Like most living things, honeybees can become diseased. The most common bee diseases in the United States are American foulbrood (AFB) and European foulbrood, which affect the brood. Nosema is the most serious ailment of adult bees.
In some areas, systematic applications of antibiotic chemicals during spring and fall hive examinations are used to prevent American and European foulbrood (Table 2). Terramycin mixed with sugar has given effective disease control. After checking the brood frames and replacing them, sift the sugar-chemical mixture over the top of the brood frames. Terramycin controls both American and European foulbrood. Although American foulbrood can be cured, present bee laws require that bees infected with AFB be destroyed. The drug is to be used only as a preventive treatment.
Terramycin can be obtained from bee supply houses listed in bee magazines. Terramycin-sugar mixture costs about 10 cents per treatment.
Nosema, a disease caused by the protozoan Nosema apis, attacks the true stomach and intestines of adult bees. It is widespread and especially troublesome in colder areas where winter is long with only a few flight days. The disease is most common during periods of cold damp weather in late winter and early spring. Sick bees with swollen abdomens crawl about quickly in front of the hive, climb grass blades, and try to fly. Often this disease clears up as the nectar flow begins, but its cure and prevention can be brought about by feeding the bees syrup containing the antibiotic fumagillin (Fumidil-B). Prepare the syrup by bringing five to six gallons of water almost to a boil. Remove from the heat and add 1/2 gram of fumagillin. Stir until the fumagillin is dissolved. Then add 10 pounds of sugar and stir to make a clear syrup. The syrup is fed in the fall or in both fall and spring.
DO NOT FEED MEDICATED SYRUP DURING OR RIGHT BEFORE NECTAR FLOW.
The presence of trembling bees with shrunken abdomens in front of or in the hive is an indication of paralysis. These bees resist being driven off by their healthy sisters. Sick bees might also be weak, dark-colored, and shiny. There is no sure cure for this disease, but it does not occur often. One treatment is to requeen the colony if the problem persists. Another treatment is to exchange the colony's position with that of a strong colony.
The mite, Acarapis woodi, is a serious and growing problem for beekeepers. The microscopic mite clogs the breathing tubes of adult bees, blocks oxygen flow, and eventually kills them. Also called acarine disease, this condition affects flight efficiency and results in a large number of crawling bees unable to fly. The inability of bees to fly means a loss of field bees and lack of food in the colony. Another symptom is the abnormal "dislocated" position of the wings of walking bees. The life-span of these infected bees is shortened.
High levels of colony infestations can cause significant economic damage, decreased honey and brood production, increased winter deaths of individual bees, and reduced spring buildup of colonies. Acarine disease could persist in the colony for years causing little damage but when combined with other diseases and unfavorable conditions, the disease increases the mortality of colonies.
Menthol pellets provide control of tracheal mites. A screen package containing two ounces of menthol is placed in each hive in the apiary where tracheal mites are found. Treatments should be placed on the bottom board during hot weather (>80oF) and on the top bars when maximum daily temperatures are cooler than 60oF outdoors. Mite control with menthol is not as effective during cool or cold winter weather. To prevent honey contamination, treat before honey production begins in the spring or after surplus honey is removed in the fall.
An alternative to the menthol treatment is a vegetable shortening/powdered sugar treatment. One part vegetable shortening is mixed with two parts powdered sugar. One cup of this mixture is flattened between two pieces of wax. The patty must be flat enough to fit between the upper and lower brood chambers. If no nectar flow is occurring, feed colonies a light syrup (one part sugar to three parts water) to stimulate heavy brood production. A large population of young bees is needed for successful wintering.
Lines of bees with resistance to the tracheal mite are commercially available. Hives can be requeened with mite-resistant queens. Mite resistance means mites develop more slowly in these bees, but the bees are not immune. Even these resistant bees can succumb to tracheal mites if no other management practices are used.
The mite, Varroa jacobsoni, is one of the most serious pests of the honeybee. It is a parasite that attacks both brood and adults. Unless special measures are taken to search for the mite, early detection is unlikely. The mites develop in sealed brood cells. Bees emerging from infested cells are often deformed with missing legs or wings. Heavy infestation of several mites per cell kills the developing pupae.
Adult female mites are reddish brown to dark brown, oval and flattened in shape, approximately 1/25-inch long and can be seen easily with the unaided eye. Adult male mites are much smaller and lighter. Their flattened body allows them to hide between the bee's abdominal segments or between body regions where they feed on the bee's blood.
Female mites enter honeybee brood cells shortly before cells are capped, feed on the larvae, and lay eggs. Adult mites develop in six to 10 days and mate in the cells before emerging with the bee. Male mites die soon after mating. During spring and summer most mites are found on the brood (especially drone brood). In late fall and winter most mites are found on the adult workers.
Unchecked infestations can kill colonies in as few as three years. Colonies infested with varroa mites can be treated by means of Apistan strips. These strips are available from most beekeeping supply distributors. Remove honey supers and place two Apistan strips in the brood area of the hive. Follow label directions carefully.
The bee louse, Bracula coeca, resembles the varroa mite in size and color. However, the bee louse is an insect with six legs which extend to the side. The varroa mite has eight legs that extend forward. The bee louse never builds up to high enough numbers to cause problems.
Wax moths get in hives in which they can cause damage because the colony is not strong enough to protect the comb or too many empty supers are on the hive. Wax moths also damage unprotected combs in storage. Fumigation with paradichlorobenzene protects combs in storage from wax moths. Combs containing honey must not be fumigated because paradichlorobenzene is readily absorbed by honey.
When fumigating with paradichlorobenzene, stack supers in storage as tightly as possible. No more than five full-depth or 10 half-depth supers should be in a stack. For long periods of storage, seal the cracks between the supers with tape, particularly the bottom of the stack as the gas is heavier than air. Place six table-spoons of crystals on a piece of cardboard on the frames of the top super and replace the cover. Penodically examine the crystals and replace if no longer present. Air out fumigated combs a few hours before returning them to the colonies.
When bee colonies are bothered by wax moths or other insect pests, such as wasps or ants, it usually means the colony is weak. Building up colony strength allows the bees to repel these pests. Skunks might snoop around a hive at night and can weaken a colony by eating bees that come out to investigate the disturbance. If the problem is bad, trapping or poisoning the skunks is necessary.
Mice might nest in combs in winter storage. They also enter hives in late fall and build nests. Colonies can be protected by placing 3/8-inch wire mesh across the entrance. The mesh does not hamper movement of bees in and out of the hive.
An important consideration when locating a colony is the possibility of poisoning by pesticide applications. This is especially true when colonies are located near cultivated crops. The best rule of thumb is to establish and maintain communication with nearby farmers so you will be notified before pesticide applications. The key to protecting bee colonies is prevention, usually possible through cooperation between the beekeeper and those who might apply pesticides.
Cooperative growers concerned about preventing bee losses can follow the these rules: (1) do not apply insecticides to open blossoms; (2) spray preferably in the late afternoon or early in the morning as your second choice--not in the middle of the day when bees are flying; (3) use sprays instead of dusts for a given insecticide; (4) give advanced warning of the use of insecticides so hives can be moved out of the flight range of the danger; (5) apply proper dosages and follow pesticide label directions. Orchardists can reduce bee losses by mowing or clipping blossoms from cover crops before pesticide applications. Beekeepers should be familiar with commonly used insecticides and their toxicity to bees. Beekeepers also should know as much as possible about the relationship of their bees to nectar and pollen plants in the area.
A noticeable symptom of poisoning is a large number of dead bees near the hive. If many bees are killed in the field, there simply might be a lack of bees in the hive. Before bees actually die from most pesticides, they might behave erratically and unusually or become stupefied and paralyzed.