Associational Resistance in Squash Monocultures and Polycultures in Tropical Mexico

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Abstract
Herbivore densities, weed composition and abundance, and crop yields per land unit were compared between squash monocultures and traditional maize/legume/ squash polycultures in tropical Mexico. The most abundant insect pest in the system, Diaphania hyalinata (L.) (Lepidoptera: Pyralidae), generally had lower population densities in polycultures than in monocultures. The squash bug, Anasa tristis (De Geer) (Heteroptera: Coreidae), tended to be more common in polycultures. Reasons for the observed patterns of squash herbivore densities are discussed in terms of the “resource concentration” hypothesis. Weed height and biomass were significantly greater in monoculture and, although yields of each component crop were decreased, total crop yields were higher in polycultures when estimated as a land equivalent ratio.