Intercropping of companion plants (CPs) that release distinct volatile compounds with horticultural crops has been proposed to improve pest management. Although CP extracts or essential oils have been reported to be efficient in disturbing the settling of insects such as aphids, the effect of using actual CPs remains relatively unknown. Our aim was to screen odorous CP species for their effect on the performance of green peach aphid,Myzus persicae Sulzer (Hemiptera: Aphididae), when released on adjacent pepper plants. Intercropping was tested in growth chambers using potted plants to avoid root interactions and homogenise the abiotic environment of CPs. Our results indicated that eight CP species—rosemary, African marigold, French marigold, geranium, lavender, basil, chives, and pot marigold—affected aphid performance by reducing the reproductive performance and/or settlement of females. Rosemary followed by African and French marigold was associated with the largest reduction in adult female and nymph number. Chemical analyses indicated that rosemary and French marigold emit specific volatiles. In contrast, four CP species (false yellowhead, thyme, savoury, and peppermint) were not associated with a significant change in aphid performance and emitted a lower diversity of volatiles. This screening of CPs under controlled conditions may be considered as a first step towards the identification of volatiles emitted by actual plants that can affect aphid performance and help the choice of CPs to optimise intercropping strategies
1 Companion plants (CPs) may affect the performance of pests on their hosts because of their potential to emit volatile organic compounds (VOCs) and their effectiveness depends not only on the species, but also on their arrangement in the crop system. 2 The present study aimed to evaluate the effect of intercropping rosemary, lavender or basil on the performance of Myzus persicae populations on sweet pepper plants (Capsicum annum) under greenhouse conditions. 3 In a first set of experiments, sweet pepper plants were neighboured by either one or two CPs. In another set of experiments, rosemary was tested at three distances (0.5, 1.5 and 2.5 m) from the host plant. 4 The first set of experiments showed similar patterns of aphid performance (i.e. number of females and nymphs) when a sweet pepper plant was surrounded by one or two companion plants. However, aphid performance was affected more when sweet pepper plants were intercropped with rosemary compared with lavender or basil. 5 The effect of the companion plant decreased significantly with distance. Rosemary was most effective at 0.5 m, although its effectiveness decreased at 1.5 m, becoming insignificant at 2.5 m. 6 The results suggest that a CP may be effective under greenhouse conditions provided that it is located near the target plant.
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