by C. L. Farrar
Entomology Research Division, Agricultural
Research Service, U.S.D.A.(1)
The beekeeper must recognize that Federal food-additive laws now in effect apply to honey as well as all other foods. The large purchasers of honey are requesting suppliers to certify that the honey offered for sale is pure and free of contaminants. Honey, like any food product offered for sale, can be condemned if it contains even traces amounting to less than 1 part per million of a chemical, drug, or antibiotic for which no legal tolerance has been established. One publicized condemned shipment could do great harm to the entire honey market. This situation need not cause a panic in the beekeeping industry, but it does require caution and good judgment in how chemicals and medicants are used.
Many beekeepers think the food-contamination problem centers on the use of sulfa compounds and antibiotics for the control of bee diseases. These are important, but when used with discretion they probably present less of a problem than carbolic acid used for the removal of honey, calcium cyanide used for killing colonies before extracting the honey, and the fumigation of comb honey.
Most of the materials in question are needed for profitable beekeeping management. Experience has shown that they can be used safely for the purpose intended provided they are employed at the right time, by the right method, and at the correct dosage. However, meeting the legal requirements with respect to residues is a matter of special importance. Precautionary recommendations are presented here as a guide in the use of the principal chemicals and medicants employed in beekeeping practices. The recommendations will be subject to change as more specific information on each becomes available.
Sulfathiazole, streptomycin, dihydrostreptomycin, terramycin, fumagillin, and similar materials should be used primarily as disease preventives. These medicants also have value in eliminating active infections. The distinction between disease prevention and disease control is in the degree of colony infection. For disease prevention, they are directed against the infections that are not detected by inspection and before the pathogens have a chance to increase. However, preventive treatment should not be substituted for careful and frequent inspection of all colonies for disease. Any medication that does not prevent disease from developing in good colonies during a 2- to 4-week spring treatment should be considered ineffective and its use discontinued.
Medicants should be used only on vigorous colonies. Inferior colonies – colonies without vigorous brood production due to the queen, populations, or lack of pollen – will not clean up all the infected brood that may be present. Treatment of weak colonies usually results in a temporary check on the disease.
The medicants should be used early in the spring at least one month ahead of the surplus honeyflow. The reason for early-spring preventive treatment is to avoid loss of brood or bees from disease and provide ample opportunity for the colony to consume all medicated stores well in advance of the honeyflow. Preventive treatment should be used in apiaries having a previous record of disease or in those located where disease has been present in other apiaries within flight range.
There are three general methods of applying medicants: (1) gorging the bees by pouring medicated sirup over the clusters; (2) mixing the medicant with powdered sugar and dusting it over the clusters; and (3) bulk-feeding the medicated sirup by use of feeder pails, division-board feeders, or filling combs with sirup. All the medicants can be included in pollen supplement. The choice of method can affect the success of treatment. It is necessary to know the disease you are applying treatment against and the characteristics of the medicant that influence its effectiveness.
The gorging method provides good dosage control and the medicated sirup will be distributed in and around the entire brood nest, where it will be used immediately by the colony. The medicants should be added to heavy sugar sirup (2:1) because it prolongs their availability. Two additional treatments at 4- to 5-day intervals are necessary to enable the bees to clean up any infected larvae that may be present while protecting against further spread of disease. The procedure is to pour about 1 pint of the medicated sirup over each cluster, leaving the cover off as each colony is treated; then return to the first colony and add a similar quantity of sirup, replacing the cover. Continue with successive colonies until all have received as much sirup as the bees will clean up. The amount to pour at one time will depend on the number of bees in the colonies, but use the maximum that will not cause an excess to run out the hive entrance.
The dusting method does not permit good control of the amount of medicant each bee receives. It has been commonly used but provides uncertain distribution of the medicants through the brood nest and some are toxic above certain dosage levels. Thus, the dusting method introduces many elements of chance in dealing with disease problems. Beekeepers can ill afford to take chances with methods that require prolonged treatment to eliminate disease. To do so increases the chance of contaminating the surplus honey, increases cost of labor and materials, and reduces the strength of colonies.
Bulk feeding does not provide the best distribution of medicated sirup in the brood nests of strong 2- and 3-story colonies, but it is satisfactory for disease prevention in package colonies or for fall feeding after the colonies or for fall feeding.
The incorporation of medicants in the sirup used for mixing pollen-supplement cakes is recommended for disease prevention where the colonies are sufficiently strong to consume 1 to 3 pounds of supplement per week.
All medical agents should be accurately weighed to provide exact dosage control. Dosages are given in milligrams or grams because the amount required per colony or volume of sirup is too small to weigh in ounces. A balance scale weighing in grams is a necessity for proper use of medicants in apiary management, unless sufficiently large quantities are used at one time to employ scales weighing in ounces. One milligram equals 1/1000 gram, one gram equals 1/28.4 ounce, and 1 ounce equals 28.4 grams. If necessary, have your druggist weigh the amount you need. Use of a crude measure, such as a spoonful, may fail to control the disease or the treatment may prove toxic to the bees.
In most states official apiary inspectors are required to burn all colonies infected with American foulbrood. The state laws are designed for the protection of the beekeeping industry. Beekeepers employing therapeutic medicants should encourage full enforcement of their state inspection and disease-control laws. The presence of disease in any apiary is a menace to other beckeepers and an indication that the owner is not using proper control measures.
Inspect colonies frequently and comply with your state laws pertaining to this disease. Preventive treatment is desirable early in the spring for all colonies in apiaries having a record of American foulbrood or in areas where this disease has been known to exist. Use 1 gram of sodium sulfathiazole per gallon of 2:1 sugar sirup (1 oz. sulfa/30 gals. sirup) applying three gorging treatments at 4- to 5-day intervals; also incorporate the same medicated sirup in preparing any pollen supplement.
Three dusting treatments with 160 milligrams of terramycin in powdered sugar during a 2 weeks’ period have also been reported effective. The Terracon preparations TM-25, TM-10, and TM-5 provide 25, 10, and 5 grams of terramycin, respectively, per pound of Terracon. To provide 160 milligrams of terramycin, mix 1 part of TM-25 with 4 parts of sugar and apply 1/2 ounce of the mixture per colony at each treatment (for TM-10 use 1 part to 2 and apply 3/4 ounce or for TM-5 use equal parts and apply 1 ounce). Soluble terramycin (TA-FSP-25) has been recommended at 54 milligrams per treatment.
European foulbrood has become a serious disease in the last 10 years. There is evidence that it was far more prevalent during the two preceding decades than beekeepers realized. For many years it attracted little attention because diseased larvae were seldom seen. We now know that considerable brood was lost, but it was cleaned out by the bees before the symptoms of European foulbrood could be recognized. Colonies with low-quality brood that is not due to poor queens, pollen deficiency, or similar factors respond to medicants that are effective against the virulent form of European foulbrood.
Streptomycin sulfate or dihydro-streptomycin sulfate at a concentration of 0.6 gram (600 mg.) per gal-lon of 2:1 sirup (2 oz./100 gals.) in three applications during a period of 2 weeks by the gorging method has proved most effective in the prevention or control of European foulbrood.
Terramycin has also proved effective but is somewhat slower in action than streptomycin. This may be due to its use as a dust or to the great variation in dosages that have been recommended. Terramycin is relatively unstable in solution and has generally been applied as a dust.
This disease of adult bees probably takes a greater toll of the productive capacity of honey bees than do the brood diseases. Nosema is so wide-spread we must presume that every colony has some infected bees. The infection level may range from less than 1 to 100 percent. Nosema shortens the life of bees by about one-half. The most important means of control is good colony management, which provides conditions that are favorable for brood rearing to add young bees to the colony faster than the infection spreads within the population. Losses from Nosema are most conspicuous in colonies started with package bees, in nuclei, and other weak colonies.
The antibiotic fumagillin is effective in preventing Nosema from spreading within a population and in reducing queen supersedures due to the infection of the queen: One gallon of 2:1 sirup containing approximately 5 grams of Fumidil B (100 mg. fumagillin) should be fed to package colonies when they are installed in the hive. The product Fumidil B is packaged specifically for bee feeding with directions for its use, and each gram contains 20 milligrams of fumagillin. Nuclei should be fed the same concentration of fumagillin in all sirup they require.
Carbolic Acid Boards
The common practice of using carbolic acid in removing bees from supers probably presents a greater food-contamination hazard than do the medicants. A safer method is urgently needed. If you use carbolic acid, exercise the following pre-cautions: (1) Use this method only for removing sealed honey and under conditions that will permit the bees to be driven off the combs in 2 to 3 minutes; (2) make sure the cloth is well separated from the super by use of a deep rim; (3) use chemically pure carbolic acid; (4) use it sparingly; (5) stand the supers on end when they are set off the hive to obtain maximum ventilation before loading, but use due precaution under conditions that would cause robbing; and (6) stack the supers for good ventilation in a hot room equipped with an adequate exhaust fan and delay extracting until all odor of carbolic acid has been removed.
Calcium Cyanide for Killing Colonies
Do not apply calcium cyanide or any other poison with a dust gun to colonies from which honey is to be removed for extraction. If you do use cyanide, place it on papers on the bottom board and on top of the hive under the cover, and when removing these papers containing the cyanide residue be careful not to spill any on the combs. It would be safer to remove all supers to be extracted before killing the colonies.
Fumigation of Comb Honey
Place the fumigants in shallow receptacles on top of the supers for evaporation, since the gases are generally heavier than air. Do not pour or discharge a fumigant directly onto the honey. Follow all precautions specified for handling a particular fumigant and ventilate the super thoroughly after fumigation.
Extracting Honey from Brood Chambers
The practice of extracting honey from brood chambers, which is used in some areas, will increase the chance of contaminating honey with medicants that have been fed. Under such conditions special caution in use of medicants should be exercised. Well-managed strong colonies with large honey reserves will consume several times as much honey, but they will produce a surplus two to five times greater than small colonies kept on bare subsistence rations. More often, use of brood nests larger than are employed under some systems of management will increase the size of the surplus crop. Thus, it may be false economy to extract honey from the brood chambers to reduce the weight for moving.
The beekeeping industry must accept the responsibility of managing so that honey contamination will not occur. This will necessitate the utmost caution in how, when, and at what concentrations beekeepers use chemicals, drugs, and antibiotics.
(1)In cooperation with the Wisconsin Agricultural Experiment Station.
REPRINT FROM AMERICAN BEE JOURNAL – vol. 100 – Number 5 – May, 1960, pages 192, 193