The Curious Beekeeper

 September 2014

No September Article

August 2014


Sampling for Pesticide Residues, Part 1:

Deciding What to Sample

Pesticide Research Institute


In the last Curious Beekeeper article, we talked about the different kinds of samples that could be taken—bees, pollen, wax, honey, plants, soil, water—and described the advantages and disadvantages of analyzing each. In this installment of The Curious Beekeeper, we provide logistical guidance on taking samples from your apiary without contaminating the samples through contact with other materials or another sample. We also outline best practices for documenting the process and provide insight on interpreting and using sample results.

Documenting the Process
Properly documenting the sampling process is essential to drawing meaningful conclusions from your results. Although it is not guaranteed that pesticide residue analysis will solve your honey bee mystery, improper or inadequate documentation will very likely diminish the utility of your results.

One of the most important things to do when you are sampling hive materials is to compile detailed information concerning your samples. Document the reasons for sampling, the collection date, sample location (as detailed as possible), and the type of samples taken (pollen, wax, brood, bees, honey, nectar, or plants). Also record any other relevant observations about the bees, the brood, the queen, hive strength, recent pesticide applications, the crops within flight distance, and/or anything that may be relevant for assessing what went wrong with the hive.

A sample name or number should be assigned to each individual sample. This step helps to ensure proper correlation of results from the laboratory to a specific sample. More detailed information for a given sample name should be recorded in your personal records (described above), but not shared with the lab. Make sure that the sample name is consistent between your records and the materials you send to the lab (see below).

The final documentation step is to fill out the Chain of Custody (COC) form provided by the laboratory doing the analysis. Most labs have one that can be downloaded from their web site. The COC provides a list of the samples contained in the shipping box by sample number and sample type (pollen, wax, bees, etc.), as well as the type of analysis requested. The COC form also is a legal document providing documentation of the movement and location of the samples from the time they were taken until the lab receives them, and includes the date the samples were taken from the apiary, shipped to the lab and received by the lab, the signature(s) of the people who have handled the samples, as well as information on how the samples were handled and stored (preferably kept cold at all times to prevent degradation).

If there is a legal challenge related to a bee-kill incident, the COC form provides essential documentation of sample handling. Samples taken by the beekeeper may not be accepted by enforcement agencies or by a court as valid even with a COC, but if there is no COC, the results will certainly not be accepted as valid.

Clean Sampling Technique is Critical

If you wish to obtain an accurate sampling of pesticides inside the hive, it is critical to ensure that the sample is not contaminated through the sampling process. Potential sources of pesticide contamination include the hive body, beekeeping gloves, the hive tool, and sampling tools. Beehives that are placed in orchards and near fields are subject to spray drift or direct sprays that contaminate the outside of the hive. Pesticide residues can be transferred from the hive body to gloves when the beekeeper touches the hive. The hive tool and sampling tools can transfer pesticide residues between samples.

The potential for contamination can be greatly reduced by protecting your work surface with a clean (unscented) plastic trash bag, wearing single-use latex or nitrile gloves over beekeeping gloves when taking the sample, and cleaning the hive tool and any sampling implements between samples with rubbing alcohol.

It is usually easier to keep a clean workspace indoors, so preliminary sample collection should be done in the apiary by taking a frame out of the hive (for pollen, wax, brood, and honey samples), shaking the bees off and placing the frame in a clean plastic trash bag to take home for further processing. Adult bee samples can be taken directly in the apiary by placing them in a Ziploc® bag, but avoid mixing twigs, grass or dirt into the sample. If you cannot process the samples right away, freeze them as soon as possible to preserve them.

Sample Preparation
Proper sample preparation begins with labeling and requires attention to detail. Careful labeling of the sample containers with indelible ink will ensure that different samples are readily identifiable and the results can easily be correlated to a particular apiary and hive. The sample name or number should be indicated on the sample container(s), the COC form, and any personal records for reference later in the sampling process (see above).

It is equally important to provide sufficient material for analysis. Most labs will be able to analyze samples as small as three grams (about a tablespoon of pollen, honey, or compressed wax, see Figure 1), but providing more ...