Intercropping cotton with wheat or maize enhances biological pest control but only intercropping with wheat improves cotton yield

Intercropping is a promising strategy for ecologically based pest management in field crops. However, its effects on pest suppression and crop yield vary across species combinations, requiring experiments to identify context-specific driving principles and guide practical application. We evaluated the effects of intercropping cotton with spring wheat or maize on pest suppression and yield. Aphid and natural enemy populations were monitored in intercropped and sole cotton, and predation activity was assessed using cotton bollworm egg cards. Cotton yield was also measured. Aphid densities on cotton were 63 % lower in both cotton-wheat and cotton-maize than in sole cotton in 2023, and 24 % and 29 % lower in cotton-wheat and cotton-maize than in sole cotton in 2024. No significant difference was observed in cotton aphid control between the two intercrops in either year. Ladybeetle densities during early cotton aphid population build-up were higher in the two intercrops than in sole cotton. The predation rate on cotton bollworm eggs was 10 % - 178 % higher in intercrops with wheat and maize. Cotton yield was 18 % higher in cotton-wheat but 18 % lower in cotton-maize than in sole cotton. Different strength of interspecific plant competition is the likely key driver for the difference in yield impact of the two companion species. We conclude that both spring wheat and maize enhance natural enemies and reduce aphid populations in cotton, but only intercropping with wheat enhanced cotton yield. Results indicate that cotton-cereal intercropping is a robust strategy to suppress cotton aphid and reduce reliance on insecticides, but interspecific plant competition needs to be considered to ensure cotton yield.