Healthy Hive: Fat happy bees making a contented humming sound. Uncapped larvae is plump and glistening white. The capped brood pattern is compact, convex and tan coloured surrounded by pollen and then nectar/honey. There should be a fresh sweet smell or no odor about the hive.
Varroa Mites: Resembling a small tick, Varroa mites are about the size of a pin head and are reddish purple in colour. They tend to infest drone larvae before it is capped but will also invade other brood cells. Within the cells they reproduce at an incredible rate, feed on the developing bees and lay eggs. You may see them in the pupae or atttached to the bodies of adults.
Nosema: Bees may appear weak, trembling, crawling and are unable to fly, or can only fly very short distances. The hive can have spotting, or streaking of the feces on comb, bottom board and/or the outside. You may see the bees wings positioned at various angles from their body or a swollen abdomen.
Tracheal Mites: Another mite that is a problem for bees and can not be seen by the eye. THis pest lives within the bees breathing tubes. Dissection is the true test for tracheal mites but you may notice bees weakened and stumbling or trying to fly and cannot. Difficult to distinguish because these symptoms can also indicate Nosema.
Chalkbrood: A fungal disease that affects the larvae, often during damp conditions in spring. Infected Larvae become "mummified", they turn hardand a chalky white colour. You may see them in their cells or more likley will notice them when the workers start to remove the carcasses and put them out front of the hive.
European Foulbrood: A bacterial disease of the larvae that causes them to die before they are capped. If they are capped they will appear sunken. The larvae will appear twisted and coiled at the bottom of the cells and they may have a sour odor.
American Foulbrood: A very nasty bacterial disease that affects the larvae and pupae. After they are capped the infected larvae die and go from healthy white to dark brown. The cappings are sunken and may appear perforated and wet. There will be a strong foul odor present. You may see dead pupae shrunken into scale with tongues protruding. Test by putting a toothpick or match stick into a cell and mixing it around. When slowly withdrawing it will be stringy and will "rope" out.
Wax Moths: The best defense is a strong, healthy hive able to remove wax moth larvae they find. If your hive has wax moths you may see cocoons attached to the wood and tunnels in the comb with silk trails crossing each other. There may be wax moth excrement (small dark bits) within the silk. Comb being stored for winter is very susceptible because there are no bees present to defend against the moths.