Agro-ecological approaches in soil-less rosebushes under cover for a crop with low levels of phytosanitary inputs -ROSA BIP Project

This issue follows on from the “Carrefour de l'innovation agronomique” dedicated to the results of DEPHY EXPE 2 projects - Systems using pesticides as a last resort: results and lessons from 6 years of experimentation.

International audience

anglais. The cultivation of roses, a major ornamental species, faces numerous pest and disease challenges, some of which, like thrips, question the economic viability of the cropping system. Chemical control leads to very high Chemical auTreatment Frequency Index(TFI), especially in cut flowers. The implementation of biological control has significantly reduced this TFI, but still struggles with the control of the Western FlowerThrips Frankliniella occidentalis (WFT), aphids, Bemisia tabaci, mites and powdery mildew.<p>This project aimed to observe the effectiveness of innovative global protection strategies based on biological control combined with physical control (particularly suction) and the use of biocontrol products. This combined approach is evaluated for a soilless rose cultivation system for cut flower (in Hyères-83 and Nice-06) and for a container nursery rose production system under unheated shelter (in Saint Pol de Léon -29).</p><p>While these strategies have proven insufficient to fully control WFT and aphids in cut flower cultivation, they have shown very promising advancements. For container nursery roses, pest control by the combination of levers studied could be better established, resulting in a significant decrease in TFI without additional damage. In nursery roses, the implementation of an annual vacant space during crop rotation greatly enhances the effectiveness of alternative strategies, a practice not feasible in cut flowers due to their multi-annual cultivation.</p><p>The improvement of the biological control efficiency against aphids is attributed to the use of companion plants, better consideration of host specificity for parasitoids selection, and the implementation of more appropriate decision rules for the application of biocontrol products in treatments located on the foci during the appearance of imbalance between pests and beneficials. Against thrips, enhancing the biodiversity of Phytoseiids, particularly through their feeding habits, and the preventive association of beneficial acting on the aerial parts of plants and another to combat thrips nymphal stages have proven to be very useful tools that can be combined with the application of biocontrol products (Beauvaria bassiana strain GHA -Botanigard 22wp®) which have been shown to be effective against this pest during the summer season.</p><p>Similarly, against rosebush powdery mildew, the combined application of certain biocontrol and biostimulant products to strengthen foliage cuticles has significantly reduced the risk of disease onset in unheated shelter. This article presents a summary of the most significant findings of the project.</p>