Impact of agricultural diversification on the insect community of cruciferous crops

Abstract

Numerous studies have examined the responses of pest and beneficial arthropods to plant diversification in ephemeral cropping habitats. Cruciferous crops, mainly cabbage and broccoli, are probably the most studied plants with respect to evaluating the impact of plant mixtures on insect population dynamics. This review examines the mechanisms influencing arthropod responses to floral diversification, specifically focusing on cruciferous crops. In many instances, mechanisms accounting for herbivores and natural enemy responses to plant mixtures are not thoroughly tested. Biological parameters of herbivores impacted by crop diversification were mainly related to the behavior of the insects studied. Mechanisms accounting for herbivore responses to plant mixtures include reduced colonization, reduced adult tenure time in the marketable crop, and oviposition interference. Tactics used for choosing companion plants, and the future perspective for mixed-crucifer crops usage are discussed. Manipulative studies involving cruciferous crops provide some evidence that habitat manipulation techniques (e.g., intercropping, undersown nonhost plants, vegetation borders) impact crop growth. However, the indirect role habitat manipulation plays in the population dynamics of insect pests and natural enemies still remains unclear in many systems. Quantitative data are needed to determine the level of change in plant quality brought about by companion planting that alters arthropod behavior.