New beekeepers may be surprised to discover that there are many, many diseases that affect our honey bees. It can be a daunting subject to learn about. Here we will attempt to create a down-to-earth method to diagnose and respond when we see evidence of disease in our colonies. Of greatest importance is learning to be observant when we are inspecting them.
A good inspection starts at the entrance. Not only are some diseases first evident at the entrance, but other causes of colony decline, such as skunk predation or gut issues causing dysentery (bee diarrhea) can be found there. There may normally be a few dead bees on the landing board or on the ground. The most hygienic bees carry their dead and diseased bees far from the entrance, so there may not be very many. A large number of dead or dying bees out front may be an indicator of either a very heavy disease problem or of a colony that isn’t very good at cleaning.
A big pile of dead bees is often indicative of a pesticide kill. Surprisingly, not every colony in an apiary will be affected by a pesticide issue. Sometimes only one colony will be affected, or maybe just the ones facing in the same direction. If you want testing done to confirm a pesticide kill, you will need to collect a sample of dead bees, usually about 100 frozen bees in a Ziploc bag without alcohol. Some labs may request wax or pollen samples, so while in the hive, you should collect these as well. At home, do a computer search for “honey bee pesticide residue testing laboratory [your location].” Contacting your state extension service is a good place to start. The USDA-ARS Bee Lab in Beltsville, Maryland1 does not do pesticide or virus testing, but they do offer free bacterial, fungal, and microsporidian disease and pest diagnosis.
A disease that can often be seen at the entrance of the hive is chalkbrood, caused by the fungus Ascosphaera apis. This disease affects larvae only, not adult bees. Larvae that have died of chalkbrood look like little white mummies, and as the number of spores inside a dead larva increases, the mummy turns gray and then black. Each one contains millions of spores, so their removal is of critical importance, since honey bees tend to carry a corpse through the brood chamber on their way out, spreading the spores. As larvae are first becoming infected, they look chalky white and may appear swollen before they begin shrinking and become fully mummified by the fungus. The beekeeper should remove and discard frames with infected larvae and clean the bottom board where many dead can be found. A good thing to remember while inspecting hives is to look down between frames at the floor, which is easy to forget when we are focusing on inspecting brood in the frames …
