Red Light, Green Light: Bee ‘Traffic Light’ is a Best Management Practices Tool

by | Jun 22, 2017

Protecting pollinators is a priority for the N.C. Department of Agriculture and Consumer Services

Farmers, growers, applicators, homeowners and beekeepers have a new tool to help reduce the pesticides risks to bees.  The Pesticide Toxicity to Bees “Traffic Light” uses a color-coded system to show pesticide toxicity levels. The traffic light, developed by the Structural Pest Control and Pesticides Division, is one of the latest tools provided on the N.C. Department of Agriculture’s Pollinator website.

Information on pesticides was gathered using information from the N.C. Agricultural Chemicals Manual and other resources. Pesticides are listed by their active ingredient and trade name. To search for toxicity levels, users can enter a pesticide name or active ingredient in the find function under the edit tab on their computer to search for a product. Products highlighted in green indicate they are relatively non toxic to bees. Products highlighted in yellow indicate moderate toxicity to bees. Red highlights means the active ingredient in the pesticide is highly toxic to bees.

The EPA uses two tests to evaluate toxicity to bees. The first test determines how much of the active ingredient it takes to kill bees. If it only takes a small amount to kill 50 percent (LD50) of the bees (≤ 2 µg/bee), then it is categorized as highly toxic. If it takes a little more to kill half of the bees (2-11 µg/bee), then it is considered moderately toxic. If it takes more than 11 µg/bee to kill half of the bees, then it is categorized as non-toxic to bees by acute contact. An “ug” is not the audible expression of frustration often heard when dealing with toxicology terms. The unit µg stands for micrograms. It is an extremely small unit of measure. Ten million micrograms would be the equivalent of .35 ounces.

The second test determines residual toxicity, or how long the pesticide remains toxic on foliage. In this test, researchers determine how long the pesticide remains toxic enough to kill 25 percent (RT25) of the bees on contact. A pesticide with an RT25 of eight hours or more is considered to have extended residual toxicity. For these pesticides, then it is best, and may be required by the label, to avoid application to areas in which bees may be foraging during the time interval indicated by the RT25. If the pesticide does not have extended residual toxicity, then it can be applied in the late evening after bees are done foraging and it will not be toxic to the bees the following day; the Bee Traffic Light denotes these pesticides by the sunset symbol.

Bees are critical for pollinating crops and the Bee Traffic Light is meant to be a tool to help pesticide applicators make informed decisions. Pesticide users are required by law to follow all label instructions to ensure the protection of health and the environment.  Check online for other tools to help develop a pollinator protection strategy for your farm or home.