Predator-prey association in mono- and dicultures: Effect of maize and bean vegetation

The effect of bean and maize vegetation on the abundance of prey, predators, and predation rate in larvae of the Mexican bean beetle (Epilachna varivestis Mulsant (Coleoptera: Coccinellidae)) was investigated. Prey and predator densities were determined when bean and maize plants were grown alone (monocultures) and when bean plants were intercropped with tall or short maize plants (dicultures). On bean plants, overall densities of aphids, leafhoppers, and thrips and their predators did not differ between mono- and dicultures. Higher numbers of the predators Orius insidiosus (Say) (Heteroptera: Anthocoridae) and Coleomegilla maculata (De Geer) (Coleoptera: Coccinellidae) in maize than bean monocultures did not result in higher densities on bean plants in maize-bean dicultures. Only spiders and nabids (in some samples) were more abundant in dicultures. Data suggest that the predators do not aggregate in habitats with higher bean beetle densities. Nonetheless, the mortality of bean beetle larvae was density independent in bean monocultures and inversely density dependent in a maize-bean diculture. The results therefore suggest that predators have a greater effect on bean beetle populations in dicultures than in monocultures and they reinforce low bean beetle colonization in intercropped habitats.