S14 - Session O1 - Interests of companion plants in apple and peach orchards to control aphids

Authors: Julie Borg *, Laurent Gomez, Guy Costagliola, Hélène Gautier

Aphids are particularly problematic in apple and peach orchards. As part of an agro-ecological approach aiming to manage crops without synthetic pesticides, the introduction of companion plants (CPs) in the crop can be an early lever to control this pest. Some CPs emit volatile organic compounds (VOCs) (Heil and Silva Bueno, 2007; Karban, 2007, Himanen et al, 2010) that repel pests and/or disrupt their demography. Thus, the CPs-crop combination can be an innovative approach to optimize crop protection and reduce pesticide use (Malezieux et al, 2009, Ben Issa et al, 2017b). Laboratory and orchard experiments investigated the effect of introducing CPs into horticultural systems to control aphids. Laboratory tests have been performed to evaluate the ability of CP to disrupt colony development of Myzus persicae , the green peach aphid; Dysaphis plantaginea , the rosy apple aphid; and Aphis Gossypii , the cotton aphid. Volatile organic compounds (VOCs) released by basil, marigold, rosemary, or peppermint can repel aphids and/or decrease their fecundity (Ben Issa et al, 2016 and 2017a; Dardouri et al, 2017, 2019a and b). Genotype, phenological stage or even crop management modify the nature of the olfactory message delivered by these plants, and thus their ability to disrupt aphid traits. A factorial trial in apple orchards showed that the introduction of basil or marigold in pots around the trees decreased the severity of rosy aphids and increased the presence of their natural enemies. A second factorial trial in peach orchards showed that the introduction of peppermint had an impact on the vigor and growth of peach trees without revealing any effect on aphids populations. The concentration of VOCs emitted was relatively low, over short distances. The cutting of the mint in July showed a strong increase in VOC concentration, which presents an interesting management for the next years of experimentation. This study is an important step forward in the knowledge of companion plants and their use by farmers in the coming years.