Tracking Pesticide Residues to a Plant Genus Using Palynology in Pollen Trapped from Honey Bees (Hymenoptera: Apidae) at Ornamental Plant Nurseries

Abstract

Worldwide studies have used the technique of pollen trapping, collecting pollen loads from returning honey bee ( Apis mellifera L.) (Hymenoptera: Apidae) foragers, to evaluate the exposure of honey bees to pesticides through pollen and as a biomonitoring tool. Typically, these surveys have found frequent contamination of pollen with multiple pesticides, with most of the estimated risk of acute oral toxicity to honey bees coming from insecticides. In our survey of pesticides in trapped pollen from three commercial ornamental plant nurseries in Connecticut, we found most samples within the range of acute toxicity in a previous state pollen survey, but a few samples at one nursery with unusually high acute oral toxicity. Using visual sorting by color of the pollen pellets collected in two samples from this nursery, followed by pesticide analysis of the sorted pollen and palynology to identify the plant sources of the pollen with the greatest acute toxicity of pesticide residues, we were able to associate pollen from the plant genus Spiraea L. (Rosales: Rosaceae) with extraordinarily high concentrations of thiamethoxam and clothianidin, and also with high concentrations of acephate and its metabolite methamidophos. This study is the first to trace highly toxic pollen collected by honey bees to a single plant genus. This method of tracking high toxicity pollen samples back to potential source plants could identify additional high-risk combinations of pesticide application methods and timing, movement into pollen, and attractiveness to bees that would be difficult to identify through modeling each of the contributing factors.

A screening-level assessment of the pollinator-attractiveness of ornamental nursery stock using a honey bee foraging assay

“…(2020) 10:831 | https://doi.org/10.1038/s41598-020-57858-2 www.nature.com/scientificreports www.nature.com/scientificreports/ Methods Study sites and sampling regime. The current study used samples that were previously analyzed for pesticide residues and reported in 38 . The study sites and pollen sampling scheme are described in detail in 38 , and briefly described here.…”

“…The current study used samples that were previously analyzed for pesticide residues and reported in 38 . The study sites and pollen sampling scheme are described in detail in 38 , and briefly described here.…”

“…Thirty-one of our 47 samples were cross-validated by microscopy to provide a second line of evidence for inferring the role of ornamental plants in the honey bee pollen diet. Pollen microscopy was performed at the Paleoecology Laboratory, Climate Change Institute, University of Maine, Orono, Maine, as described in 38 . Bulk corbicular pollen samples (0.47-0.85 g) were first granularized in 10% hydrochloric acid, washed in deionized water to remove excess organics, and then rinsed in glacial acetic acid to remove all water.…”

The use of the Hazard Quotient approach to assess the potential risk to honeybees (Apis mellifera) posed by pesticide residues detected in bee‐relevant matrices is not appropriate

“…The majority of papers have attempted to address this by translating the HQ threshold into a percentage of the LD 50 based on daily consumption of pollen, e.g. a HQ of 50, 100 or 1000 corresponding to 0.05%, 0.1% or 1% of the acute oral LD 50 , respectively, 6–9 but provide no evidence to support the importance of the cited percentage of the acute oral LD 50 . Taking this further, the percentage of the acute (single dose) LD 50 represented by the HQ has been increased ten‐fold by using estimates of cumulative pollen consumption by nurse bees over a 10‐day period, i.e.…”

Pesticide contamination of milkweeds across the agricultural, urban, and open spaces of low elevation Northern California

“…One strength of these data is their standardized collection and thus ease of use for comparison across compounds in examining collective (or additive) effects. To do this, we calculated the hazard quotient for each compound, by dividing the detected concentration by the LD 50 , and then summed this across all compounds in each sample (Stoner et al, 2019). This approach has an important drawback in that assumes a linear relationship between concentration and effect, which is often not realized, and then propagates this across all compounds in each sample.…”