Adult bee diseases are not a threat in this country, except for nosema disease. In some foreign countries, acarine disease poses a potential threat to beekeeping.

Nosema Disease

Cause

Nosema disease is caused by the protozoan Nosema apis. The spores of the disease are ingested by the adult bee where they germinate and multiply in the gut.

Effect

Nosema disease decreases the effective life span of adult workers and, therefore, results in a decrease in the honey harvest. Infected queens are often replaced if their egg laying capacity is affected by nosema disease. Losses in the adult population can indirectly result in neglected brood.

Nosema disease is most prevalent in the spring. This is a time when a dysenteric condition tends to be present in the colonies. In such cases nosema disease poses a serious threat. Mixed infections of Nosema apis and the amoeba organism, Malpighamoeba mellificae, are believed to be more serious than either parasite alone.

Symptoms

A microscope is required to detect the spores of Nosema apis. The best time for finding spores of the disease is the beginning of the flying season after winter confinement. During the summer months it is difficult to find spores in the bees. A small increase of bees infected by the disease may be found in the fall.

No single symptom typifies this disease. Affected bees make trembling movements and their wings become unhooked. Unable to fly, these bees crawl about at the entrance to the colony.

Sending Diseased Samples For Diagnosis

It is sometimes difficult to make a definite diagnosis of diseased brood and honey bees in the apiary. Diagnosis in the laboratory is a service made available to beekeepers and State apiary inspectors by the U. S. Department of Agriculture.

When you select a sample of the comb for laboratory examination for brood diseases, cut a 4-inch-square section of the comb. Make sure this piece of comb contains as much of the dead or discolored brood as possible.

If you suspect an adult bee disease, send at least 200 sick or recently dead bees in the sample. Pack this sample in a wood or strong cardboard box. Do not pack samples in tin or glass containers, and do not wrap either the comb or bees in waxed paper or aluminum foil.

Send all samples to the Bio-environmental Bee Laboratory, Agricultural Research Center, Beltsville, Maryland 20705. Print or type your name and address on the return label and include your Zip Code number.

The abdomen of an infected bee is often distended and appears shiny. The individual circular constrictions of a healthy bee's midintestine are visible, but in infected bees the midintestine may be swollen and the constrictions not clearly visible. (See fig. 7. )

Spread

Nosema disease can be transmitted in several ways. In overwintered colonies, confined bees infected with nosema may defecate on the combs, causing healthy bees to become infected as they clean the combs in the spring. Food stores and soiled shipping cages can also be sources of infection.

Control

The antibiotic fumagillin (Fumidil-BR) has been used for the control of nosema disease. Labels for drugs carry specific instructions for their application, subject to State laws and regulations. Consult with State apiary inspectors, extension apiculturists , or State entomologists before using any chemicals.

Treatment. -To decontaminate solid bee equipment heat the equipment at 120° F. for 24 hours. This treatment will either destroy the spores or make them nonviable.

Take the following precautions when you give your equipment a heat treatment;

Figure 7. Top: Digestive tract from a healthy bee. Note the individual circular constrictions on the ventriculus. Bottom: Digestive tract of a honey bee with Nosema disease. Note that the circular constrictions on the ventriculus are not clearly defined.

. Examine the combs beforehand and make sure they contain little or no honey or pollen.

. Stand the combs up so they are heated in their normal upright position (not on their sides).

. Check to see that boxes and combs have space between them that allows for air circulation.

. Never allow the temperature to exceed 120° F. or the wax will melt. Circulate the air in large rooms so no hot spots are created.

Acetic acid fumigation can also be used to decontaminate bee equipment. When giving this treatment stack hive bodies containing combs on a floorboard outdoors or in an open shed. Place a pad of cotton or other absorbent material previously soaked in 1/4 pint of acetic acid (80 percent) on the top bars of the comb in each hive. Block the entrance and cover the stack with a wooden top. Seal any cracks in or between the hive bodies with masking tape. Leave the stack undisturbed for one week. After fumigation, air the combs for about 48 hours before using them again.

Mention of a proprietary product in this publication does not constitute a guarantee or warranty of the product by the U. S. Department of Agriculture and does not imply its approval by the Department to the exclusion of other products that may also be suitable.