Dynamics and residues of difenoconazole and chlorothalonil in leafy vegetables grown in open-field and greenhouse

Lettuce and pak choi are major leafy vegetable crops grown globally. They are susceptible to a wide range of fungal pathogens, which cause severe disease symptoms and decrease yield and quality. Difenoconazole and chlorothalonil are important broad-spectrum fungicides used to manage fungal diseases in leafy vegetables. The dynamics and residues of difenoconazole and chlorothalonil applied on lettuce and pak choi were investigated. The degradation of difenoconazole and chlorothalonil in leafy vegetables under open-field and greenhouse conditions fitted the first-order kinetic equation, with half-lives varying between 2.09–3.07 days and 3.81–6.54 days, respectively. The terminal residues in leafy vegetables were performed by different spraying times under open-field. The residue levels of difenoconazole and chlorothalonil sprayed one to three times on leafy vegetables were lower than the maximum residue limits (MRLs) with seven and twenty-one interval days, respectively. The dietary risk assessment was performed using risk quotient (RQ) and revealed that the risk of difenoconazole with seven interval days and chlorothalonil with twenty-one interval days in leafy vegetables was acceptable. The pre-harvest intervals (PHIs) were recommended of seven days for difenoconazole and twenty-one days for chlorothalonil in leafy vegetables. The study contributes to a better understanding of the potential risks of fungicides in leafy vegetables.