# What’s in a pollen provision? Using larval provisions to quantify pesticide exposure in Megachile rotundata (Hymenoptera: Megachilidae)

## TL;DR

This study analyzes pesticide residues in food provisions for leafcutting bee larvae to assess their exposure and potential risks in agricultural areas.

## Contribution

The study provides the first regional profile of pesticide exposure for Megachile rotundata in southern Alberta using larval provisions.

## Key findings

- Eight pesticide residues were detected across three classes in larval provisions from nine sites.
- Sites with multiple pesticide classes had higher hazard quotients compared to sites with single-class residues.
- The findings highlight compounds of concern for future toxicological testing and pollinator management.

## Abstract

The alfalfa leafcutting bee (LCB) (Megachile rotundata Fabricius) is a solitary, managed pollinator widely used in North American agriculture to produce alfalfa and hybrid canola seed. Despite its economic importance, and known sensitivity to certain pesticides, little is known about the specific pesticide residues LCBs encounter during pollination, and toxicity data for this species remains limited. To determine what residues LCBs are commonly exposed to, we screened larval LCB provisions from nine alfalfa sites during pollination in southern Alberta for 69 pesticide residues. Eight residues amongst three classes of pesticides were detected including four fungicides (boscalid, cyprodinil, fludioxonil, and pyraclostrobin), three insecticides (chlorpyrifos, cyhalothrin lambda, and deltamethrin), and the herbicide Velpar (hexazinone). Using the residue data, we calculated site-specific hazard quotients (HQ) using Apis mellifera L. LD50s to provide context for exposure risk. Sites with residues from multiple pesticide classes tended to have higher—though not always significantly higher—HQs than sites with residues from only one class. These findings provide a regional profile for pesticide exposure for LCBs in southern Alberta and identifies compounds of potential concern for future toxicological testing and pollinator management.

Graphical Abstract