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Traitement phytosanitaire des arbres par micro-injection : résilience de la blessure, transfert des molécules et efficacité

Abstract : Trunk injection of plant protection products (PPP) into trees is an alternative method to aerial spraying. This method consists in placing PPP in the vascular system, the sapflow ensuring the dispersion of the molecule in the tree. The random efficacy results of these methods require a better understanding of the transfer and distribution of PPP in the tree in order to optimize treatments. A non-invasive method, the micro-injection with a small diameter needle, was used in this project to determine the resilience of the injection wound caused by the needle. Wounds were analyzed by imaging on sections of apple tree trunks and vines. The establishment of physico-chemical barriers was observed on apple trees. The wound is then isolated from the external atmosphere by compartmentalization of a limited impacted tissue area and a quite rapid resilience of the wound. The distribution kinetics of three active ingredients (a.i) difenoconazole, imidacloprid and pyrimethanil, was monitored after injection in apple trees. Analyses by LC-MS/MS showed a high variability in the foliar distribution of a.i. and concentrations in fruits were below the maximum residue limit. Dyes or radiolabeled PPP were used to study the parameters that control the distribution. These results showed that sectorization of the vascular system and patterns of water flow govern the spatial distribution. In addition, the retention of a.i. on xylem vessels is the main factor explaining the low transfer of some a.i. which can be improved by using surfactants. Furthermore, the efficacy of three others a.i., thiabendazole, allicin and silver nanoparticles, has been tested invitro against various pathogenic fungi to be used by injection. Thiabendazole, which had the highest efficacy, and allicin appeared to be good candidates for this purpose. This work showed that micro-injection was a lasting treatment method without risk for the trees. Further progress in PPP formulations are nevertheless still needed to achieve sufficient efficacy.
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Cyndel Berger. Traitement phytosanitaire des arbres par micro-injection : résilience de la blessure, transfert des molécules et efficacité. Sylviculture, foresterie. Université Paul Sabatier - Toulouse III, 2019. Français. ⟨NNT : 2019TOU30259⟩. ⟨tel-02965816⟩

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