To clarify the residue characteristics of the novel acaricides cyetpyrafen in different parts of Malus domestica.
Field trials were conducted in accordance with the Guidelines for pesticide residue trials in crops. The 30% cyetpyrafen suspension was used as the test object, and the early-maturing Malus domestica variety Honglu was used as the test material. The whole Malus domestica trees were sprayed with the recommended dose and twice the recommended dose during the occurrence period of Malus domestica mites and before fruit harvest. Samples were randomly collected after spraying. The residues of cyetpyrafen in different parts of Malus domestica at different doses were determined by QuEChERS-high performance liquid chromatography.
Within the mass concentration range of 0.05–5.00 mg/L, the mass concentration of cyetpyrafen in the Malus domestica matrix had a good linear relationship with the response value, and the correlation coefficient was greater than 0.99. In the addition recovery test, the average recovery rate of cyetpyrafen was 98.88%–100.22%(relative standard deviation was 0.34%–0.92%). The detection results showed that the residues of cyetpyrafen mainly adhered to the Malus domestica peel, and the residues conducted to the flesh through internal absorption were very few. The average residue amount showed the trend of peel>whole fruit>flesh. Under the recommended dosage, the residue level in the fruit peel was the highest, reaching 3.19 mg/kg 2 h after application, which was over 3 times the maximum residue limit (MRL) (1 mg/kg). The residue level in the fruit peel dropped to 0.6 mg/kg 5 d after application, below the MRL (1.00 mg/kg), indicating a relatively low safety risk. At twice the recommended dose, the original residue amount in the peel 2 h after spraying was 5.90 mg/kg, which was 1.85 times that of the recommended dose. At twice the recommended dose, the residue amount in the peel 7 d after spraying was 1.11 mg/kg>1.00 mg/kg(MRL), still not meeting the standard.
The Malus domestica peel is the main residue site of etofenprox.The residue amount increases significantly with the increase of the application dose. Applying at doses exceeding the recommended level will significantly increase the residue risk and directly affect the food safety of Malus domestica.It is recommended that during production, the recommended dosage should be strictly followed for application, and the frequency of application should be controlled. It is suggested that a harvest interval of more than 7 d. Consumers can effectively reduce potential risks by peeling the fruit.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |