Neonicotinoid contamination in wildflowers collected from citrus orchards in a northwestern Mediterranean Region (Spain) after tree foliar treatments
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Ground-cover vegetation attracts and harbors benefcial insects to the agrosystem, playing an important role in conserva tion biological control. Integrated pest management (IPM) program guidelines recommend the implantation of sowed or resident wild covers in perennial crops. Given the high-quality fruit requirements, even in IPM programs, insecticides can be required in citrus crops. This study presents, over a year, the levels of neonicotinoids (thiamethoxam and imidacloprid) in not-target ground-cover wildfowers growing spontaneously in citrus orchards after foliar treatment of citrus trees. The pres ence and persistence of these neonicotinoids in diferent wildfower species were studied. Concentrations of thiamethoxam and imidacloprid in whole wildfowers ranged from<method quantifcation limit (MQL) to 52.9 ng g−1 and from<MQL to 98.6 ng g−1, respectively. Thiamethoxam was more frequently detected than imidacloprid. Thiamethoxam and imidacloprid were detected up to 336 and 230 days after treatment, respectively. The highest detection frequencies (100%) and highest thiamethoxam and imidacloprid mean concentrations (26.0±7.3 ng g−1 and 11.0±10.6 ng g−1, respectively) occurred in wildfowers collected 9 days after the treatments. Since application, a clear decrease in the concentration of both compounds and diferences in the accumulation depending on wildfower species were observed. Cross contamination was detected, indicating a transport from adjacent treated plots. Maintaining a cover crop in citrus orchards may lead to detrimental efects on non-target arthropods if these neonicotinoid compounds are used for pest control since they can entail a chronic exposure during at least 230 days for imidacloprid and 336 days for thiamethoxam.