The poisoning of bees by pesticides is a major problem affecting the efficiency of bees not only in the production of honey but also in crop pollination (fig. 30). This problem is not limited to the United States but occurs in all other countries that have highly developed agriculture. The problem is complex with many ramifications, frequently interwoven with emotion. The greater part of the problem is associated with insecticides applied to cultivated crops--cotton, fruits, vegetables, grains, and legumes. Damage also results from treatment of forests and rangelands, and even suburban areas, for the control of pests of man and animals.

By nature, honey bees from a colony visit flowers over an area of several square miles. The intensity of visitation in any one part of the area is determined by the relative attractiveness of the flowers. The extent of damage to the colony by a pesticide application is influenced not only by the relative toxicity of the material, the number and methods of application, the time of day, and the weather conditions, but also by the number of bees from the colony visiting the flowers in the treated area, the type of food (nectar or pollen) they are collecting, the type of flowers the food is collected from, the season of the year the damage occurs, and even the influence of forage available to the bees for weeks before and after the application.

Wild bees are also damaged by pesticides. Poisoning may result from contaminated food as well as from florets, leaves, soil, or other material used by the bees in nesting. The toxicity of a specific insecticide to honey bees and wild bees is not always the same, and even among wild bees some materials are more toxic to one species than to another.

The problem of bee poisoning is one of long standing, as pointed out by Shaw (1941) and Todd and McGregor (1952). It became unusually severe in connection with the use of arsenical sprays on fruit in the early part of this century. This resulted in the enactment of legislation in several States, which prohibited the spraying of the trees while they were in bloom. The legislation was beneficial to both the beekeeper and the grower, because of the need for the bees to pollinate the fruit blossoms as well as for the protection of the bees. The legislation alleviated but did not eliminate the damage because of the flowering habits of fruit trees. Some of them blossom earlier than others or stay in blossom longer. When insecticides are applied to safe trees (those that no longer have open flowers), the material drifts to and contaminates nearby flowers (McIndoo and Demuth 1926).

There was another surge of damages when ground and air machines began large-scale applications of calcium arsenate on cotton and other crops (Hawes and Eisenberg 1947) during the 1920's. These applications increased in volume during the 1930's and into the early 1940's, causing great damage to beekeeping (Bertholf and Pilson 1941, Butler et al. 1943, Eckert and Allinger 1935,1936).

This damage subsided during the mid-1940's when growers shifted from the use of arsenicals to DDT (McGregor and Vorhies 1947, McGregor et al. 1947). However, with the development of other chlorinated hydrocarbons, phosphates, and carbamates, the problem increased to an even higher intensity, and considerable study was devoted to the problem (Anderson and Tuft 1952; Anderson and Atkins 1958, 1967, 1968; Anderson et al. 1964; Palmer- Jones and Forster 1958; Todd and McGregor 1961; Weaver 1950,1951).

Severity further increased to the point of disaster for many beekeepers in the late 1960's when usage of DDT and some other chlorinated hydrocarbons was decreased sharply by legislation as a reaction to public concern, and they were replaced in the majority of instances by the more toxic phosphates and carbamates.

The effect of an insecticide application may not be confined to damage to the pollinators of a distant crop or elimination of pollinators for the target crop. Another previously overlooked factor associated with the pesticide may be that it can detract from the plants' productiveness. Beekeepers frequently comment that they believe the pesticide influences the plant itself detrimentally from the bee forage standpoint. This belief has recently received some experimental support. Sedivy (1970) reported that only 10.5 percent of pollen grains germinated after they were dusted with Melipax ⁷ as compared to 62.1 percent in the control pollen. When the pollen grains were treated with 0.3 percent Fribal emulsion, another apparently toxaphenelike compound, only 28.2 percent germinated as compared to 81.5 percent of the control pollen. None of the grains treated with 0.7 percent Fribal emulsion germinated as compared to 79.0 percent of the control.

Gentile et al. (1971) reported that the insecticide naled, at only 100 ppm, completely inhibited germination of both tomato and petunia pollen. They also reported that azinphosmethyl, DDT, dichlorvos, dicofol, endosulfan, and Gardona R caused reduction in pollen germination and/or pollen tube elongation. Carbaryl and methomyl had little or no deleterious effect on pollen, and xylene was noninjurious.

The separation of the toxic or repelling effect of the presence of the insecticide on the plant from the possible less attractiveness of affected pollen is difficult, but the idea merits further examination, both from the effect of pesticides on the plants and on the pollinating insects.

^__________
7 According to J. R. Hanson (personal commun., 1972), Melipax is a toxaphenelike chlorinated camphene, which on bioassy shows about 40 percent less activity than U. S.-made toxaphene.

Numerous surveys have been made to determine the extent of the losses of bees from pesticides. Levin (1970) stated that some 500,000 colonies were killed or damaged in the United States in 1967, of which 70,000 were in Arizona and 76,000 in California. Swift (1969) stated that losses in California in 1968 were even greater--83,000 colonies. Wearne et al. (1970) and Barnes (1972) concluded that the major problem confronting the beekeeping industry was bee losses due to pesticides--with which there is little disagreement by the beekeeping industry. All indications point to an annual loss by the industry in the neighborhood of 10 percent caused by pesticides alone. Few industries can tolerate such losses and survive. The effect of these losses on the adequacy of crop pollination is unknown.

[gfx] PN-3766, FIGURE 30.- Honey bees killed by insecticides.

Wherever pesticides are applied to plants there is a possibility of damage to bees. Because of the volume of insecticides used on cotton and because of the plant's attractiveness to bees over a long period, this crop doubtless holds first rank in the poisoning of bees. The spraying of fruit, particularly apples, but also apricots, cherries, citrus, nectarines, peaches, pears, plums, and prunes, causes serious losses. After the use of DDT on sweet corn was discontinued, the other materials applied on this crop caused serious damage to bees. Increased use of pesticides on soybeans, a relatively new poisoning hazard, is causing increased damage to bees. The treatment of numerous vegetables also causes severe losses in restricted areas.

Control and eradication programs on specific crops or areas, for example, the cereal leaf beetle or the pink bollworm control program, frequently cause unexpected and large losses because of the concentration of material in the areas involved. Grasshopper control programs on rangelands (Levin et al. 1968), gypsymoth control programs in forests, nuisance mosquito abatement programs in moist wastelands, or even suburban areas, and specific mosquito or fly eradication programs, as well as certain herbicides and defoliants (Palmer-Jones 1960), cause the greatest losses (Martin 1970).

INSECTICIDES

Insecticides affect bees in one or more ways as stomach poisons, as contact materials, and as fumigants. Arsenicals are typical stomach poisons, pyrethrum is a typical contact insecticide, and hydrogen cyanide, paradichlorobenzene, and carbon disulfide are examples of fumigants.

Botanicals.--Only a small amount of our insecticides are derived from plants. These sources are cube, derris, nicotine, pyrethrins, ryania, sabadilla, and tephrosia. The bulk of this material is used in households and gardens, and, because of its inaccessibility to bees or the relatively minute amount used, it presents no hazards to pollinating insects. Sabadilla dust is sometimes used on citrus where it can create a bee poisoning problem.

Occasionally, bees are poisoned by feeding on nectar or pollen of certain plants, for example, California buckeye (Aesculus californica (Spach) Nutt.), locoweed (Astragalus spp.), or mountain laurel (Kalmia latifolia L.). Reaction of the bees to these plant poisons can usually be differentiated from those caused by most pesticides.

Inorganics.--These pesticides include arsenicals, fluorides, mercury compounds, and sulfur. The method and limited use of the mercury compounds precludes their presenting a hazard to bees. Elemental sulfur alone or when used with other insecticides in the field, presents only a slight repelling action, although fumes from burning sulfur are highly toxic to insects. Fluorides are rarely used on a large scale and present no problem. In certain sections of Europe, fluoride compounds from smelters frequently cause bee damage. Whenever arsenicals are used they pose a serious threat to bees.

Organics.--The chlorinated hydrocarbons, organophosphates, and carbamates vary in their toxicity to bees from relatively nonhazardous to highly hazardous, depending upon the individual material or combination of materials.

Pathogens: bacteria, protozoans, and viruses.--None of these that are currently recommended or that have been tested for biological control pose a hazard to bees (Cantwell et al. 1972).

DEFOLIANTS, DESICCANTS, AND HERBICIDES

Most tests have shown this class of materials to be nonhazardous to bees, except for their removal of the food source from the plant; however, Morton et al. (1972) reported that paraquat, MAA, MSMA, DSMA, hexaflurate, and cacodylic acid were extremely toxic when fed to newly emerged worker honey bees at 100 and 1,000 ppm concentrations. Although newly emerged bees do not forage away from the hive, they consume food that others bring in. MSMA, paraquat, and cacodylic acid were also highly toxic when sprayed onto older bees in small cages (Moffett et al. 1972).

DILUENTS, SYNERGISTS, AND ACTIVATORS

There is little information on the influence of these agents on the toxicity of the primary pesticides on honey bees. Possibly different interpretations of the effects of certain pesticides may have been associated with the materials with which they were applied.

FUNGICIDES

As used, the copper compounds, mercury compounds, pentachlorophenol, sulfur, and zineb have caused no trouble to bees.

SEX LURES, ATTRACTANTS, AND OTHER HORMONES

These usually cause no problems to bees, and their use near bees is generally welcomed. Occasionally, a few honey bees and bumble bees have been found in traps containing Japanese beetle lures (Hamilton et al. 1970).

BIOLOGICAL CONTROL AGENTS (PARASITIC AND PREDATORY INSECTS)

Beekeepers would welcome biological control of harmful insects on crops because the control agents likely to be used would prey on the specific insects without harming bees. This would permit bees to forage with safety and effectively pollinate the crop.

The majority of poisoning occurs when the bee is in the process of collecting nectar and pollen. In the stomach-poison types of material, the bee is poisoned when the material is ingested with the nectar or pollen. The food may also be transported to the hive where it is fed to and poisons other bees. With some quick-acting poisons, the bee may die in the field. With others, it may return to die in the hive or crawl from the entrance and die nearby. The poisonous material may be obtained from the treated field or it may have drifted from unattractive plants, such as young lettuce or tomatoes, onto attractive plants in bloom such as alfalfa, melons, or flowering weeds.

Bees are also believed to get poison from imbibing water in the form of dew on the plants or from watering places within the treated area, but there is little data to support this.

In the case of nerve-type poisons such as parathion, the bees could easily become poisoned while flying through or over the area while the material in its gaseous form is in the air.

During extremely high temperature, a colony can experience severe loss if the water supply is cut off for only a few hours. If the water supply were so located that the water carriers became poisoned in flight, the colony could suffer both directly in the loss of the water carriers and indirectly from lack of water, even though the pesticide were applied to a totally unattractive crop.

Pesticides applied to plants may get into the nectar directly or reach it indirectly by moving from the treated parts through the plant system (Jaycox 1964, King 1964). The likelihood of bees being killed in economic numbers by the latter method (Johansen et al. 1957) with currently recommended materials is extremely small, and the likelihood of such materials reaching the public in marketable honey is indeed remote.

The various materials can and frequently do reach the hive in pollen that can cause serious poisoning when fed to the developing brood. Pollen gathering is also reduced when the plants are treated (Todd and Reed 1969). This reduction in turn reduces brood production and colony strength.

SYMPTOMS OF BEE POISONING

The individual bee.--Bees react differently to the effect of different insecticides. The symptoms of arsenic poisoning are very pronounced. In the early stages, adult bees become sluggish and soon neglect their duties, so the brood apparently dies of starvation; later, their abdomens become greatly swollen, being filled with a yellowish watery liquid, still later, the legs and wings become paralyzed; and, finally, the bees die in a state of coma. By contrast, the symptoms of bees affected by DDT were described by McGregor and Vorhies (1947): "They acted as if cold, lighting on leaves, twigs, or lumps of soil, selecting warm spots, and generally sitting motionless unless disturbed. Sometimes they fell from these perches, then revived and departed slowly, as a cold bee does, or in rapid erratic flight to alight again a few yards away. In crawling they were much slower than arsenic poisoned bees. After becoming unable to crawl they would be helpless, sometimes for hours if protected from direct sun. They often lay on their backs or sides making feeble movement with legs or antennae."

Other materials affect bees other ways. When bees are exposed to the insecticide BHC, for example, they are much more inclined to sting.

The cluster.--Usually, the first noticeable effect of insecticide poisoning on the colony is recently dead or dying bees on the ground near the hive entrance, although this is not always the case. If poisoning is severe, the affected or dead bees will accumulate on the floor of the hive faster than the normal bees can remove them.

Flight from the entrance decreases and fresh nectar can no longer be shaken from the brood combs. As the cluster population decreases, its size and the concentration of bees within it also decreases. The brood is gradually abandoned, the smaller larvae begin to die, and many of the larger larvae crawl from their cells and fall to the floor of the hive before they die. The sealed brood begins to die and as it does so the color of the capped cells becomes darker.

As the cluster continues to diminish and become disorganized, the combs in colonies exposed to the hot sun begin to melt. Soon the liquid honey begins to ooze from the hive entrance and spreads among the dead bees on the ground. Frequently, the last individual to die is the queen. Wax moths quickly discover the deserted colony, lay their eggs within it, and the developing larvae soon riddle and destroy the remaining combs.

Bees frequently store contaminated pollen in the combs, for example, pollen collected from corn sprayed with carbaryl. This contaminated pollen remains toxic for months, even in combs removed from weakened or destroyed colonies. If such pollen-filled combs are placed on nonpoisoned colonies, the pollen may cause serious poisoning to the young larvae to which it is fed.

Poisoning may result in complete destruction or the colony may be weakened to varying degrees. If it is exposed to a single application that does not destroy it, the field force may be lost, but if it has a large amount of brood emerging its apparent recovery is rapid. More severe poisoning may prevent rapid buildup, and the colony may go into winter without adequate reserves of food or young bees. Such colonies may die or survive the winter in such a weakened condition as to be of no value for much of the following year.

The grower is sometimes confused when he is told that colonies have been damaged by pesticides yet he sees apparently normal bees entering and leaving the hive entrance. He may be influenced by the fact that young bees take their orientation or "play" flight near the entrance before they reach the foraging age. This can give an impression of great activity when no food is being stored. Also, the difference between colony survival and a surplus honey crop may be the loss of only a few thousand bees, which only an experienced beekeeper can detect.

DIFFICULTY IN ESTABLISHING DEGREE OR PROOF OF DAMAGE

Beekeepers sometimes want to establish that the bees have been damaged by a pesticide, or establish the degree of such damage. To do so is extremely difficult, even if the colony is completely destroyed.

If destruction occurs just before a honey flow no honey is stored, and all the labor and expense of care and maintenance of the colony at its appropriate strength in anticipation of the flow is lost. Destruction a few weeks later might leave the hive with considerable stores of honey that could be salvaged.

If the colony is not completely destroyed, again the time of damage influences the degree of loss. Removal of a few thousand field bees from a strong colony cannot usually be detected by the average beekeeper, yet this loss just before a honey flow may result in no surplus honey storage for the beekeeper. The same loss a few weeks later might have no economic significance on current production. It could, however, affect the overwintering ability of the colony.

Honey bees, like range cattle, need not be under daily surveillance by the owner. In both cases, the owner knows the critical periods in the life and growth of each, and observations and management are timed accordingly. Manipulating honey bee colonies daily is detrimental. The beekeeper knows through experience when honey flows are expected. He manipulates the colony to its major strength at the appropriate time, gives it the anticipated storage area needed, then leaves it undisturbed, sometimes for a few days, at other times for several weeks.

For these reasons, the beekeeper may not know when the bees are damaged. If only the predominant field force is destroyed, and there is no accumulation of dead bees at the entrance, the number of house bees remains relatively constant. An examination of the colony by an expert beekeeper might fail to detect the loss of bees. Only if he knows the normal rate of honey storage for this particular time and location, and recognizes that normal storage has ceased, can the effect be recognized.

Determining the source of the pesticide is even more difficult. If more than one field is treated on the known day of damage, or if numerous fields in the area are receiving periodic treatments, the beekeeper frequently has no way of determining in which area the bees are foraging and the source of damaging material.

If there is only one major source of nectar in the area (and only the experienced beekeeper can determine this), and if only one field from which this nectar is derived is treated on the day the bees show serious poisoning symptoms, the deduction can be drawn that the particular field is the source of damage.

CHEMICAL ANALYSIS

The bees, themselves, are more frequently affected than are either the nectar or the pollen. An identification of the material on or in the bees, if identical with the material known to be applied to the field, is a strong inference as to the source of the material. However, many pesticides break down rapidly when exposed to the elements or the samples taken by the beekeeper for analysis are otherwise not properly handled.

For chemical identification, the sample for analysis should be collected immediately after exposure and kept frozen until analyzed. Even with these precautions, the analysis may not reveal the identity of the material.

There is no Federal laboratory equipped for routine analysis of bee samples for all pesticide residues. Some State experiment stations are equipped to determine certain residues. Some commercial laboratories analyze for residues for a fee. If analysis of the bees is desired, the analyst should be consulted before the sample is submitted to determine if the analysis can be conducted, and the best method for taking the samples.

SUGGESTIONS FOR REDUCING BEE LOSSES

Grower action.--Because of the value of bees to agriculture as pollinators, the grower should become well informed about them and about the relative damage of different pesticides to them. This will help him to take practical steps to avoid damage to bees. The grower can take numerous steps to prevent or alleviate this damage. It is in his interest that this be done.

The grower can prevent the treatment of many plants when they are in bloom, or he can arrange for the treatment to be made at the time of day or period in the plant's growth when the bees are not visiting it. He can also have the material applied in the form or manner that would cause the least damage. He can choose between materials that vary in toxicity to bees and use the one least toxic.

Control methods other than the use of harmful chemicals can also be considered by the grower. These methods include biological, cultural, and integrated control as well as the use of field sanitation, crop rotation, and resistant varieties. These offer the greatest safety to bees. Their use, as compared to the broad spectrum insecticides, would permit maximum use of bees as pollinators.

Finally, the grower can become acquainted with the beekeepers and the apiary locations in his area. Then when the use of materials highly toxic to bees is anticipated, he can notify the beekeeper so that protective steps may be considered.

Beekeeper action.--If the apiary is a permanent one, the beekeeper should let nearby growers know where it is located. If this is impractical, the beekeeper's name, address, and telephone number should be prominently posted in the apiary so that it can be obtained without danger of bee stings. Registered brands on the hives is another way of establishing ownership. This is useful only if the brand is known locally by officials who can release such information.

Beekeepers frequently state that the only solution to the bee poison problem is to go out of business. Usually, moving colonies to escape damage from pesticides is equally unsatisfactory. The reluctance of beekeepers to move an apiary is frequently not understood and treated as recalcitrance on his part. With the best knowledge and care, the colonies at times are likely to be completely destroyed if certain insecticide material is to be applied to a nearby crop. When such is the case and removal of the colonies is the only recourse, why is the beekeeper hesitant to move or why does he sometimes leave the colonies in the area? A considerable amount of beekeeping knowledge is involved in his decision.

The colonies may contain new combs filled with honey that will break under vibration by the truck that hauls them over rough roads. Should this occur, the bees in the cluster will be drowned by the honey and the combs lost.

Dependable safe alternate locations are difficult to find. Furthermore, maintaining such locations, including a road to them, rental, shade, and other factors make them expensive insurance.

No beekeeper can determine the value of a bee location merely by looking at it. Each must be proven by test as to its productiveness, safety, and dependability. When a beekeeper moves an apiary to a new location, he must become acquainted with a new ecological environment, including flora, fauna, soil, geography, water, rainfall, wind directions, velocity, and scores of other interrelated factors. When the colonies are moved to the new location, therefore, they may suffer from lack of water or from flooding, the colonies may become overgrown with weeds or shrubs, or suffer from lack of shade. The plants may not yield an adequate source of food and the colonies starve, or they may yield at an unsuspected time and cause excessive swarming and the colonies deteriorate.

If the beekeeper does not move, he should become acquainted with the crops in the area, the pesticides recommended, and the period of the year when the pests are likely to require control measures. He should also be acquainted with the relative toxicity of the pesticide materials so that if he is notified of a pending treatment he can anticipate the outcome.

The colonies should be kept in the best condition practical, because a strong broodnest will provide rapid replacement of field bees. Shade for colonies under hot weather conditions has proven quite beneficial (Owens 1959). An ample supply of clean unpolluted water should be nearby so the colony will not suffer for lack of it if many of the field bees are destroyed. There should be ample space within the hive for normal growth and expansion. The colony should be headed by a young, vigorous queen so that maximum broodrearing will be maintained, with the food supply and colony strength permitting.

When the beekeeper knows in advance that a short-residual but highly toxic insecticide is to be applied shortly after dawn on a nearby crop, the colonies may be confined until the danger of the pesticide is past (Jaycox 1963). One method of confinement when the temperature is high is to cover the colonies before dawn with a blanket of burlap. This should be kept moist (Owens and Benson 1962) as long as the bees are confined. If the temperature is not high, the bee colony entrance may be blocked before flight begins, then opened as soon as danger of the insecticide is past.

Even when the colonies are not moved, something may occur that alleviates or prevents insecticide damage. The grower may decide that treatment is unnecessary or at the last minute he may be prevented by weather or other factors from applying the material. The bees may fail to visit the field, or the damage suffered may be less severe than anticipated. Subsequent honey production may counteract the damage. Frequently, a beekeeper moves, only to have the colonies destroyed by pesticides in the new location.

Because of all of these factors, many beekeepers realize that moving is as much a gamble as remaining near the pesticide-treated area.

State or Federal action.--The 91st Congress enacted provisions for indemnification payments to beekeepers for losses sustained from pesticides (U.S. Congress 1970). A major problem in carrying out the purposes of this bill concerned the just and adequate compensation for losses sustained and the establishment of acceptable proof of degree of such loss. Because there is little reciprocal benefit from indemnification payments, this would not appear to be a long-term satisfactory solution to the bee poison problem.

Research on bees and their relationship to pollination is beneficial to both the beekeeper and the grower. The new knowledge may concern the bee itself, including its behavior, breeding, management, or nutrition, or it may concern the value of the bee to the crops. In either instance, the new information is permanent and beneficial to both groups.

The information on the relative danger of pesticides to bees and on the value of the bees to the crops can be released to growers and beekeepers at opportune moments when it is of most usefulness. In addition, grower- beekeeper meetings can be sponsored in which each learns of the problems of the other and the need for cooperation.

Hundreds of pesticides have been tested as dusts or sprays for their relative degree of hazard to bees. These tests have been summarized on numerous occasions but recently by Anderson and Atkins (1968), Anderson et al. (1971), Atkins et al. (1970), and Johansen (1969). Table 4, ⁸ taken from Anderson et al. (1971), shows the relative toxicity of numerous materials determined by laboratory and field studies. The hazards to wild bees through poisoning of the leaves used for nest building (Waller 1969) as well as through their food or contact was summarized by Johansen (1969) and is presented in table 5.

Additional studies on effect of herbicides by Moffett et al. (1972) showed that cacodylic acid, MSMA, and paraquat were highly toxic when sprayed on honey bees in small cages. When fed to newly emerged worker bees, the following materials were relatively nontoxic: 2-chloroethyl-phosphonic acid; 2,3,6-TBA; 2,4-D; 2,4-DB; 2,4,5-T; chloramben; dalapon; dicamba; EPTC; Ethrel R; picloram; and silvex. The following were extremely toxic at concentrations of 100 parts per million by weight: cacodylic acid, DSMA, hexaflurate, MAA, MSMA, and paraquat.

These herbicide tests have shown that some materials considered safe by the previously mentioned short-term cage tests with dust were indeed highly toxic when tested by other methods. They also indicate that the toxicity of materials cannot be predicted and that the toxicity may vary according to methods of application and other factors.

__________
⁸ Tables 4 and 5 are reprinted essentially as they appeared in their original form.

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______and ATKINS, E. L., JR.
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______ ATKINS, E. L., JR., TODD, F. E., and others.
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______and ALLINGER, H. W.
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______1964. EFFECT ON HONEY BEES OF NECTAR FROMSYSTEMIC INSECTICIDE-TREATED PLANTS. Jour. Econ. Ent. 57: 31 - 35.

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______COFFEY, M. D., and QUIST, J. A. 1957. EFFECT OF INSECTICIDE TREATMENTS TO ALFALFA ON HONEY BEES, INCLUDING INSECTICIDAL RESIDUES AND HONEY FLAVOR ANALYSES. Jour. Econ. Ent. 50: 721 - 723.

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______FORSYTH, W. B., FAIRBROTHER, G. L., and SKINNER, F. B.
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______CASTER, A. B., and FROST, M. H., JR.
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MCINDOO, N. E., and DEMUTH, G. S.
1926. EFFECTS ON HONEYBEES OF SPRAYING FRUIT TREES WITH ARSENICALS. U.S. Dept. Agr. Dept. Bul. 1364, 32 pp.

MOFFETT, J. O., MORTON, H. L., and MACDONALD, R. H.
1972. TOXICITY OF SOME HERBICIDAL SPRAYS TO HONEY BEES. Jour. Econ. Ent. 65: 32-36.

MORTON, H. L., MOFFETT, J. O., and MACDONALD, R. H.
1972. TOXICITY OF HERBICIDES TO NEWLY EMERGED BEES. Environmental Ent. 1: 102-104.

OWENS, C. D.
1959. SHADE FOR BEES. Amer. Bee Jour. 99: 481 - 482.

_____and BENSON, C. E.
1962. CONFINING HONEY BEE COLONIES WLTH BURLAP. Amer. Bee Jour. 102: 260 - 262.

PALMER JONES, T.
1960. EFFECT ON HONEY BEES OF SOME CHEMICAL WEEDKILLERS. New Zeal. Jour. Agr. Res. 3: 485-490.

______and FORSTER, I. W.
1958. AGRICULTURAL CHEMICALS AND THE BEEKEEPING INDUSTRY. New Zeal. Jour. Agr. 97: 298 - 304.

SEDIVY, J.
1970. [THE INFLUENCE OF TOXAPHENE INSECTICIDES ON THE POLLEN OF LUCERNE.] Ochr. Rost. 43(3): 187 - 190. [In Czech., English summary. ] AA-805/71.

SHAW, F.R. 1941. BEE POISONING: A REVIEW OF THE MORE IMPORTANT LITERATURE. Jour. Econ. Ent. 34: 16 - 21.

SWIFT, J. E.
1969. UNEXPECTED EFFECTS FROM SUBSTITUTE PEST CONTROL METHODS. Biological impact of pesticides in the environment. Symposium, Aug. 18-20, Oreg. State Univ., Corvallis, 16 pp.

TODD, F. E., and MCGREGOR, S. E.
1952. INSECTICIDES AND BEES. U.S. Dept. Agr. Yearbook 1952: 131-134.

______ and MCGREGOR, S. E.
1961. INSECTICIDES AND HONEY BEES. U.S. Dept. Agr. Yearbook 1961: 247-250.

______and REED, C. B.
1969. POLLEN GATHERING OF HONEY BEES REDUCED BY PESTICIDE SPRAYS. Jour. Econ. Ent. 62: 865-867.

UNITED STATES CONGRESS.
1970. AGR. ACT OF 1970. INDEMNIFICATION FOR BEEKEEPERS. In P.L. 91-524, p. 24, 91st Cong. HR 18546, Sec. 804.

WAILER, G. D.
1969. SUSCEPTIBILITY OF AN ALFALFA LEAFCUTTING BEE TO RESIDUES OF INSECTICIDE ON FOLIAGE. Jour. Econ. Ent. 62: 189-192.

WEARNE, R. A., BERGMAN, P., GIBBS, L. C., and others.
1970. BEE LOSSES--THE IMPACT ON POLLINATION-- HONEY PRODUCTION. U.S. Dept. Agr. Ext. Serv., 12 pp.

WEAVER, N.
1950.TOXICITY OF ORGANIC INSECTICIDES TO HONEYBEES: STOMACH POISON AND FIELD TESTS. Jour. Econ. Ent. 43: 333-337.

______ 1951. TOXICITY OF ORGANIC INSECTICIDES TO HONEY BEES: CONTACT SPRAY AND FIELD TESTS. Jour. Econ. Ent. 44: 393 - 397.

[gfx] TABLE 4--Relative toxicity of pesticides to honey bees as determined by laboratory and field tests in California, 1950-71 (Source: Anderson et al. 1971).

See footnotes at end of table.

[gfx] TABLE 4.--Relative toxicity of pesticides to honey bees as determined by laboratory and field tests in California, 1950-71 (Source: Anderson et al. 1971)--Continued

[gfx] TABLE 5.--Wild bee poisoning hazard of insecticides on blooming crops (Source: After Johanson 1969)