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 about one-third 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, there are between 10 to 12 thousand beekeepers who manage 350 to 400 thousand 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.

Poisoning

Pesticide poisoning of honeybees depends on the bees’ developmental stage.

Larval 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. Decline in hive population due to loss of house bees who tend brood and larvae.
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.

Colony disruption and population decline in the hive can occur from the poisoning of bees in any developmental stage.

Bee Kills

There is only one symptom that is 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:

Irritable (aggressive), paralyzed, “chilled,” or other abnormally behaving bees.
Superseded queens, “banished” queens outside of the colony.

These symptoms are not definite signs of poisoning and other management problems can produce the same effects.

Protecting Bees

Understanding how bees forage helps to realize how susceptible to pesticides they are. Bees range two to five 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 around 8 AM to 5 PM when temperatures are above 55-60ºF. 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. Every apiary or bee yard must display the owner’s name, address, and telephone by Florida law.

Confining Bees

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.

Special Problems

Malathion and carbaryl (Sevin®) are two products that are especially harmful to honeybees. Both have been responsible for bee kills when the products have been used improperly—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 for 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.

Awareness on the part of growers about the interactions of honeybees and pesticides, and consideration of honeybee safety, keeps pesticide applications from affecting area bee colonies. Generally it is only when decisions are made without knowledge of, or regard for, honeybee safety that colonies are harmed.

For more information on the safe application and appropriate use of pesticides, contact your local Extension agent.