Diarrhea
(Nosema)

Brown spots and streaks on hive box where bees come out.

Fumadil-B
Providing good ventilation really helps!

A protozoan
living in the bee's gut: Nosema apis

If it is a problem, treat package bees in spring with Fumadil in 1:1 sugar syrup. Treat hives with 2:1 sugar syrup in fall. Nosema can be a problem in winter.

An uneven pattern of brood with lots of empty cells. Some cell cappings may look darkened and sunken. Cells may be partially opened by bees. Larvae die after cell is capped. You might smell something bad.

Terramycin
Destroy badly infected frames with scales of dead larvae by burning or discard in sealed trash bags.

Bacteria
Paenobacillus larvae
(= Bacillus larvae )

Not necessary to treat if there is no problem. Watch for symptoms and treat if needed. Srinkle powdered sugar mixed with Terramycin according to the label instructions (3 treatments, 5 days apart).

No obvious symptoms. Mites that are too small to see are inside the breathing tubes of the bees. In winter, infested bees may crawl out of the hive and die.

Usually none required
Some people use menthol crystals.

A mite
Acarapis woodi

No treatment needed. Most bees are resistant to tracheal mites. If your bees die in the winter, purchase queens from a different supplier.

Dead larvae become white or grey cottony "mummies" inside of cells. Mummies may be seen discarded by bees in front of hive. (cool weather problem)

Usually none required
Feed sugar syrup, add more brood or requeen.

A fungus
Ascosphaera apis

No drug needed. Chalkbrood often clears up when weather improves or after a new queen is introduced to the hive.

Look for Varroa mites in capped cells (especially drone cells) or on adult bees. In bad infestations, you see an uneven pattern of brood with some dead brood. Some bees may have deformed wings. Eventually results in death of the colony, especially early winter kills.

Apistan strips
(fluvalinate)
Checkmite+ strips
(coumaphos)
Apilife VAR tablets
(contains thymol oil)

A mite
Varroa destructor
( = V. jacobsoni )

Check for Varroa spring and summer with sticky boards. Many Varroa mites are now resistant to Apistan! Checkmite is very effective but is more toxic and could harm developing queens. Apilife VAR is less toxic but more labor intensive. This is the one bee disease that must be controlled!

Webbing in comb. Wax moth larvae bore right through bee brood and comb, leaving lines of dead brood and webbing. Can destroy good comb! This is a problem of weak or dead hives and stored comb.

PDB moth crystals (Paradichlorobenzene)
are used in stored equipment only. Not moth balls! Bees usually control moths in colonies. Remove dead colonies.

Greater Wax Moth
Galleria mellonella
is especially attracted to combs containing brood and pollen.

Stack hive bodies or supers and put a piece of newspaper on top. Place 1/3 cup of PDB moth crystals on paper above every fourth box. Renew as crystals evaporate. Or kill moths by putting boxes in freezer.

Viral diseases are also important and increase with Varroa infestations but there is no known effective treatment.
Follow all label instructions.