Proposed Generic Conceptual Models 

of Pesticide Exposure and Effects to

Honey Bees

U.S. Environmental Protection Agency 1

Keith Sappington, M.S.

Environmental Fate and Effects Division

Office of Pesticide Programs
Outline

Introduction

• Background and utility of CMs

• Purpose of generic CMs for 

honey bees

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Planning

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Integrate Available Information

Source & Ecosystem Ecological

Exposure at Risk Effects

Assessment Conceptual

Problem Formulation

Generic conceptual models

• Foliar spray applications (nonsystemic and systemic)

• Soil applications

• Seed treatment

Planning

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Assessment

Endpoints

Analysis

Plan

Conceptual

Model

Analysis
Introduction

• A conceptual model is a written and visual description of the 

predicted relationships between ecological entities and the 

stressors of concern (USEPA 1998).

Risk hypotheses

Conceptual diagram

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Conceptual diagram

• Useful tool for communicating the predicted pathways of 

exposure and effects in relation to assessment endpoints

• Vary from simple to complex and in graphical format

• General structure: 

Source Exposure  Receptor/Response Attribute 

Change
Generic Conceptual Models for Honey Bees 

• Intended as a “starting point” for pesticide risk assessors; to be 

modified where appropriate

• Represent major pesticide uses that may result in significant 

exposure to honey bees 

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exposure to honey bees 

(foliar, soil, seed treatment, trunk [drench] / injection)

• Reflect differences in pesticide use patterns and chemical 

characteristics (systemicity) 
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Stressor

Source

Non-Systemic Pesticide: Foliar Spray Application

Exposure 

Media 

Dermal Uptake &

Inhalation

Ingestion

Deposition onto 

Plants

Spray Deposition 

On Bees

Deposition onto 

Soil

Deposition onto 

Surface Water

Residues On 

Plant Surfaces

Residues On 

Pollen & 

Nectar 

Residues in 

Soil

Residues in 

Surface Water

Runoff/ 

Erosion

Attribute 

Change 

(assessment 

endpoint)

Receptors

Foraging Bees (workers)

Inhalation

* Brood initially rely on brood jelly and royal jelly, but later in development consume processed pollen and honey; whereas queens rely solely on 

royal jelly. 

** interception of spray droplets is also a potential route of exposure during mating and orientation flights

Population Size and Stability of Colonies

Reduced colony strength and survival

Reduced queen fecundity & brood success

Reduced individual survival, behavior changes

Quantity and Quality of Hive Products

Reduced honey, wax, propolis production

Contribution to Pollinator Biodiversity

Reduced species richness and abundance 

Hive Bees (Nurse, 

Worker, Drone**)

Pollen & Nectar, Processing, 

Ingestion; Comb Production

Bee Brood 

Queen**

Brood provisions*

Royal Jelly

Wax, Propolis
Stressor

Source

Systemic Pesticide: Foliar Spray Application

Exposure 

Media 

Dermal Uptake &

Inhalation

Residues On 

Plant Surfaces

Deposition onto 

Plants

Residues In (On) 

Pollen, Nectar, 

Exudates, Honey 

Dew

Spray Deposition 

On Bees

Deposition onto 

Soil

Residues In 

Soil

Ingestion

Deposition onto 

Surface Water

Residues in 

Surface 

Water

Root 

Uptake

Runoff/ 

Erosion Foliar Translocation

Foraging Bees (workers) Hive Bees (Nurse, 

Receptors Worker, Drone**)

Inhalation

Bee Brood 

Queen**

Pollen & Nectar Processing, 

Ingestion; Comb Production

Brood Provisions*

Royal Jelly

Population Size and Stability of Colonies

Reduced colony strength and survival

Reduced queen fecundity & brood success

Reduced individual survival, behavior changes

Quantity and Quality of Hive Products

Reduced honey, wax, propolis production

Contribution to Pollinator Biodiversity

Reduced species richness and abundance 

* Brood initially rely on brood jelly and royal jelly, but later in development consume processed pollen and honey; whereas queens rely solely on 

royal jelly. 

** interception of spray droplets is also a potential route of exposure during mating and orientation flights

Wax, Propolis

Attribute 

Change 

(assessment 

endpoint)
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Stressor

Source

Systemic Pesticide: Soil Application

Exposure 

Media 

Residues in Soil*

Residues In 

Pollen, Nectar, 

Exudates

Ingestion

Root Uptake

Residues in 

Surface Water

Runoff/ 

Erosion

Foraging Bees (workers) Hive Bees (Nurse, 

Receptors Worker, Drone)

Bee Brood 

Queen Pollen & Nectar Processing, 

Ingestion; Comb Production

Brood Provisions**

Royal Jelly

* For spray applications to soil, exposure of bees via off site drift of pesticide would be addressed as illustrated for foliar spray applications, accounting for the 

amount of pesticide drift. ** Brood initially rely on brood jelly and royal jelly, but later in development consume processed pollen and honey; whereas 

queens rely solely on royal jelly. 

Population Size and Stability of Colonies

Reduced colony strength and survival

Reduced queen fecundity & brood success

Reduced individual survival, behavior changes

Quantity and Quality of Hive Products

Reduced honey, wax, propolis production

Contribution to Pollinator Biodiversity

Reduced species richness and abundance 

Wax, Propolis

Attribute 

Change 

(assessment 

endpoint)
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Stressor

Source

Systemic Pesticide: Seed Treatment

Exposure 

Media 

Dermal Uptake 

& Inhalation

Deposition onto 

soils, plants, 

surface water

Residues on 

Planted Seeds

Residues In 

Pollen, Nectar , 

Exudates, Honey 

Dew

Root Uptake

Drift of Abraded 

Seed Coating

Foliar

Translocation

Seed-based Translocation

Foraging Bees (workers) Hive Bees (Nurse, 

Receptors Worker, Drone**)

Bee Brood 

Queen** Pollen & Nectar Processing, 

Ingestion; Comb Production

Brood Provisions*

Royal Jelly

Population Size and Stability of Colonies

Reduced colony strength and survival

Reduced queen fecundity & brood success

Reduced individual survival, behavior changes

Quantity and Quality of Hive Products

Reduced honey, wax, propolis production

Contribution to Pollinator Biodiversity

Reduced species richness and abundance 

* Brood initially rely on brood jelly and royal jelly, but later in development consume processed pollen and honey; whereas queens rely solely on royal jelly. 

** interception of dust particles is also a potential route of exposure during mating and orientation flights

Wax, Propolis

Attribute 

Change 

(assessment 

endpoint)
Summary

• Honey bee generic conceptual models are intended to reflect 

some major pesticide uses and to serve as a starting point for risk 

assessors to consider in Problem Formulation. 

• They should be modified where appropriate

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• They should be modified where appropriate

• EPA is seeking feedback on these generic conceptual model 

accuracy and their consistency with the proposed assessment 

endpoints and management goals (Charge Question 2).