S15 - Session P1 - Design and evaluation of strategies using repellent or deterrent plants to protect leek crops against Thrips tabaci

Authors: Sébastien Picault *, Thibault Nordey, Thomas Deslandes

The thrips Thrips tabaci is a major problem for leek growers because it causes silvery spots on plant foliage which lead to commercial downgrading. To protect leek crops against T. tabaci , several techniques have been tested (release of predatory mites, spraying kaolin on plant foliage, massive irrigation, insect-proof nets, biological control by conservation, mulching, etc.) but none has never been shown to be effective enough to satisfy producers. As part of the REPULSE project, a new technique is being explored: protecting leek crops against T. tabaci by using repellent plants or by masking the odor of leek with the smell of other plants. Since 2020, work has been carried out by CTIFL and Terre d'Essais in order to (i) identify plants inducing get-away behavior in T. tabaci (olfactometry tests under controlled conditions) and (ii) to evaluate plant associations (combination of leek with repellent or deterrent plants) that significantly disrupt the recognition process of leek crops by T. tabaci . The results obtained so far show that most of the repellent plants mentioned in the literature do not repel T. tabaci when they are combined with leek in a field, and that it is very difficult to find effective repellent plants against T. tabaci . However, olfactometry tests carried out by CTIFL at the end of 2021 suggest that one plant could significantly repel T. tabaci under controlled conditions. This plant will be tested in the field in 2022 to see whether or not it can reduce summer outbreaks of T. tabaci below the threshold of economic harm.