Case Study

Differential Weighing Gauges Bee Pesticide Response

A European Testing Lab Tracks Bee Sensitivity to Novel Plant Protection Products in Compliance with OECD Guidelines

An agricultural testing lab based in Europe conducts field and laboratory studies to determine the safety and efficacy of new agrochemicals and crop varieties. Renowned for its expertise in post-harvest trials, it has developed a GLP/GEP-accredited portfolio of test systems covering lab, semi-field and field studies, emphasizing ecotoxicology as well as efficacy and residue trials. 

Providing scientific resources to assess novel plant-protection products (PPPs) developed by its customers, its focus is PPPs’ effects on honeybee survival, development and behavior, to ensure the maintenance of healthy bee populations and their continued pollination of both wild and crop species.

The testing lab assays various PPP parameters following Organization for Economic Cooperation and Development (OECD) guidelines. These include acute oral and contact toxicity (OECD 213/214), as well as monitoring of feeding behavior during 10-day oral exposure (OECD 245). For all these procedures, bees are housed in the laboratory under temperature and humidity control; mortality and behavior are recorded at the same time each day.

Food consumption is a crucial metric for each assessment. Not only is it an indication of behavior, but it permits the calculation of safe PPP exposure levels.

Yet with ongoing tests of numerous substances undertaken in parallel, each with several replicates, at varying concentrations, and over more than one day, the lab’s scientists wished to optimize their collection and management of data, and approached METTLER TOLEDO for help. Excellence weighing equipment and LabX® laboratory software now support their activities, increasing the traceability, and efficiency of collection, of their ecotoxicology assay data.

Detailed data-recording
Scientists use differential weighing before and after bee feeding to determine food consumption, noting the number of living bees at the start of each feeding interval, as well as the mean daily consumption of feeding solution per treatment, per replicate. With the data, they can calculate the mean uptake of PPP per bee per day, as well as the cumulative uptake of the substance over the course of the assay.

Automated capture of results

To assist not only with measurements, but with the systematic documentation of each data point, METTLER TOLEDO specialists suggested the XSR Micro-Analytical Balance. With 0.01 mg readability, the balance easily afforded the high accuracy necessary for rigorous differential weighing results. Addition of the LabX software enabled the seamless capture of experimental data over time, and permitted the lab’s scientists to design a comprehensive SOP to ensure that measurements were standardized.

With the new system in place, operator influence has been reduced, and the tedium of manual data-entry all but eliminated. LabX automatically calculates results and generates reports, freeing the scientists for other tasks, and reinforcing their confidence that PPP safety is properly determined.

XSR Micro-Analytical Balance
XSR Micro-Analytical Balance
Bee Pesticide Response
Bee Pesticide Response

Standard methods to probe PPP safety and efficacy

To determine acute oral toxicity (OECD 213/214), bees are fed in the laboratory with a test PPP substance dissolved in a sucrose solution. Mortality is recorded for 48 to 96 hours and LD50 values are subsequently calculated.

During chronic oral exposure (OECD 245), young bees are exposed to 50% (w/v) aqueous sucrose solution containing the test PPP by continuous feeding, ad libitum, over 10 days. Mortality and behavioral abnormalities are observed and recorded daily at the same time. The effects of the PPP over time are then evaluated against a control group to determine the median lethal concentration (LC50), median lethal dietary dose (LDD50), no observed effect concentration (NOEC) and no observed effect dietary dose (NOEDD).