Pesticides and Honey Bee Mortality


Revised October 1980
Pages 129 – 140


In a world where people expect and demand more food and fiber each year, all branches of agriculture must continuously adapt and improve to meet this challenge. Farmers now find it essential to annually increase efficiency and production to remain in business and to show a profit.

Many major agricultural changes took place in the 1950′s, shortly after World War II, when tractors replaced horses, chemical fertilizers replaced organic manure, aerial application of pesticides became commonplace, and farmers became increasingly conscious of business costs. At the same time, many farmers were encouraged to devote large acreages to the cultivation of a single crop, which necessitated the utilization of large quantities of synthetic fertilizers and pesticides to nourish and protect that crop. Consumers also came to expect all market fruits and vegetables to be completely free from insects and insect damage.

Thus, many growers found it advantageous to apply more and more pesticides each year. Unfortunately, some aspects of this agricultural modernization were not beneficial for beekeepers, whose needs were either frequently forgotten or ignored. Consequently, many honey bees were killed. To compensate, many commercial beekeepers had to keep larger numbers of honey bee colonies in a variety of locations to make up for losses from pesticides and to meet rising operating expenses. This interaction between the needs of crop farmers and the needs of beekeepers, coupled with frequent widespread application of the “newer” insecticides, such as parathion, proved devastating to thousands of colonies.

Not only do insecticides create problems for beekeepers, but herbicides have adverse effects as well. For example, farmers employ herbicides in the practice of clean cultivation, which destroys nearly all weeds along fencelines, irrigation ditches, and on wasteland. Under these circumstances, fewer nectar- or pollen-producing plants are left in farming regions, except for those plants under cultivation and consequently under insecticide treatment. The shift by farmers in some areas from planting vast acreages of alfalfa and clover to corn had a dramatic effect on the bee industry. Corn affords the bees no nectar, but many bees are killed while collecting pollen from insecticide-treated corn.

Another problem that has created difficulties for both crop farmers and beekeepers is the social and economic pressure to produce more food on fewer acres, since much fertile land has been taken over by shopping centers, housing projects, highways, and other projects designed to accommodate masses of people. Consequently, many beekeepers have been forced into areas of intensified agriculture where pesticide exposure is greatest. If pesticide application becomes too intense, the beekeeper again is excluded from large acreages; thus honey yields decrease.

On the brighter side, many farmers growing such crops as almonds, apples, cranberries, seed alfalfa, citrus fruits, and other cash crops have learned that pollination by honey bees and other insects is absolutely essential for maximum crop production. This dependency has resulted in a better understanding between crop producers and beekeepers. Unfortunately, however, the bee-mortality problem has been solved only partially. In other areas, very large numbers of honey bees still are killed each year by insecticides and other agricultural chemicals.

To illustrate the magnitude of the pesticide problem for bees, the quantity of pesticides produced and sold in the United States has increased every year since 1957, except for 1969 and 1970, when there were slight decreases. Production of synthetic organic pesticides in the United States in 1974 amounted to more than 1.4 billion pounds (709,000 tons). Of the total production, 650 million pounds were insecticides. Even after taking imports and exports into account, slightly more than half the production, 400,000 tons, of pesticide was applied in the United States (Fowler and Mahan 1976). Currently, there are more than 50 insecticides in common use with moderate to high toxicity to honey bees (Atkins 1977).

The exposure of honey bees to pesticides is an ever-changing problem for beekeepers, because each year new pesticides, as well as new formulations of the established ones, appear in the marketplace. The release of just one new chemical or different formulation has, at times, been devastating to honey bees. When Sevin (carbaryl) first was applied in orchards in the Northwestern United States, one beekeeper alone claimed to have lost several thousand colonies in less than a month. The heavy loss of colonies happened unexpectedly and so fast that a huge number of colonies were killed before remedial steps, such as moving the colonies, could be taken.

More recently in the same region, the change from the customary spray-form of methyl parathion to the new encapsulated form was blamed for the loss of several thousand colonies. Beekeepers were well aware of the highly toxic nature of methyl parathion, but they were not aware, or prepared, for the increased toxicity due to the greatly extended period over which the encapsulated chemical will kill bees.

Unfortunately, much of the information that beekeepers acquire on pesticides and honey bee mortality comes through personal observations when colonies are weakened or killed by new chemicals.

A tragic example of honey bee mortality was reported in Arizona, where the number of colonies dropped from 110,000 in 1964 to 53,000 in 1971-primarily because of the intensive, widespread cotton-spray program. Cotton has blossoms that are an attractive source of nectar over most of the summer. To protect the cotton, the farmer makes as many as a dozen applications of toxic insecticides to the plants during the summer. With few exceptions, bees cannot survive in this type of an environment (Moffet and others 1977). Another well-documented series of heavy bee losses due to pesticide poisoning comes from California, where beekeepers lost an average of 62,500 colonies a year from 1962 to 1973 (Atkins 1975).

Since the manufacture of pesticides develops millions of dollars annually for agricultural businesses through domestic and foreign sales, and because crop farmers see no easy alternatives to pesticide application at the present time, what hope is there for the beekeepers’ bees? Fortunately, there are methods of application, types of formulation, apicultural management practices, legislative measures, and other protective devices which can and do aid the honey bee and the beekeeper not only to survive but to pollinate crops and produce honey successfully in an environment often containing many poisonous chemicals.

The following information is presented to help the beekeeper better understand pesticides and to successfully meet the challenge of pesticides killing honey bees.

Classes of Pesticides 3

The need of human beings to effectively control their environment is most evident in their agricultural pursuits. Modern farming covers large tracts of land under uniform planting, and this has made pest control mandatory. The evolution of pest control agents originated with natural products such as arsenicals, petroleum oils, and toxins derived from plants (nicotine and rotenone, for example). The advent of DDT, which was synthesized in a laboratory, heralded an era in which a mature chemical industry would screen synthetic chemicals for pesticidal activity. This effort spawned an impressive array of insect control agents. The selection of control chemicals is large. However, these materials can be grouped conveniently according to general chemical properties and modes of action.

3 Toxicity of Pesticides to Honey Bees (Atkins et al. 1975) lists many commonly used pesticides according to relative toxicity.

Chlorinated Hydrocarbons

These include such important insecticides as DDT, BHC, toxaphene, and chlordane. The chemicals in this group are slowly reactive chemically, thus persistent in the environment. Biological degradation tends to be slow; hence, storage in fatty and muscle tissue causes these materials to become concentrated and enter our food chain.

The mode of action of chlorinated hydrocarbons is still a subject of active research. They are classified as neuroactive agents which block the transmission of nerve impulses. Specifically, for example, DDT prevents the normal sodium-potassium exchange in the sheath of the nerve fiber-this exchange being the means by which a message is transmitted along the nerve. Because chemicals such as DDT are not very chemically reactive, it is felt that the mechanism of reaction with the sheath is not chemical, but rather that the size and shape of a DDT molecule may fortuitously permit it to fit into the proteins of the sheath. Such conceptualizations of the toxicological processes have promoted the search for new chemicals with better toxicological and environmental properties.

Organophosphorus Insecticides

These, today, account for about 30 percent of the registered synthetic insecticides/acaricides in the United States. They possess the common characteristic of inhibiting the enzyme cholinesterase, which mediates the transmission of nerve signals. Hence, organophosphates also are neuro-active agents. As their name implies, these materials contain phosphorus, and as a group they include parathion, Systox, DDVP, and malathion. They are quite reactive chemically and are not regarded as persistent in our environment, unless they are microencapsulated.

Carbamate Insecticides

These also are inhibitors of cholinesterase and feature a nitrogen-containing unit known to chemists as a carbamate function. Members of this class of insecticide include carbaryl (Sevin), baygon, Furadan, landrin, and zectran. For the most part, these materials are easily biodegraded and do not constitute the residual hazard of the chlorinated hydrocarbon class of insecticides. Interestingly, cholinesterase inhibition tends to be reversible for mammals and insects alike. A sublethal dose can bring on the usual symptoms of nerve poisoning (tremors, loss of muscular control, incontinence, vomiting), but the poisoned animal will return to normalcy in a very short time.

Other Pesticides

A wide variety of other synthetic chemicals may be applied to crops on which bees may be foraging. Herbicides and fungicides have bases for their activity which render them relatively much less toxic to honey bees. Still such materials are present in the biosphere of the honey bee, and little information is currently available dealing with the effects of these chemicals in combination with insecticides-a situation which occurs often under normal field conditions. Moreover, such materials as herbicides and nonconventional insecticides (such as insect sex attractants and insect growth regulators) to which bees are being increasingly exposed likely will be transferred to honey and stored pollen with, as yet, incompletely documented results.

The toxicity of a specific pesticide is a composite of its physical and chemical properties, the method of formulation (description follows), and the inherent ability of the honey bee to deal with the material internally. If the pesticide is of high volatility (an example is the fumigant TEPP), then the chemical may be absorbed through the bee’s spiracles or respiratory system. Fortunately, TEPP is very quickly hydrolyzed-it reacts with moisture readily and is very nonpersistent. Absorption through the bee’s integument is the basis for contact toxicity. The physical properties of an insecticide and especially of its formulation would be largely responsible for the relative hazard from this mode of entry into the bee. Ingestion of contaminated pollen and nectar offers yet another route of entry. The alimentary tract may become altered or paralyzed, making feeding impossible, or the bee’s gut may cease to function. The ability of an insecticide to contaminate nectar and pollen would again be a composite of the physical/ chemical properties of the material, its formulation, and the time of application of the spray relative to bloom.

Due to the extensive measurements of E. L. Atkins, C. Johansen, and others, a large amount of toxicity data has been collected, which allows an assignment of the inherent relative toxicity of the many pesticides now in use. These data are the results of both lab and field tests in which the materials usually were examined in their most common formulations. The organophosphates and carbamates are the most toxic to honey bees, with Furadan (LD50 0.160µg/bee) and parathion (LD50 0.175µg/bee) high on the list.

A number of chemicals were classed as only moderately toxic (LD50 2-11µg/bee). Endrin, DDT, mirex, chlordane, Systox, and Phosvel are included in this group. It is of interest to note that several of these are chlorinated hydrocarbons. The lower toxicity of several of these chlorinated hydrocarbons may be due to an enhanced ability of the bee to degrade the compounds to nontoxic materials within its body. Resistance, or relative resistance, among insects often is an increased ability of the insect’s biochemical constitution to chemically dispose of the insecticide.

Among the relatively nontoxic pesticides are allethrin, Kepone, Kelthane, and most of the fungicides and herbicides. Extensive studies have not been conducted with such control chemicals as pheromones and growth regulators. However, a great deal of toxicity data regarding their effects on mammals, birds, and insects other than bees has been collected which indicate nontoxicity. The growth regulators, on the other hand, may well affect the nature and volume of the brood. More studies involving these chemicals seem desirable.

Nonchemical Control

Along with the beneficial aspects of chemical pesticides come problems such as contamination of the environment and killing of beneficial insects, many of which are honey bees. To reduce agriculture’s dependency on pesticides, a new concept of pest control has been developed called integrated pest management (IPM). Under IPM, all techniques and methods that are useful in controlling pests are used, including pesticides. However, a farmer applies a chemical pesticide only as a last resort. Primary reliance is on nonchemical controls, such as insect attractants, repellents, traps, insect-resistant plants, insect pathogens (disease), insect predators and parasites, time of planting, cultivation, time of harvest, sterilized insects, quarantines, and other practices. Not all of these techniques are utilized at the same time in controlling a pest; however, all of the control methods are considered noninjurious to honey bees, except for chemical control. Where possible, beekeepers should encourage farmers to use IPM techniques.

Application Methods

Once a compound is shown to be toxic to insects in laboratory tests, we must learn how to apply it efficiently to pests under field conditions. Considerable variations in toxicity toward a particular insect are sometimes seen when the insecticide is applied in different carriers. Therefore, the preparation of suitable formulations for an insecticide is a vital part of its development for practical use and generally will determine the particular pest control situation in which it may he employed-as well as the degree of the danger to foraging pollinators such as honey bees.

At one time, there were more than 1,200 formulations in the United States based on DDT alone, and another 1,500 based on other chlorinated hydrocarbons.

Dusts can be made by mixing insecticides, which are solids (DDT, carbaryl), with an inert solid for a vehicle which sticks to the foliage. Because the exterior of bees is largely waxy and hairy, the dust adheres quite tenaciously to the bees as well. The insecticide may be dissolved in an organic solvent (xylene, kerosene) and the resulting solution sprayed. The solvent provides penetrating power, and the rate of evaporation of the insecticide from aerosolized portions of the spray may offer greater respiratory hazard to bees. An aqueous (water) suspension of the insecticide may be made if it is formulated as a wettable powder. Once the spray contacts the foliage, the water evaporates and exposes the insecticide to the environment in much the same way as a dust. Another formulation bears the name emulsifiable concentrate (EC). A solution of the insecticide in oil containing a detergent substance will form an emulsion (a suspension of finely divided liquid particles). Again, when the water dries from such a spray, the insecticide becomes exposed on the surface of the foliage. Such a spray has less penetrating power and is more evenly disseminated than the wettable powder formulation.

Microencapsulated Insecticides

Of considerable concern is the encapsulated insecticide formulation, such as Penncap-M, containing methyl parathion. The insecticide is dissolved in an organic chemical, then treated with another chemical with which it reacts to form a polymer. The insecticide molecules become imbedded in the polymer matrix, and the resulting free-flowing powder (having a particle size of 10 to 50µ) is sprayed as a water emulsion. After the water has dried, the particles behave much like a dust spray, with the exception that contact toxicity is rather minimal because the insecticide is within the particle (capsule). Toxic action is due primarily to release of the insecticide through the capsule walls as a vapor (gas). Beekeepers should be warned that bees will, in fact, carry the capsules to the hive along with pollen. Moreover, in field tests, foliage sprayed with Penncap-M remained toxic for a much longer period of time than did foliage sprayed with methyl parathion formulated as an emulsifiable oil.

While debate continues on the subject of the relative merits of different formulations for insect control and bee welfare, it is accurate to say that there is no safe formulation where honey bees are concerned, and each formulation has its unique hazards. A list of insecticide formulations in order of decreasing hazard to bees follows: Dust; wettable powder; flowable , emulsifiable concentrate or soluble powder or liquid solution; and granular formulation. The position of encapsulated insecticides has not yet been well defined, but may be more toxic to bees than are dust formulations. Because of the rather insidious nature of encapsulated formulations such as Penncap-M, however, beekeepers should be particularly cautious about exposing their foraging bees to such materials.

Pesticide Drift

Small particles of pesticides often become suspended in the atmosphere as a result of wind currents or heated air rising. This contamination of the air frequently kills honey bees, especially when the poison settles on plants where the blossoms are attracting bees. Frequently, the farmer applies the pesticide to a crop not attractive to bees, but the wind blows the poison onto a cultivated crop or to nearby weeds where bees are actively foraging for nectar or pollen, or both. The outcome can be catastrophic with many adult field bees dying (fig. 1). If the pesticide drifts or is blown into the entrance of a hive, many or all house bees and brood may succumb. Pesticide drift that is most damaging to bees usually originates in a field a short distance (1 or 2 miles or less) from the point of contact with the bee. Beekeepers, however, occasionally report drift over several miles (less than 10) that results in serious adult bee mortality. Long-range drift does occur, but noticeable damage to adult bee populations is doubtful because of the enormous dilution factor.

FIGURE 1.-A double swirl of pesticide containing dust may effectively contain insect pests, but it also can be devastating to honey bee and wild bee populations-if the target plants are in bloom or the pesticide drifts onto a nearby crop that is being visited by bees.

Signs of Bee Mortality

Outside the Colony

The most obvious indication of heavy exposure to poisons is the heavy accumulation of dead or dying bees at the hive entrance and on the ground between the colonies (fig. 2). (In strong colonies, natural mortality of up to 100 dead adult bees per day is a normal die-off rate. When the rate exceeds 100 per day, then poisoning may be suspected.) Individual bees that have been poisoned, frequently are seen crawling on the ground near the entrance or twirling on their side in a tight circle. Others appear to be weak or paralyzed. These gross symptoms of poisoning vary with the type of pesticide and the degree of exposure. Foraging bees also may die in the field or on the flight back to the hive.

FIGURE 2.-Large-scale kills: Some pesticides kill bees in the field, while others kill the bees in or near the hive.

In severe cases, beekeepers and scientists have reported dead bees dropping like rain after an aerial spray of a contact poison, such as methyl parathion, had been applied to a field of blossoms during the middle of the day. Frequently, the bees that die away from the hive are difficult to find since they drop into vegetation or dry up and the wind blows them away. The inability to find the dead bees often leads to the false conclusion that the colonies did not suffer a loss of population. The useful aspect of bees dying away from the hive is that poisoned nectar and/or pollen are not brought into the hive, where they might be fed to the immature bees (brood) or stored in the combs. This may inadvertently protect the honey harvested for human consumption from pesticide contamination.

Inside the Colony

Bees die from various causes, and sometimes the cause of death may be difficult to determine. However, in moderate to heavy losses resulting from pesticide exposure, the problem often can be detected as soon as the hive is opened-the population is gone! Usually this loss occurs during warm weather when crops or weeds are being treated. Most frequently, the field bees are first to encounter the poison, but in more severe poisoning the house bees also die. When the house bees die, the brood will show signs of neglect or poisoning and many, or all, immature bees still in the cells may die. If a strong colony (three or more deep hive bodies) loses its foraging bees, nectar and pollen collection will be drastically reduced, but the population could recover in a few weeks. If the foragers and hive bees are lost, however, the colony may never recover and frequently will perish during the winter. The economic ramifications of a population loss depend on the season when the loss occurs. For example, if the field force is lost just before the colony is to be rented for pollination, or package bees shook, or the main nectar flow-the economic value of the entire colony would be lost.

Atypical Losses

Most pesticides are applied when the weather is warm and sunny. When a colony suffers a heavy loss of bees during favorable weather, pesticides frequently are suspected and usually are the cause of death. (Exceptions do occur, such as treatment of apple and almond blossoms during less favorable weather.) When conditions are cold and rainy, large numbers of bees often die, but not from pesticide exposure. More often, starvation, nosema disease, or disappearing disease account for the losses. Adult populations also may dwindle because of a poor queen or swarming. Sometimes, pesticides are blamed for losses due to these other factors.

Protection of Bees

Although the applicator of pesticides frequently is responsible for the poisoning of honey bees, the beekeeper should be aware of management techniques that can be used to lessen the damage or even, in some situations, avoid the problem. Several management practices are known that may help protect bees from pesticide-caused mortality.


FIGURE 3.-Many environmental factors contribute to a successful honey crop, but freedom from pesticide damage is a major one. When plants are treated with a pesticide while in bloom, the nectar and pollen may become contaminated. However, pesticides have not been found to contaminate honey stored in hives because foraging bees carrying poisoned nectar die before depositing the honey in their hive.

Timing the application of a pesticide, and especially insecticides, can be extremely important. Treatments can and should be applied only when bees are not foraging for nectar or pollen. If bee-attractive plants need to be treated while in bloom, they should be treated at night or in the early morning or late evening when the bees are not flying. Recently, night treatments have been used successfully in southern California. Another new concept is to determine the time of day when each species of plant secretes nectar and treat the plants when they are not attracting bees (fig. 3).

Occasionally, the time of year is important-namely, treating when optimum control of a crop pest can be achieved and be least harmful to honey bees. As an example, alfalfa should be sprayed for weevil control in autumn rather than spring or not until after the first cutting in early summer. Finally, advise everyone to use pesticides only when absolutely necessary.


Relocation of colonies may be desirable if a regime of repeated applications of insecticide is followed near an apiary. Information on the type of pesticides used and the frequency of application should be considered before moving colonies to a new location. Sometimes moving colonies, even for short distances or for brief periods 24 to 48 hours to avoid short-residual poison sprays and dusts, may be the best solution to the bee-mortality problem. Moving colonies, however, can be costly, not only in terms of vehicle expenses and labor, but often queens are killed or injured during the move and the “morale” of the colony may be disrupted for several days. Nectar storage can be reduced, apparently because of the need for the bees to reorientate to the new bee pastures. Unfortunately, some areas are dangerous enough to bees for a beekeeper to avoid altogether, thus requiring a permanent move to an area with lower pesticide exposure. (New areas with low or no pesticide exposure and satisfactory honey production are difficult to find.) Pesticide-free sanctuaries for bees have been tried in the Northwestern United States, but they have proved impractical or unsuccessful.

Field Protection Techniques

Field protection of bees to alleviate damage by insecticides can be accomplished in several ways. One successful technique is to cover each colony with a large burlap sack shortly before the insecticide is applied. Covering the hive entrance with the burlap prevents foraging during the day. The cover is removed at the end of the day when it is too dark for the bees to forage. Where colonies are covered, water should be applied to the burlap every 1 to 3 hours to cool the exterior portions and as a water source for the bees cooling the interior of the hive. A new device, the Wardecker Waterer (Moffett et al. 1977), which provides a reservoir of water within the hive, proved successful in supplying water to covered colonies in the Southwestern United States during periods when air temperatures were 100°F or higher for several weeks. This waterer is basically a modified shallow super. Colonies equipped with this device need no water applied to the burlap cover during confinement.

Whenever possible, it is always best to locate beeyards outside the spray/dust pattern rather than within the treated field. Moreover, colonies weakened by insecticide treatment should be fed sugar syrup and pollen cake to stimulate brood production as an aid to population recovery. Frequently, weak colonies must be united to save the remaining bees and brood or a queenless package of bees added to the damaged colony to strengthen the population.

If a pesticide carried by the bees infiltrates the combs and contaminates the nectar or pollen, or both, then the combs may need to be replaced before a colony will recover. Contaminated combs either may be soaked in water to help in the removal of stored pollen or the entire comb melted and replaced with wax foundation. Before washing or melting combs, however, a sample of the pollen, wax, and honey should be analyzed chemically to determine the amount of pesticide residue present, if any.

Another form of protection is direct and effective communication between beekeepers and local farmers. When farmers are educated to understand the complexities of a bee business, they often are more sympathetic about the problems of beekeepers, such as insecticide damage. Beekeepers should make their presence known as well as the location of each beeyard. Register the location of each apiary with the State bee inspector or other designated officials. In addition, post a sign in each apiary with the name and address of the owner.

Resistance to Pesticides

Genetic stocks of honey bees that have a higher level of tolerance to certain pesticides have been developed. None of these stocks of bees, however, has been developed commercially-mainly because resistance to one chemical poison would not necessarily protect the bees from other pesticides, and any heavy exposure of “resistant” bees still would cause bee mortality. Incorporating many desirable genetic characteristics, such as gentleness, good honey production, nonswarming, successful wintering, and pesticide resistance, into a stock of honey bees is difficult and expensive.

Selective Toxicity of Pesticides

An important facet in protecting bees is to educate pesticide fieldmen and pesticide applicators concerning the problems beekeepers face from pesticides-and to encourage the applicators to treat a field at a time and in a way least injurious to honey bees. They should always use the least toxic chemical that will achieve the desired results. This education can be accomplished through personal contacts, magazine and newspaper articles, and possibly best of all by discussion sessions between applicators, beekeepers, pesticide fieldmen, and apiculture scientists organized by the county agricultural agent or someone in a similar position of agricultural leadership.


Chemical repellents have been studied for many years, especially by E. L. Atkins of the University of California. The repellent is added to the pesticide before field application and is intended to discourage bees from visiting plants until the pesticide becomes relatively nontoxic. Field tests showed several compounds to have repellency, but more research is needed before they are used commercially by farmers.

Bee Recovery

When colonies sustain the loss of part or even most of their foraging bees, most frequently the beekeeper need only wait a couple of weeks and “new” bees in the hive will emerge and take over the field duties.

In severe mortality where all the field bees and many house bees have been lost, the beekeeper will need to resort to one or more of the following management techniques: Feed pollen and/or pollen substitute, add a queenless package, feed sugar syrup, move to an area with at least some natural nectar and pollen available that is relatively free of all pesticides (these areas are difficult to find nowadays), or unite two weak colonies. Sometimes, the contaminated combs must be removed and replaced with unexposed combs or frames of foundation. Weakened colonies should be protected from factors causing stress-such as cold temperature, excess heat, and lack of water. Factors favoring increased brood rearing aid colonies in their recovery.

Programs to Aid Beekeepers

Honey Bee Indemnity Program

For many years, beekeepers lost large numbers of colonies following the application of insecticides that had been approved by the Federal Government. Since the beekeepers received no compensation for these losses, the Government enacted national legislation to partially repay each beekeeper for pesticide-killed bees. Beekeepers who exercised reasonable precautions to avoid pesticide damage but still lost bees could apply for indemnity payments after January 1, 1967. The main goal of this program was to aid the bee industry in remaining financially stable and to ensure that enough strong colonies would be available to pollinate agricultural crops nationwide. This goal has been accomplished.

The Agricultural Stabilization and Conservation Service (ASCS) administers the indemnity program. When beekeepers have a loss, they should contact the nearest county ASCS office immediately. An ASCS inspector will check the colonies and determine the extent of the damage. The inspector also will assist the beekeeper in filing a claim. The payment is based on the population size in a colony before and after exposure to the pesticide. The indemnity program, however, is not a substitute for good bee management designed to avoid areas of heavy application of pesticides.

To accurately establish that a loss occurred, beekeepers should maintain detailed records of their colonies, noting by date such items as colony condition, population size, syrup and pollen feeding, and honey production. The more detailed the records, the easier it is to establish the true magnitude of a loss and receive reasonable compensation.

Pesticide Detection and Analysis

Residues of pesticides may be present as the original pesticide or as an identifiable degradation product, or both. Frequently, the amount of residue involved is extremely small. Analysis of these residues consists primarily of:

(1) Blending and extracting the biological material (such as bees and pollen) with a suitable solvent system so as to maximize the recovery of those pesticides whose presence is suspected, and their metabolities. This eliminates the bulk of the biological substrate.

(2) A series of liquid-liquid extractions and column chromatographies planned so as to further separate the residues from other materials of biological origin.

(3) Detection of the residues at the highest possible sensitivity to avoid interferences from substances not previously removed. A very fast method for cleanup, which is increasing in use, is gel permeation chromatography. Large molecules of biological origin emerge from the column first, thereby trimming the crude extract down directly to a much cleaner sample.

The most popular detection device is gas-liquid chromatography, wherein the residue-containing sample is volatilized and chromatographed as a vapor (fig. 4). A variety of detectors may be employed at the exit of the chromatography column, including element-specific types which will “see” only chemicals containing nitrogen, phosphorus, or sulfur. Since the presence in biological specimens of interfering substances containing these elements is unlikely, procedures employing specific detectors generally require less initial “cleanup” and are growing in popularity. Thin-layer and paper-chromatography also are useful for establishing the identity of pesticide residues. The ultimate visualization for detection usually involves spraying the chromatography plates with a chemical that reacts with the pesticide/metabolite to produce a characteristic color. Unfortunately, the method is less useful for quantitation.

FIGURE 4.-A gas chromatograph is used by scientists to detect minute quantities of pesticide residue in bees and bee products and on plants.

Mass spectroscopy also is used for residue analysis. Currently, the method lacks the sensitivity required, and the cost of equipment prevents its more general use. However, fluorometric methods are gaining adherents because of improved sensitivity and the rather minimal sample preparation required. The residue must be capable of absorbing visible or ultraviolet light. The intensity of the reemitted light is measured at some suitable wave length. This intensity can be compared with standards and functions as a quantitative measure of the residue. Current research centers on altering nonfluorescing pesticides so as to render them fluorescent and hence detectable by this method, and on applying high-pressure liquid chromatography employing ultraviolet detecting equipment for rapid cleanup, detection, and quantitation.

Government Regulation

For many years, governments have legislated the amounts of poisonous chemicals permitted in foodstuffs for human consumption. In the United States and other countries, there are stringent regulations and requirements on pesticide manufacturers to produce toxicity and persistence data before they are allowed to market any pesticide. One difficulty of such legislation is the wide divergence of opinion among pharmacologists and toxicologists as to the hazard of any pesticide. This can be demonstrated by the variation in tolerances set on the organochlorine insecticides by different countries.

The Environmental Protection Agency (EPA) was created in 1970 in response to public concern over pollution of the environment by substances including pesticides. EPA is “to prevent and abate degradation of the environment and to promote environmental enhancement” (Federal Register 1971). This independent agency acquired the authority to monitor and license pesticides (formerly a USDA assignment). EPA thereby regulates the use of all pesticides in the United States through the registration of these materials. EPA also sets tolerance levels in food (formerly a Food and Drug Administration (FDA) assignment) and controls radiation standards (formerly an Atomic Energy Commission (AEC) assignment). FDA, however, retained the power to regulate the final limits of pesticide residues in foods. This is accomplished by spot-checking, sampling, and occasional confiscation. USDA has retained the power to regulate the pattern of use for agricultural pesticides through recommendations resulting from field testing by USDA and university scientists and from State extension specialists.

Pesticide Applicator Certification

In 1972, Congress passed an amended version of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and gave the EPA the responsibility for carrying out the provisions of the act. Under the act, many people who apply pesticides are required to pass an examination or otherwise demonstrate their knowledge on proper use of pesticides. The Federal Government requested that each State set up a program to certify people such as commercial applicators (aerial and ground equipment) and even certain farmers who apply restricted use pesticides. (These pesticides are many organophosphates and some carbamates, depending on dosage, formulation, and site of application.) Many States are conducting certification courses or workshops to update applicators’ knowledge of pesticides and to aid them in qualifying for certification. Certification under this act should benefit the beekeeping industry through more judicious use of pesticides.

Research on Pesticides

The chemical-manufacturing industry frequently markets new pesticides or new formulations of previously marketed compounds. These new products often create new or additional problems for beekeepers by killing bees. Consequently, research programs have been established in universities and at SEA bee-research laboratories to find practical ways of reducing or avoiding honey bee mortality. One recently discovered method for reducing mortality is the Wardecker waterer device, which provides bees with an internal source of clean and readily available water for heat regulation of hives and nutrition. Another method that is currently being researched is use of chemical repellents mixed with pesticides that deter bees from entering fields.

State Laws Protecting Bees

Some States have laws to help protect honey bees from pesticide exposure. Such laws encourage the use of the recommended amounts of pesticide, application of pesticide when plants are not highly attractive to bees, abstention from application when climatic temperatures are high and wind velocity above 5 to 10 mph, aerial application in the early morning or late evening only, and notification of beekeepers 1 day or more before pesticide application near their colonies. Beekeepers in some States are required to register the location of their beeyards, so that a notification program can be utilized.

Sources of Information on Honey Bee Exposure to Pesticides

Often one of the following individuals or groups can answer questions or render aid:

- County agricultural agent
- State bee inspector
- State entomologist
- State department of agriculture
- Department of entomology, State university
- Honey bee laboratories, USDA
- State and national beekeeping organizations
- Pesticide manufacturing companies
- County Agricultural Stabilization and Conservation Service of USDA

References 4

Annual Review of Entomology 13:213-238.

1975. INJURY TO HONEY BEES BY POISONING. In The hive and the honey bee. p. 663-696. Dadant & Sons, Hamilton, Ill.

_________L. D. ANDERSON, and E. A. GREYWOOD.
1970. RESEARCH ON THE EFFECT OF PESTICIDES ON HONEY BEES 1968-69. Parts I and II. American Bee Journal 110:387-389; 426-429.

1975. TOXICITY OF PESTICIDES TO HONEY BEES. University of California, Division of Agricultural Science, Leaflet 2286.

_________L. D. ANDERSON, D. KELLUM, and K. W. NEUMAN.
1976. PROTECTING HONEY BEES FROM PESTICIDES. University of California, Division of Agricultural Science, Leaflet 2883.



1977. PESTICIDES AND POLLINATORS. Annual Review of Entomology 22:177-192.

1972. INSECTICIDE FORMULATIONS AND THEIR TOXICITY TO HONEY BEES. Journal of Apicultural Research 11 :59-62.

1975. TOXICOLOGY OF INSECTICIDES. Chapters 3, p. 47-103; 4, p. 105-163. Plenum Press, New York.

1977. THE WARDECKER WATERER. American Bee Journal 117(6): 364-365; 378.


1975. PEST CONTROL: AN ASSESSMENT OF PRESENT AND ALTERNATIVE TECHNOLOGIES. 506 p. vol. 1, Report of the Executive Committee, National Academy of Sciences, Washington, D.C.

1952. INSECTICIDES AND BEES. In U.S. Department OF Agriculture, Yearbook of Agriculture (Insects) 1952:131-135.

4 These publications usually are available from college and public libraries.