Biodiversity of pests and natural enemies in different production environments of rice and cabbage: impacts of insecticide application

This study aimed to assess the impact of different production systems, including organic, Integrated Pest Management (IPM), and farmer's practices, on the biodiversity of pests and natural enemies in rice and cabbage fields. As noted more detail in the Supplementary Material section S.M.1, the study was conducted over three consecutive seasons during 2016–2018 in Coimbatore, Erode and The Nilgiris districts of Tamil Nadu, India. The rice field survey revealed the presence of 49 species belonging to 31 families under 10 orders, including Insecta, Arachnida, and Acari. Among these, 23 species were identified as pests, 23 as natural enemies, and the remaining as pollinators. The organic ecosystem exhibited the highest relative density, with Scirpophaga incertulas Walker being the most prevalent species in season I (67%), Cnaphalocrcis medinalis (Guenee) in season II (82%), and season III (65%). In cabbage fields, 19 pest species and 12 natural enemies belonging to the class Insecta and Arachnida were identified. The IPM farm showed the highest Shannon-Weiner index values in season I (3), season II (2), and season III (2). The relative density was highest for Plutella xylostella Linnaeus in all three seasons (37% in each season). The analysis of the impact of insecticide application on biodiversity indicated that the use of older and newer molecule insecticides had a negative influence on both pests and natural enemies in rice and cabbage fields. The older molecules showed a higher negative impact compared to newer molecules during all three seasons in rice ecosystems. Similarly, in cabbage ecosystems, the use of both older and newer molecule insecticides had a significant negative impact on pests and natural enemies in all three seasons. These findings emphasize the importance of implementing sustainable production systems in agriculture to minimize ecological disturbance while maintaining yield and quality.