Original deposition behavior and influencing factors of imidacloprid and acetamiprid residues on two leafy vegetables

The original deposition behavior of pesticides on leafy vegetables is an important index to evaluate pesticide residues, which is affected by crop morphology, pesticide and formulation type, application method and so on. Taking imidacloprid and acetamiprid as the target pesticides and spinach and lettuce as the target crops, the original deposition behavior of pesticides after application, as well as the effects of water content, leaf area index and pesticide formulation type on pesticide deposition were studied to reveal the original deposition law of pesticides on leafy vegetables. The results showed that there were no significant difference in the deposition amount of two pesticides within 0.5-8 h after application. In a comprehensive consideration, the original deposition amount was determined at 2 h after the application of the pesticides. The results showed that imidacloprid and acetamiprid were mainly deposited on the leaves of spinach and lettuce, accounting for more than 87% of total, and was much less in the root and soil. The original deposition amount of the two pesticides on spinach and lettuce had significant difference with different water dosages (at the same pesticide dosages). The original deposition amount of the two pesticides decreased gradually with the increase of water dosage. The deposition amount of two pesticides on spinach and lettuce were negatively correlated with leaf area index. The type of formulation of pesticides was also related to the original deposition amount. At the same pesticide dosage, imidacloprid in wettable powder had the highest original deposition in spinach and lettuce, with the deposition amounts of 0.66 and 0.77 mg/kg, respectively. The highest original deposition amount of acetamiprid in spinach was emulsifiable concentrate and wettable powder, with a deposition amount of 0.65 mg/kg. The highest original deposition amount of acetamiprid in lettuce was wettable powder, with a deposition amount of 0.37 mg/kg. The results indicated that the original deposition amount of pesticides on the surface of leafy vegetables was related to the types of pesticide formulation, water dosage and leaf area index. The finding could provide theoretical support for the rational and safe application of pesticides and the control of pesticide residues in leafy vegetables.