Field evaluation of biodegradation of boscalid and kresoxim-methyl in grape leaves by plant growth-promoting rhizobacteria

This study investigated the potential of plant growth-promoting rhizobacteria (PGPR) to enhance the dissipation of boscalid and kresoxim-methyl residues in grape leaves under field conditions. The experiment was conducted in a vineyard in Tokat, Türkiye, using the ‘Narince’ ( Vitis vinifera L.) grape variety. Boscalid and kresoxim-methyl were applied prior to harvest, followed by the application of A cinetobacter calcoaceticus , Enterobacter cloacae , Pseudomonas putida , and their combined treatment. Pesticide residues were determined using a validated QuEChERS extraction method coupled with LC–MS/MS analysis. Dissipation kinetics were evaluated using the double first-order in parallel (DFOP) model. PGPR application enhanced pesticide residue dissipation, with the combined bacterial treatment showing the shortest overall DT50 for both active ingredients. The overall DT50 of boscalid decreased from 24.97 days in the control to 18.42 days with the combined treatment, while that of kresoxim-methyl decreased from 3.17 to 1.68 days. At the 14-day pre-harvest interval, the combined treatment resulted in significantly lower residues of both boscalid and kresoxim-methyl than the control. These findings indicate that PGPR application, particularly the combined bacterial treatment, has potential as a complementary approach for enhancing pesticide residue dissipation in grape leaves under vineyard conditions. Further studies are required to elucidate the underlying mechanisms, characterize transformation products, and evaluate their toxicological significance and the consistency of the approach across different seasons and vineyard conditions.