S14 - Session O1 - How the use of companion plants can improve the colonization of tomato crop by Macrolophus pygmaeus, in the context of soilless production?

Authors: Benjamin Gard *, Amélie Bardel, Marion Diemer, Mélina Archinard

The mirid bug Macrolophus pygmaeus is the main natural enemy used in protected tomato crop. This predatory bug attacks various tomato pests including Trialeurodes vaporariorum . However, in soilless greenhouse, the establishment of M. pygmaeus is long, and some pests may colonise the crop more rapidly, sometimes leading to protection failure. To improve the establishment of this natural enemy, the use of companion plants has been studied, with encouraging results in soil crop. However, this method has not yet been transferred to soilless crop. To identify companion plants that are favourable to the development of M. pygmaeus and adapted to the context of soilless production, we conducted two co-construction workshops with soilless tomato growers, combined with a screening of companion plants at laboratory scale. Three species were then selected : Calendula officinalis , Ballota hirsuta , Geranium macrorrhizum and tested in experimental greenhouses, in a 2 year experiment. A strategy of pre-installation of M. pygmaeus on the selected companion plants was evaluated, in comparison with a classical release strategy. M. pygmaeus was introduced on the three selected plant species 30 days before their introduction into tomato crop. Tomato plants were artificially infested with adult females of T. vaporariorum 15 and 10 days before the introduction of the companion plants in the greenhouse. The results showed that the pre-installation strategy with companion plants influenced the establishment of the natural enemy in two ways. Firstly, it allows an earlier installation of M. pygmaeus on the crop and secondly, it contributes to increase the population of M. pygmaeus compared to the control strategy. The species of the companion plant also influences the establishment and population dynamics of M. pygmaeus . Indeed, marigold plants led to a higher peak population of the mirid bug. However, whitefly control was not sufficient, but this could be due to excessive artificial infestation.