These findings suggest that high temperatures accelerate chemical degradation or alter the target insect's response, ultimately reducing pesticide performance. This outcome aligns with previous research by Bajwa and Sandhu (2014), Laskowski et al. (2017), and Scott & Georghiou (1986), who reported that elevated storage temperatures induce physical changes—such as increased viscosity and phase separation—which directly affect the pesticide's stability and bioefficacy. Although cold storage also caused physical changes, its impact on efficacy was less pronounced. Prior studies (University of Minnesota Extension, 2020) (Guo et al, 2018) confirm that temperatures below 5°C may lead to phase separation, crystallization of active ingredients, and increased viscosity, which could reduce pesticide uniformity and effectiveness upon application. In conclusion, while both high and low temperatures influence the physical properties of pesticide formulations, elevated temperature poses a greater risk to their stability and efficacy, highlighting the critical importance of optimal storage conditions.