Pesticide Registration Toolkit

Hazard assessment for honeybees

Relevant documents
icon Hazard Assessment Table – Honeybees

Principle

A hazard assessment is based on the intrinsic toxicity of the product and does not take into account the degree of exposure of the bees to the pesticide. Note that exposure to a product with a relatively high hazard does not necessarily result a high risk, if the level of exposure is low. Alternatively, high exposure to a pesticide with a low hazard may well result in adverse effects on the bees.
By drawing conclusions about the risk of pesticide based only on a hazard assessment, one implicitly assumes that any exposure to the pesticide, irrespective of magnitude, will lead to the toxic effect identified in the hazard assessment. This may be valid for certain pesticides under certain circumstances, but is not generally the case. In many instances, the degree of exposure does determine risk (i.e. “the dose makes the poison”).
A hazard assessment is often done as a first step in a more elaborate risk assessment.

Data required

The following data can be used for a hazard assessment for honeybees

  • Attractiveness of the crop to bees
  • Acute oral LD50 for the honeybee
  • Acute contact LD50 for the honeybee
  • Residual toxicity on foliage (RT25 - time to 25% mortality)
  • Bee larvae (or bee brood) toxicity (LD50 and/or NOAEC) (for pesticides that may affect the larvae; e.g. insect growth regulators)
  • Chronic (10-day) oral toxicity (NOAEC) for the honeybee (if available)

More information on data requirements and testing guidelines for bees can be found in the Data Requirements module in this Toolkit.

Procedure

  1. Assess whether the crop(s) under review is attractive to (honey)bees.
    If the crop(s) on which the pesticide will be used is not attractive to bees, exposure of the insects is not likely. Crops that are attractive to bees are obviously those which are pollinated by bees, but also include crops for which bee pollination is not important but are visited for pollen, nectar or guttation fluids.
    Various lists of crops that are pollinated by bees or that are attractive to bees are available.
    Note that crops may be unattractive to bees, but certain weeds in the crop can be. In such a case, the use of the pesticide may still expose bees and a hazard or risk assessment is warranted.
     
  2. Evaluate possible route(s) and likelihood of exposure
    The routes and likelihood of exposure directly depend on the mode of action of the pesticide and the circumstances of its use, e.g. treated crop, crop management (weeding), timing of application(s) relative to flowering.
    Exposure is generally possible if the pesticide is applied when, or just before, bees are actively foraging on the plants. In addition, bees may be exposed to a systemic pesticide if it has been applied earlier in the growing season to the visited crop. 
    In some cases, exposure of bees is not likely. Examples are: use during winter when bees are not flying; pre-emergence use of herbicides, indoor use and use in glasshouses where bees are not used for pollination; seed treatments and granules except when there is systemic activity; products for dipping bulbs, etc. 
    However, any crops in which there are flowering weeds may present a risk of exposure, even if the crops themselves are not attractive to bees. In such cases, it is prudent to regard exposure as possible.
     
  3. Obtain relevant toxicity data
    Relevant toxicity data are those which are related to the likely routes of exposure.
    Honeybee toxicity can be obtained from the pesticide registration dossier (see data requirements, above).
    Toxicity data supplied by the applicant may be compared with verified (inter)national data available in reputable Pesticide properties databases.
     
  4. Classify acute and residual hazard
    There is no international classification of pesticide toxicity to bees.
    The US-EPA classifies pesticides according to their acute oral and contact toxicity. Depending on the outcome of these toxicity tests, pesticides are classified as follows:
     
    Hazard classification Acute LD50
    practically non‐toxic > 11 μg a.i./bee
    moderately toxic 2 – 11 μg a.i./bee
    highly toxic to bees   < 2 μg a.i./bee
      
    Foliar residue studies can be conducted to determine how long field‐weathered residues on vegetation remain toxic to honeybees (in the US this is generally done if the acute contact LD50 < 11 μg a.i./bee).
    Pesticides with an RT25 > 8 hours may be considered having an “extended residual toxicity”.
     
  5. Review other hazards
    Certain insecticides may not have a high acute toxicity to adults bees, but can be brought into the hive and affect bee brood. The results of single and multiple exposure bee brood tests may provide indications about the adverse effects of pesticides to bee larvae. If any effects are detected in a laboratory feeding test, cage and/or field testing is generally necessary.
    Chronic (often 10-day) toxicity data are increasingly being generated for honeybees. These tests may provide information about the toxic effects of longer term exposure of the adult bees to lower concentration of the pesticide.

Outcome of the hazard assessment

The outcome of the hazard assessment focusses on two:

  1. List of endpoints of the toxicity studies
  2. Hazard classification and/or description of hazards of the pesticide to honeybees (adults and larvae)
  3. List of circumstances in which the hazard may be expressed and likelihood of exposure of the bees
  4. List of potential honeybee hazard concerns

Hazard Assessment Table – Honeybees icon can be used to summarize the data.

Interpretation of the outcome

When interpreting the data, one should be mindful of the fact that the hazard of a pesticide product does not necessarily represent its risk, because exposure has not been taken into account.
Therefore, in principle, a risk assessment should be conducted (at least) of all pesticides that pose hazards of concern to honeybees. The risk assessment will show the level of risk of the pesticide under the proposed use conditions. Risk assessment methods are presented under the Assessment Methods Tool.

If a honeybee risk assessment cannot be conducted, the registration authority may decide about the acceptability of the pesticide on the basis of a hazard assessment alone. This is not recommended, but may be a necessity due to limited resources at the registration authority or the absence of appropriate risk assessment data or models.

If a high hazard to honeybees has been identified, the registration authority may decide to apply risk mitigation measures, such as hazard statements on the pesticide label (e.g. “do not apply to flowering crops), restricting the pesticide to specific crops or uses only, or not registering it. Further information on such measures can be found in the Risk Mitigation module.