Cécile Bresch

Secondary plants used in biological control: A review

In crop systems, different types of plant or secondary crop may be grown together with the primary crop for pest management purposes. These additional plants – henceforth called secondary plants – may increase the efficiency and sustainability of biological control of pests by natural enemies. Such plants fall into several categories: companion, repellent, barrier, indicator, trap, insectary, and banker. Despite their effectiveness and accepted function in biological control, to date the full potential of secondary plants in integrated pest management has not been put to good use. This may be partly attributed to a lack of detailed knowledge of the way the secondary plant–crop systems operate, including the effects of the secondary plants on tritrophic interactions. The biggest constraint upon progress, however, has been confusion over definitions and terminology. In this paper, we review the knowledge of the currently employed plant categories and provide clear definitions.

Functional characteristics of secondary plants for increased pest management

Secondary plants may be added to a cropping system for the purpose of improving pest control. In a recent article (Parolin P, Bresch C, Brun R, Bout A, Boll R, Desneux N, Poncet C (2012) Secondary plants used in biological control: a review, International Journal of Pest Management 58, 91–100) we defined different categories of secondary plants used to enhance biological control: companion, repellent, barrier, indicator, trap, insectary, and banker plants are intentionally added to agricultural systems in order to improve pest management through either top-down or bottom-up processes. In the present paper, we focus on the functional characteristics of secondary plants and on the mechanisms which contribute to reducing the presence of pests. If we understand and integrate the effects that such plants have on pests and beneficial arthropods, together with the multitrophic interactions in which these organisms are involved, the application of pesticides in crop systems can be reduced and enhanced productivity in agro-ecosystems achieved. Here, we identify the main characteristics of, and the prerequisites for, plants which can enhance crop protection in agro-ecosystems.