Assessing Agrochemical Risk to Mated Honey Bee Queens

Summary

This protocol was developed to enhance the understanding of how agrochemicals affect honey bee (Apis mellifera) reproduction by establishing methods to expose honey bee queens and their worker caretakers to agrochemicals in a controlled, laboratory setting and carefully monitoring their relevant responses.

Abstract

Current risk assessment strategies for honey bees rely heavily upon laboratory tests performed on adult or immature worker bees, but these methods may not accurately capture the effects of agrochemical exposure on honey bee queens. As the sole producer of fertilized eggs inside a honeybee colony, the queen is arguably the most important single member of a functioning colony unit. Therefore, understanding how agrochemicals affect queen health and productivity should be considered a critical aspect of pesticide risk assessment. Here, an adapted method is presented to expose honey bee queens and worker queen attendants to agrochemical stressors administered through a worker diet, followed by tracking egg production in the laboratory and assessing first instar eclosion using a specialized cage, referred to as a Queen Monitoring Cage. To illustrate the method's intended use, results of an experiment in which worker queen attendants were fed diet containing sublethal doses of imidacloprid and effects on queens were monitored are described.

Introduction

Due to increased global demand for agricultural products, modern farming practices often require the use of agrochemicals to control numerous pests known to reduce or harm crop yields¹. Simultaneously, the growers of many fruit, vegetable, and nut crops rely on the pollination services provided by commercial honey bee colonies to ensure abundant crop yields². These practices may result in pollinators, including honey bees (Apis mellifera), being exposed to harmful levels of pesticide residues³. At the same time, the widespread presence of parasitic Varroa destructor mite infestat....

Protocol

1. QMC assembly

1. Assemble QMCs from parts (Figure 1A) with a single egg laying plate (ELP) inserted as shown in Figure 1B. Do not add feeder tubes until after the workers have been added to the cage. Temporarily cover the 4 feeder holes with laboratory grade tape.
2. Insert the queen excluder and the feeding chamber door over the feeding chamber to keep the queen from entering the feeding chamber and contacting the treated diet. See Fine et al.³² for further assembly details.
3. Collect the wax comb frames containing the capped worker brood from honeybee coloni....

Results

The production of eggs was monitored in QMCs assembled and maintained as described above with once daily observations of egg production and 15 cages per treatment group. Newly mated queens of primarily Carniolan stock were purchased and shipped overnight from a queen breeder, and honey bee workers were obtained from 3 colonies maintained according to standard commercial methods at The Bee Research Facility at the University of Illinois Urbana-Champaign. Here, 4 dietary treatment groups were used: 1) 50 ppb (g/g) imidaclo.......

Discussion

The fecundity of female solitary insects as well as queens in eusocial insect colonies can be influenced by abiotic stressors such as agrochemicals^{25,28,29,30,33}. In honey bees, the effects of agrochemicals on queens may be indirect, as they can occur via changes in their care and feeding by worker bees. Our representative results, which are similar to those r.......

Materials

Name	Company	Catalog Number	Comments
Fluon	BioQuip, Rancho Dominguez, CA	2871A
Honey bee queens	Olivarez Honey Bees, Orland, CA
Imidacloprid	Sigma-Aldritch, St. Louis, MO	37894
MegaBee Powder	MegaBee, San Dieago, CA
Microcentrifuge tubes 2 mL	ThermoFisher Scientific, Waltham, MA	02-682-004
Needles 20 gauge	W. W. Grainger, Lake Forest, IL	5FVK4
Potassium Sulfate	Sigma-Aldritch, St. Louis, MO	P0772
Queen Monitoring Cages	University of Illinois Urbana-Champaign		Patent application number: 20190350175
Sucrose	Sigma-Aldritch, St. Louis, MO	S8501
Universal Microplate Lids	ThermoFisher Scientific, Waltham, MA	5500