Residue extrapolation and group maximum residue level recommendation for four pesticides in the four kinds of vegetable crop groups

The residue behaviours of difenoconazole, bifenthrin, thiamethoxam and its metabolite clothianidin on representative crops such as cucumber, bitter gourd, loofah, zucchini, tomato, cherry tomato, eggplant, cowpea, kidney bean, celery, and fennel were investigated. The effects of factors such as fruit size, property of epidermis, leaf size and others on pesticide residues were studied, and then analysed whether these crops are suitable for the same group. Results indicated residue extrapolation could be made between the different crop groups or subgroups. It could be extrapolated from high-risk residue crops to the low-risk residue crops. Cherry tomato or eggplant could be extrapolated to tomato, and bitter gourd or loofah could be extrapolated to cucumber or zucchini, and the reverse was unacceptable. For these four vegetable groups, the different edible parts led to a significant difference in pesticide residues, celery and fennel had higher residue risk because the edible parts were whole plants including the leaves. The residue difference in the same edible parts of the different crop groups was not obvious, such as the Fruiting vegetables, Cucurbits group and the Fruiting vegetables, other than Cucurbit group. The processing factor (PF) extrapolation was more reasonable because crop varieties had no significant effect on pesticide residues in processed commodities. From the perspective of pesticide residues, representative crops were proposed and the rationality of crop classification and residue extrapolation was analysed. These results could promote the process of pesticide registration and the settlement of Maximum Residue Limit (MRL) standards, and further solve the missing of MRL for minor crops.