Organic farming of cotton Gossypium hirsutum L. mediates species richness and evenness of generalist predators

Abstract Organic farming is known to enhance the diversity and abundance of biological control agents thus, complements integrated pest management (IPM). There is little published literature from cotton crop grown organically with respect to abundance and diversity of natural enemies. In this study we present the assemblage of arthropods predatory communities from the organically as well as conventionally grown cotton. We noted two Coccinellids species (Coccinella undecimpunctata L., Coccinella septempunctata L.), Formicid, Orius insidious (Say), two spider species (Thomisidae and Araneidae) and Encarsia formosa Gahan in both kinds of fields, but their populations and diversity were more abundant in organically managed fields. In organic cotton, species richness was significantly higher and Simpson dominance was significantly lower compared to conventional counterpart in 2019 and reverse situation was observed in 2021. Moreover, Chrysoperla carnea (Stephen) were observed only in organically grown cotton. Spiders and formicids first appeared almost at the same time when hemipetran pests were recorded. This study demonstrates that organically grown cotton fosters more densities of biological control agents and their species. Our results proved that pest management is triggered by two phenomena in organic farming. First, pest densities are reduced by the number of natural enemy species (species richness) when dominance is lower, and secondly, by the limited number of dominant species present in organic fields when species richness is lower. We also discuss implications of our results for pest management on organically grown cotton in the context of ecosystem services.