Robots reveal: commonly used pesticides harm bee behavior and metabolism

Scientists, automated robots, and mini-backpacks equipped with tiny QR codes team up to finally understand how pesticides harm the lives of bees. Read the full scientific article here and check out the lead author’s, James Crall’s, website for details and more awesome video.

Crall JD, Switzer CM, Oppenheimer RL, Ford Versypt A, Dey B, Brown B, Eyster M, Guérin C, Pierce NE, Combes SA, de Bivort BL (2018).  Neonicotinoid exposure disrupts bumblebee nest behavior, social networks, and thermoregulationScience 362, 683–686. PDF

Photo by James Crawl: Bumblebee  (Bombus impatiens)  wearing a simplified QR code for individual recognition and tracking

Photo by James Crawl: Bumblebee (Bombus impatiens) wearing a simplified QR code for individual recognition and tracking

 

Neonicotinoid pesticides are widely used to protect our crops from insect pests, but neonicotinoids don’t discriminate, as they also target beneficial insects like pollinating bees. This class of pesticides disrupts an animal’s nervous system affecting their behaviors and physiology.

USDA estimated annual imidacloprid use in the US for 2016.

USDA estimated annual imidacloprid use in the US for 2016.

 

The neonicotinoid imidacloprid is applied to an estimated 1 million pounds of vegetables, fruit, and soy annually in the US, and the pesticide can remain in plant tissue for up to 230 days after application.

USDA estimated annual imidacloprid use by crop in the US, 2016. Celebrate in that the total estimated annual imidacloprid use has decreased by 1 million pounds of food in recent years.

USDA estimated annual imidacloprid use by crop in the US, 2016. Celebrate in that the total estimated annual imidacloprid use has decreased by 1 million pounds of food in recent years.

Harvard scientists developed an automated robot to continuously track the behavior of bees to characterize the negative effects of eating ecologically relevant levels of imidacloprid (levels of imidacloprid that they would encounter in the wild).

Specifically, researchers determined that consuming this pesticide harmed bee behavior and the colony’s ability to regulate their nest temperature. Tracking data gathered by the robot revealed that eating imidacloprid impaired normal bee behavior after both a single exposure and repeated exposure to the pesticide.

Example using the BEEtag software (https://github.com/jamescrall/BEEtag) to track individual bumblebees 24 hours after consuming 0.1 ng (blue) or 1.0 ng (red) of imidacloprid, or a control sucrose solution (green).

Bees that consumed daily doses of imidacloprid and bees that ate one single dose of imidacloprid both decreased the amount of time they spent active, the time they spent nursing, and the proportion of time they interacted with other bees compared to bees eating normal nectar. Bees eating imidacloprid also spend more time on the outside of the colony away from the food storage hub and nursery.

Crall et al. 2018, Figure 1 D-G. Colony mean percentage of time active over 7 consecutive days (with time indicating hours after exposure) during the daily imidacloprid exposure experiment . Filled circles represent mean activity levels for a single colony (averaged across all individual workers) for a single 5-min trial, and solid lines show mean values for treatment groups (control colonies, n = 9, in green; imidacloprid-exposed colonies, n = 9, in red). Gray blocks and Sun/Moon symbols show the 14:10 hour L:D cycle in the tracking arena. (E) Percentage of time engaged in nursing. (F) Mean distance to the nest center and (G) social network density [proportion of possible pairwise interactions between workers that actually occur, during a single 5-min trial

Crall et al. 2018, Figure 1 D-G. Colony mean percentage of time active over 7 consecutive days (with time indicating hours after exposure) during the daily imidacloprid exposure experiment . Filled circles represent mean activity levels for a single colony (averaged across all individual workers) for a single 5-min trial, and solid lines show mean values for treatment groups (control colonies, n = 9, in green; imidacloprid-exposed colonies, n = 9, in red). Gray blocks and Sun/Moon symbols show the 14:10 hour L:D cycle in the tracking arena. (E) Percentage of time engaged in nursing. (F) Mean distance to the nest center and (G) social network density [proportion of possible pairwise interactions between workers that actually occur, during a single 5-min trial

An experiment set in the field with natural conditions revealed that bee physiology is also harmed by short term pesticide consumption. Bee colonies weren’t able to regulate their nest’s temperature after 1-2 hours of intermittent feeding on nectar containing imidacloprid. Whereas, colonies feeding on normal nectar maintained nest temperatures above outdoor temperatures.

Crall et al. 2018, Figure 3 C. Brood versus outdoor temperatures for control, normal nectar fed colonies (C, green) and treated, imidacloprid fed (IM, red). Transparent markers show individual measurements across all colonies, and solid lines show LOESS-smoothed trends by treatment.

Crall et al. 2018, Figure 3 C. Brood versus outdoor temperatures for control, normal nectar fed colonies (C, green) and treated, imidacloprid fed (IM, red). Transparent markers show individual measurements across all colonies, and solid lines show LOESS-smoothed trends by treatment.

These elegant series of experiments present new automated technology that enables scientists to answer detailed questions about context specific insect behavior, movement, and social dynamics. The future possibilities are endless: How will bees respond to other pesticides, contaminates, or disease? How do these challenges affect other insect species? How do different insect species socially interact?

But also as a take-home message: don’t use or support neonicotinoid pesticides.
EPA’s action to protect pollinators & ways you can help

Erik Stokstad AAS Science provides an overview of the study, https://www.sciencemag.org/news/2018/11/new-tracking-system-could-show-last-how-pesticides-are-harming-bee-colonies

K.DeMoranville.jpg

About the author:
Kristen J. DeMoranville @Kris10DeMo is a Ph.D. student researching the effects of diet and long-distance flight on a migratory songbird in Scott McWilliams lab at the University of Rhode Island

Source: https://docs.wixstatic.com/ugd/f7293c_5c22905f830440dc8f24131ae5661c0b.pdf