The widespread use of pesticides to enhance agricultural productivity is crucial for ensuring sufficient food supply. Apples, a globally popular fruit rich in phytochemicals with health benefits, are often introduced early into children's diets. Fluxapyroxad, a new systemic carboxamide fungicide, is increasingly used for broad-spectrum fungal disease control. It inhibits succinate dehydrogenase (SDHI) in the mitochondrial respiratory chain, impacting spore germination and fungal growth. While fluxapyroxad's efficacy is established, research on its environmental fate, dissipation, and degradation, particularly the influence of microorganisms, is limited. This study aimed to determine fluxapyroxad dissipation kinetics in apples, focusing on pre-harvest intervals (PHI) to ensure safe residue levels for children. It also investigated whether the biological preparation Myco-Sin could accelerate fluxapyroxad degradation in field conditions, aligning with Integrated Pest Management (IPM) principles.

Several studies have examined fluxapyroxad's behavior in the environment. He et al. (2016) reported half-lives of 9.4–12.6 days in apples and 10.3–36.5 days in soil. Noh et al. (2019) observed a 50% reduction in fluxapyroxad concentration on perilla leaves after seven days. Li et al. (2015) demonstrated that aerobic microorganisms are more efficient in metabolizing fluxapyroxad than anaerobic ones. However, research on the influence of microorganisms, especially yeast, on fluxapyroxad degradation remains scarce. Studies have highlighted the potential of yeast, such as *Saccharomyces cerevisiae*, to degrade other pesticides. Wołejko et al. (2016) showed that yeast accelerated the degradation of strobilurins and carboxamides in leafy vegetables, while other research demonstrates the ability of *S. cerevisiae* to degrade glyphosate and metabolize herbicides atrazine and terbutylazine. The use of *Clavispora lusitaniae* for pendimethalin degradation has also been reported.

A validated GC-ECD method with QuEChERS extraction was used to analyze fluxapyroxad residues in apples. The method was validated according to SANTE guidelines (2019), demonstrating linearity (R≥0.999), recoveries (107.9–118.4%), and low relative standard deviations (4.2–4.7%). Field trials were conducted in 2018 and 2019 using Gala and Idared apple varieties. Apples were treated with the fungicide Sercadis (fluxapyroxad 300g/L), followed by Myco-Sin (a biological preparation containing *Saccharomyces cerevisiae*) application seven days later in one block, while the other block served as a control (water spray). Samples were collected at various time points (12h, 1, 4, 8, 15, 29, 43, and 60 days post-treatment) and analyzed for fluxapyroxad residues. First-order kinetics were used to determine dissipation half-lives. Dietary risk assessment was performed using the PRIMo model (rev. 3.1), estimating the International Estimated Daily Intake (IEDI) and comparing it to the Acceptable Daily Intake (ADI) for different consumer groups (Polish adults, German children, and UK infants/toddlers). Weather data (temperature and rainfall) were recorded throughout the trials.

The validated GC-ECD method effectively quantified fluxapyroxad residues in apples. Initial fluxapyroxad levels after Sercadis application were below the maximum residue limit (MRL) of 0.9 mg/kg (0.417 ± 0.08 mg/kg in Gala and 0.304 ± 0.062 mg/kg in Idared). Dissipation half-lives were approximately 9 days for both apple varieties. To achieve residue levels below 0.01 mg/kg (suitable for baby food), a PHI of 44 days was determined. Myco-Sin application resulted in significant fluxapyroxad degradation, reaching 59.9% and 43.8% on the first day post-application for Gala and Idared, respectively. This effect was statistically significant on day 8. Dietary risk assessment indicated that the exposure to fluxapyroxad residues from apple consumption was below the acceptable safety level (below 9.8% ADI for children and below 1.9% ADI for adults), posing no significant health risk.

This study demonstrates the rapid dissipation of fluxapyroxad in apples, confirming its relatively short persistence in the environment. The established PHI provides a guideline for safe apple production, particularly for infant food. The significant contribution of yeast (Myco-Sin) in accelerating fluxapyroxad degradation supports the implementation of IPM strategies. The low dietary risk assessment further strengthens the safety profile of fluxapyroxad residues in apples for consumers. The findings highlight the potential of biological methods in reducing pesticide reliance and promoting environmentally sustainable agriculture.

This research successfully validated an analytical method for fluxapyroxad residue analysis in apples and determined the rapid dissipation kinetics of fluxapyroxad in two apple varieties. The study demonstrated the efficacy of a yeast-based biological preparation in accelerating fluxapyroxad degradation and confirmed that dietary exposure is within acceptable safety limits. Future research could investigate the specific mechanisms of fluxapyroxad degradation by yeast, explore other biological control agents, and expand dietary risk assessment to include additional consumer groups and geographical regions.

The study was conducted in specific geographical locations and under particular climatic conditions, limiting the generalizability of the findings. The sample size for dietary risk assessment, while incorporating diverse age groups and nationalities, may be further enhanced for a more comprehensive analysis. The study focused on two specific apple varieties, thus the results may not be directly extrapolated to other apple cultivars.