Summary
This article measured uptake and dissipation of soil-applied imidacloprid and dinotefuran in nectar and leaves of 2
woody plant species, a broadleaf evergreen tree and a deciduous shrub, to assess concentrations to which pollinators and pests might be exposed in landscape settings.
Imidacloprid and Thiamethoxam are the largest selling insecticides in the world. Dr. Stoner and Dr. Eitzer studied the movement of these systemic insecticides throughout squash plants to determine the concentration of the insecticide in the fully developed plant, nectar, and pollen. The squash was treated two ways: by spraying the insecticide into the soil before seeding and applied through drip irrigation in a single treatment after transplant. The study found that the entire plant had a higher concentration of insecticides than just the flowers, nectar, or pollen. The results found concentrations of 10 ±3 for Imidacloprid and 11±6 ppb of Thiamethoxam in nectar and 14±8 ppb of Imidacloprid and 12±9 ppb Thiamethoxam in pollen. The concentration found in the squash fell into the range of what is being investigated in the range of what is believed to be sub-lethal for bees.
Abstract
Systemic neonicotinoid insecticides used in urban arboriculture could pose a risk to bees and other pollinators foraging
on treated plants. We measured uptake and dissipation of soil-applied imidacloprid and dinotefuran in nectar and leaves of 2 woody plant species, a broadleaf evergreen tree (Ilex X attenuata) and a deciduous shrub (Clethra alnifolia), to assess
concentrations to which pollinators and pests might be exposed in landscape settings. Three application timings, autumn
(postbloom), spring (prebloom), and summer (early postbloom), were evaluated to see if taking advantage of differences in the neonicotinoids’ systemic mobility and persistence might enable pest control while minimizing transference into nectar. Nectar and tissue samples were collected fromin-ground plants and analyzed for residues by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) in 2 successive years. Concentrations found in nectar following autumn or spring applications ranged from 166 to 515 ng/g for imidacloprid and from 70 to 1235 ng/g for dinotefuran, depending on plant and timing. These residues exceed concentrations shown to adversely affect individual- and colony-level traits of bees. Summer application mitigated concentrations of imidacloprid (8–31 ng/g), but not dinotefuran (235–1191 ng/g), in nectar. Our data suggest that dinotefuran may be more persistent than is generally believed. Implications for integrated pest and pollinator management in urban landscapes are discussed.
