WVU Extension and Division of Plant and Soil Science, West Virginia University, Morgantown, WV, 26506, USA.
Entomology and Nematology Department, University of Florida, Gainesville, FL, 32611, USA.
Environ Pollut. 2023 Nov 15;337:122527. doi: 10.1016/j.envpol.2023.122527. Epub 2023 Sep 10.
Whiteflies are important insect pests in a wide variety of agricultural crops that are targeted with large quantities of insecticides on a global scale. Chemical control is the most common strategy to manage whiteflies, however, recent studies had reported that whiteflies and other hemipterans can excrete insecticides through their honeydew, which could have unanticipated, non-target effects. The objective of this study was to determine the concentration of imidacloprid in honeydew excreted by whiteflies feeding on tomato plants. Imidacloprid was applied at its labeled rate to soil at the base of whitefly-infested plants. Densities of whiteflies were assessed before insecticide treatment and 21 days after treatment (DAT). Honeydew was collected in Petri dishes from 1 to 4 DAT and from 5 to 8 DAT. The volume of the honeydew was calculated using stereo microscopy and then rinsed with ethanol. The rinsates were analyzed to determine imidacloprid concentration using liquid chromatography coupled to mass spectrometry. Honeydew production was further quantified by using water sensitive papers. Imidacloprid reduced densities of nymph and adult whiteflies by 81.5% and 76.0% compared to the control at 21DAT. The non-metabolized parent compound imidacloprid was detected from honeydew samples at both collection dates. At 1-4 DAT, imidacloprid concentrations were 180 ng/30 mL in a volume of 39 mm of honeydew. At 5-8 DAT, the imidacloprid concentration was 218 ng/30 mL in a volume of 25 mm of honeydew. Though the volume of honeydew decreased, the concentration of imidacloprid numerically increased. Last, whiteflies were still producing honeydew 22 DAT in both treatments. These results revealing significant imidacloprid concentrations in honeydew suggest a strong potential for negative secondary impacts on beneficial insects.
粉虱是广泛种植的农业作物中的重要害虫，全球范围内大量使用杀虫剂进行防治。化学防治是管理粉虱的最常见策略，但最近的研究报告称，粉虱和其他半翅目昆虫可以通过蜜露将杀虫剂排出体外，这可能会产生意想不到的非靶标效应。本研究的目的是确定取食番茄植株的粉虱所排泄蜜露中的吡虫啉浓度。吡虫啉按标签推荐剂量施用于粉虱为害植株的根部土壤。在施药前和施药后 21 天（DAT）评估粉虱密度。在 1 至 4 DAT 和 5 至 8 DAT 时，从每只粉虱取食的培养皿中收集蜜露。使用立体显微镜计算蜜露的体积，然后用乙醇冲洗。用高效液相色谱-串联质谱法分析冲洗液以确定吡虫啉浓度。进一步通过使用水敏纸定量测定蜜露产量。与对照相比，21 DAT 时，吡虫啉处理组的若虫和成虫粉虱密度分别降低了 81.5%和 76.0%。在两个采集日期均从蜜露样品中检测到非代谢母体化合物吡虫啉。在 1-4 DAT 时，39mm 体积的蜜露中吡虫啉浓度为 180ng/30mL。在 5-8 DAT 时，25mm 体积的蜜露中吡虫啉浓度为 218ng/30mL。尽管蜜露体积减少，但吡虫啉浓度数值增加。最后，两种处理组的粉虱在 22 DAT 时仍在产生蜜露。这些结果表明蜜露中存在显著浓度的吡虫啉，表明其对有益昆虫具有潜在的强烈负向二次影响。
