Bees and Pesticides
The honeybee is only one of many bees and pollinators in Florida; however, it is the most important bee for Florida and the nation’s agricultural economy. Honeybees supply approximately 1/3 of the national food supply through their pollination activity.
Sometimes agricultural producers “rent” bee colonies for pollination, but most bee and pollination activity occurs naturally from bees in the area. In Florida, between 10,000 and 12,000 beekeepers manage 350,000 to 400,000 honeybee colonies.
Each year the beekeeping industry is impacted by pesticide use. Foraging bees come into contact with agricultural insecticides and pesticides. Cooperation between agricultural operators and beekeepers can minimize these effects.
Pesticide poisoning of honeybees depends on the bees’ developmental stage. Colony disruption and population decline in the hive can occur from the poisoning of bees in any developmental stage.
- Most susceptible to poisoning
- Killed by contaminated pollen and nectar
Adult house bee
- Active in the hive
- Tend larvae (brood)
- Killed by contaminated stored pollen
The loss of house bees, which tend brood and larvae, contributes to further declines in hive population.
Adult field bee
- Active outside the hive
- Forage for pollen and nectar to bring to the hive
- Killed by direct contact with pesticides and sprays
- Bring back contaminated pollen and nectar to the hive
Only one main symptom presents good evidence of pesticide poisoning—many dead and dying bees near a colony’s entrance. The dead bees are quickly removed by wind and scavengers, so beekeepers who do not frequently visit their hives may not know their bees have been poisoned.
Other signs of possible poisoning are as follows:
- Irritable (aggressive), paralyzed, “chilled,” or other abnormally behaving bees
- Superseded queens or “banished” queens outside of the colony
These symptoms are not definite signs of poisoning, and other management problems can produce the same effects.
Understanding how bees forage helps to realize how susceptible to pesticides they are. Bees range 2–5 miles from a colony and seek out nectar and pollen in a systematic way. Once a food source is found, bees tend to collect only from that single source until it is used up before switching plants.
Most major bee poisoning occurs when plants are in bloom. Bees that establish flight patterns in an area before a pesticide is applied usually are most affected. Bees that come to an area after pesticide applications are less affected since it takes time to scout and find food sources.
To eliminate damage to honeybees, pesticide applicators should keep the following suggestions in mind:
- Use only when needed. Factor in the value of beneficial insects (pollinators and predators) for crop yields when deciding whether or not to spray for pests.
- Do not spray while crops are in bloom. Apply during bud stage or after petal drop.
- Identify other blooms. Look for weeds or other plants that might be blooming and attractive to bees, even if the crop being sprayed is not in bloom.
- Apply when bees are not active. Bees fly from roughly 8 AM to 5 PM when temperatures are above 55ºF–60ºF. Early evening is the best time for pesticide application.
- Do not contaminate water. Bees use water to cool the hive and feed brood.
- Use less toxic compounds. Products hazardous to honeybees must say so on the label. Consult your local Extension agent for less-toxic compounds and use.
- Use less toxic formulations. Microcapsules, dusts, wettable powders, and ULVs are more hazardous than liquids and emulsifiable concentrates.
- Notify beekeepers. Beekeepers can move or confine bees if they have prior notification. Under Florida law, every apiary or bee yard must display the owner’s name, address, and telephone number.
Beekeepers can cover hives with burlap or coarse cloth. This keeps bees from foraging but lets them congregate outside of the hive. Sprinkling the covers every hour with water prevents overheating.
Never screen or seal colonies or cover with plastic sheeting. This can cause overheating, suffocation, and bee death.
Two products especially harmful to honeybees are malathion and carbaryl (Sevin®). Both have been responsible for bee kills when the products have been used improperly, such as under the wrong conditions, without beekeeper notification, and with the most toxic formulations.
Encapsulated methyl parathion (PennCap M®) and other microencapsulated pesticides are the most damaging to honeybees. We strongly recommend using this formulation only when honeybee exposure is not a possibility.
Cooperation and Communication
Protecting honeybees from pesticides requires cooperation not only between growers and beekeepers, but also with Extension agents and government officials.
Growers need to be aware about the interactions of honeybees and pesticides, consider honeybee safety, and keep pesticide applications from affecting area bee colonies. Generally colonies are only harmed when decisions are made without knowledge of or regard for honeybee safety.
For more information on the safe application and appropriate use of pesticides, contact your local Extension agent.
Adapted and excerpted from:
M. Sanford, Protecting Honey Bees from Pesticides (CIR534), Entomology and Nematology Department (rev. 09/2011).