Not all pesticides are equally hazardous to bees. Prevention of bee losses is a joint responsibility of the spray operator, grower, and beekeeper. It is fostered by mutual understanding and cooperation which includes the exchange of information before pesticides damaging to bees are used. Pesticides work in two ways to reduce bee populations. Many pesticides that are necessary in crop production are highly toxic to honey bees. Secondly, the use of herbicides reduces the acreages of attractive plants for the bees to forage on. Pesticide damage to colonies takes many forms. Bees may be poisoned when they feed on nectar or pollen contaminated with certain pesticides. They may also be poisoned when they fly through a cloud of pesticide dust or spray, or walk on the treated parts of a plant. They may be overcome by the fuming action of certain pesticides, either in the field or in the hive if the material has drifted there. Colonies may be completely destroyed, but most commonly, only field bees are killed. Loss of field bees can be serious because the factor contributing most to a beekeepers success in honey production or pollination is his ability to build up colonies that are strong in numbers of bees. If the field force is destroyed by pesticides, the whole colony will be weakened and may remain weak for some time; the queen may reduce egg-laying or be killed by the workers; the colony may fail to survive the winter or obtain a crop of honey or be useful for crop-pollination.

Beekeepers need to acquaint themselves with the pesticides that are commonly used in their area. When practicable, place colonies away from fields that are routinely treated with pesticides. Let farmers in your area know where your bees are located. Post your name, address, and phone numbers in a conspicuous place in your apiary. Be prepared to confine or remove your bees if you are notified that a hazardous pesticide is to be applied.

Colonies may be covered with plastic sheeting that will confine the bees and exclude pesticide spray, dust, or fumes. However, heat builds up rapidly under plastic exposed to the sun. Therefore, the confinement should be limited to a few hours after dawn. This may be long enough to protect the bees from some pesticides that do not have a long residual effect.

Hives may be covered with wet burlap for a day or more, even during the hottest weather, and the bees will not suffer from lack of air or water. They should be covered at night when all the bees are in the hives. During the day, soak the burlap with water at least once every hour. Covering colonies is usually not practical where repeated applications are made. Burlap probably would not give complete protection to colonies located in a field treated with a pesticide that has fumigating action.

Bees use water in their food and for cooling the hive. Colonies under confinement soon become stressed if they lack water. Water shortage causes symptoms similar to spray poisoning. If wet burlap is used to cover colonies, it provides water for the bees and helps cool the colony. If your colonies are in danger of repeated exposure to a pesticide, the safest way to protect them is by moving them to a new site. Since colonies often must be moved to a less satisfactory location where they may still be in danger of pesticide poisoning, moving is recommended only as an emergency measure. The following tables of information will allow you to determine which pesticides are highly toxic to bees so you can avoid placing colonies in areas that are routinely treated with them.

A. Pesticide spray formulations vary significantly in their toxicity to bees. Wettable powder formulations are often more hazardous to bees than either emulsifiable or water soluble concentrate formulations.

B. With few exceptions, pesticides applies as dusts are more hazardous to honey bees than those applied as sprays because of greater drift.

C. Fine sprays are less toxic than coarse sprays.

D. Sprays of undiluted technical pesticide (ULV or ultra-low volume applications) may be more toxic than diluted sprays.

E. Granular applications are usually the safest method of treatment.

F. Pesticide applications by aircraft usually are more hazardous to bees than applications by ground equipment, due to increased drift.

G. The hazard to bees apparently increases when insecticides are microencapsulated. The minute capsules can be carried back to the colony in the same manner that pollen is carried, and can kill brood and young adult bees.

H. At present there are no safe, effective repellents that will keep bees away from treated areas.

Beekeeping Topics | Extension Publications | Mid-Atlantic Apiculture