Development of a novel fumigant tablet containing d-(+)-camphor and 1,8-cineole, the dominant constituents of Artemisia subg. Seriphidium, for the management of Solenopsis invicta

The red imported fire ant, Solenopsis invicta Buren, 1972, is a significant invasive pest threatening public health, agriculture, and biodiversity. Our previous study revealed that d-(+)-Camphor and 1,8-cineole, the dominant constituents of Artemisia subg. Seriphidium exhibits promising fumigant activity against S. invicta. However, their rapid volatility limits their broader application, requiring innovative formulations for sustained release and environmental compatibility. To address this issue, we developed a slow-release tablet formulation that offers an eco-friendly solution for S. invicta management, reducing environmental impact and promoting sustainability. The tablet ensures controlled release with uniform volatilization, while individual constituents exhibit rapid volatilization. The morphological analysis of the fumigant tablet revealed a rough surface and granulation characteristics that facilitate uniform volatilization. The XRD and TGA analyses confirmed the crystalline structure and thermal stability of the formulation. Stability studies using GC–MS demonstrated minimal degradation over 12 months of storage in an air-tight container, with slight losses of 3.5% d-(+)-Camphor and 2.40% 1,8-cineole. FTIR analysis confirmed the presence of characteristic peaks for both d-(+)-camphor and 1,8-cineole, validating their incorporation in the fumigant tablet. The toxicity evaluation indicated the tablet has significant efficacy against workers and alates, with LC50 values ranging from 0.71 to 17.35 mg/L. The tablet achieved 100% mortality against workers at 0.22 g/L in 120 min, while alates required 0.29 g/L and 300 min in a substrate-free fumigation container. Furthermore, under laboratory-simulated field conditions using single ant mounds, the tablet achieved 100% mortality of all life stages of S. invicta at a concentration of 2.5 g/kg soil after 96 h. Our study highlights the potential of bioactive phytochemicals in sustainable pest management, paving the way for eco-friendly solutions. The findings will significantly contribute to developing a novel fumigant tablet effective against S. invicta, with potential applications extending to various stored grain pests, thereby fostering a more environmentally conscious approach to sustainable pest control.