The FX of Neonics

What are the lethal and sub-lethal effects of neonicotinoid insecticides on bees?

Updated July 13, 2019

Neonicotinoids are the most widely used class of insecticides. They attack an insect’s central nervous system, causing paralysis and death. While most uses aren’t intended to kill bees, research shows that significant incidental harm can occur; even at sublethal exposure, neonicotinoids can damage a bee’s ability to communicate, smell, navigate and simply move its body. Here’s what we currently know about the impact of neonics on bees, based on a recent review of the scientific literature on this topic.

Pie chart showing the nine categories of impacts of neonicotinoids indetified in the research.

After reviewing the literature, the specific effects in a study were each grouped into one of nine different categories. As you can see above, Reproduction is the category of impact most commonly documented. However, this could simply be the result of the number of studies looking at that particular outcome. And Reproduction, like all the categories, covers a range of specific effects. The tables below provide a look at the specific effects within each category.

BEHAVIORS

EffectChangeBeesNeonicsReferences
bee immobility IMMoffat et al. 2016
breathingIMHatjina et al. 2013
feedingTHElston et al. 2013
hygienic behaviorIMTsvetkov et al. 2017; Wu-Smart & Spivak 2016
locomotor skills in queensIMWu-Smart & Spivak 2016
motor functionCL, DN, IMWilliamson et al. 2014
pollination servicesTHStanley et al. 2015b
proboscis extensionAC, THAlkassab & Kirchner 2016; D̩mares et al. 2016; Thany et al. 2015
swarmingCL&THSandrock et al. 2014a
time groomingTHWilliamson et al. 2014
worker movementCL, IM, THScholer & Krischik 2014

COGNITION

EffectChangeBeesNeonicsReferences
learningTHStanley et al. 2015a
memory, long-term CL, IMAlkassab & Kirchner 2016; Williamson & Wright 2013
memory, short-term and mid-term IM, THStanley et al. 2015a; Williamson & Wright 2013

FORAGING

EffectChangeBeesNeonicsReferences
foraging activityCLArce et al. 2016; Wu-Smart et al. 2016
flight duration (chronic exposure)THTosi et al. 2017
flight duration (acute exposure)THTosi et al. 2017
flight distance (chronic exposure)THTosi et al. 2017
flight distance (acute exposure)THTosi et al. 2017
flight velocityTHTosi et al. 2017
forager recruitmentIMGill et al. 2012
foraging performanceIMCresswell 2011
foragers returning to patchIMKarahan et al. 2015
foraging tripsIMKarahan et al. 2015
homing capacityCL, IM, THFischer et al. 2014; Yang et al. 2012
pollen loadIMGill et al. 2012; Stanley et al. 2016
pollen storesIMWu-Smart & Spivak 2016
pollen trip (duration)IMGill et al. 2012
pollen trip (successful)IMGill et al. 2012
rate of return to colonyTHStanley et al. 2016
time spent foragingTHStanley et al. 2016
workers lost during foragingIMGill et al. 2012

LIFE SPAN

EffectChangeBeesNeonicsReferences
daily mortalityIMAbbo et al. 2017
life spanCLStraub et al. 2016; Tsvetkov et al. 2017
mortalityIMAlaux et al. 2010; Trayner et al. 2016
mortality (synergistic effects)CL, THSgolastra et al. 2016; Zhu et al. 2017
worker mortalityIM, THMommaerts et al. 2010

PARASITES, PATHOGENS, DISEASE

EffectChangeBeesNeonicsReferences
parasites and pathogens (abundance)variousSanchez-Bayo et al. 2016
parasites and pathogens (spread)variousSanchez-Bayo et al. 2016
immune responseIMCzerwinski & Sadd 2017
varroa infestationCL&THAlburaki et al. 2015; Alburaki et al. 2018

PHYSIOLOGY

EffectChangeBeesNeonicsReferences
body massIMAbbo et al. 2017
depolarization in neuronsIMMoffat et al. 2015
gene expression (variety of genes)AC, CL, IM, THChristen et al. 2016; Simmons & Angelini 2017
hemocyte countCLBrandt et al. 2016; Hernandez-Lopez et al. 2017
neural stimulationCL, IMMoffat et al. 2016
neural sensitivity to substancesIMMoffat et al. 2015
size of hypopharyngeal glandsIMAlaux et al. 2010; Hatjina et al. 2013
thermoregulationTHTosi et al. 2016
vitellogenin levelsIMAbbo et al. 2017

POPULATIONS

EffectChangeBeesNeonicsReferences
wild bee densityCLRundlöf et al. 2015

REPRODUCTION

EffectChangeBeesNeonicsReferences
reproductionCLRundlöf et al. 2015
reproductive successCL&THWilliams et al. 2015
adult workers, drones, gynes numbersCLArce et al. 2016
brood cellsIM, TH, CL&THMoffat et al. 2016; Sandrock et al. 2014b
brood developmentIMGill et al. 2012
brood productionIMWu-Smart & Spivak 2016
brood sizeCL&THSandrock et al. 2014a
colony failureTCEllis et al. 2017
colony growthCL, IMBryden et al. 2013; Rundlöf et al. 2015
colony survivalIMTasei et al. 2000
colony weightTCEllis et al. 2017
completed nestsCL&THSandrock et al. 2014b
dead coloniesCL&THAlburaki et al. 2015; Alburaki et al. 2018
dronesIMMommaerts et al. 2010; Woodcock et al. 2017
drone productionIM, THMommaerts et al. 2010
egg cellsCL, THWoodcock et al. 2017
eggs laidIM, THElston et al. 2013; Wu-Smart & Spivak 2016
femalesTHMoffat et al. 2016
females (proportion to offspring)CL&THSandrock et al. 2014b
larva producedTHElston et al. 2013
larval moralityCLHernandez-Lopez et al. 2017
likeliness to loose queenAC, CL, IM, THTsvetkov et al. 2017
nest buildingTHElston et al. 2013
nest reproductionIMMommaerts et al. 2010
offspring able to hatchCL&THSandrock et al. 2014b
offspring completing developmentCL&THSandrock et al. 2014b
offspring productionCL&THSandrock et al. 2014b
ovary sizeCL&THWilliams et al. 2015
population size of adultsCL&THSandrock et al. 2014a
queens laying eggs (percentage)CL&THWilliams et al. 2015
queen productionCL, IM, TH, IM&THMoffat et al. 2016; Whitehorn et al. 2012; Woodcock et al. 2017
queen replacementCL&THSandrock et al. 2014a
queen survivalCL, IMFauser et al 2017; Scholer & Krischik 2014
reproductive cellsCL, IM&THWoodcock et al. 2017
reproductive individualsTCEllis et al. 2017
solitary bee nestingCLRundlöf et al. 2015
sperm qualityCL&THWilliams et al. 2015
sperm viabilityCL, THStraub et al. 2016
storage cellsCL, THWoodcock et al. 2017
time of developmentCL&THAbbot et al. 2008
wax cells builtTHElston et al. 2013
worker fecundityIMLaycock et al. 2012
workersCLWoodcock et al. 2017
workers producedTHStanley et al. 2016

SENSORY

EffectChangeBeesNeonicsReferences
olfactory associative behaviorIMYang et al. 2012

Methodology

This review is based predominately on two sources of information:

1. Supplementary materials from Mitchell and colleagues’ 2017 study, “A worldwide survey of neonicotinoids in honey”. Table S8 in those materials contains an extensive list of effects and references to the studies demonstrating each effect.

Mitchell, E. A. D., B. Mulhauser, M. Mulot, A. Mutabazi, G. Glauser, and A. Aebi. 2017. “A Worldwide Survey of Neonicotinoids in Honey.” Science, October, 109–11.

2. The IPI database which contains summaries of research articles on pesticides and their effects on invertebrates. The articles in the database have been reviewed and summarized by Xerces Society staff. This list was built from the results of a search for “neonicotinoids, bees”.

Effect: The impact descriptions were taken from the summaries of research in the supplemental materials and the IPI database. When necessary, I referred to the abstracts of the original research work for clarification. In listing the effects and grouping together different studies with similar effects, I was particularly careful not to combine effects that could be subtly but distinctly different (ex. decreases in “nest building” and “nest reproduction” are not necessarily the same thing); I preferred to risk duplicating effects on the list rather than miss an important distinction between them. In the interest of making the list easier to navigate and read, I grouped together effects into different categories that seemed to make sense.

Type of Change: The direction of each impact – “decrease” or “increase” – was also taken from the summaries of research in the supplemental materials and IPI database. When both “decrease” and “increase” are listed, it indicates mixed results within a single study or between studies. “Altered” is my own category for results that did not seem best represented by “decrease” or “increase” or both.

Type of Bees: The category “Honey bees” includes Apis mellifera. “Bumble bees” includes Bombus terrestris and Bombus impatiens. “Solitary bees” includes Osmia bicornis with a single occurrence of Osmia lignaria.

This project is on-going. If you have additional research that you believe should be included in the review, please get in touch with me [link to contact page].