PERFORMING AN AUTOPSY ON A DEAD HIVE
You open your hive after a long winter, excited to see how they weathered the cold. You find hundreds of bees dead in the hive, or none at all.
Finding a hive empty or dead is one of the most devastating moments of beekeeping. The loss of hive, while upsetting, will occur to nearly every beekeeper. It should be seen as an opportunity to learn and adjust your techniques, and should not discourage you from continuing as a beekeeper. There are two classifications of ‘dead hives’. The first is when all bees have absconded – or left – the hive entirely, sometimes leaving behind the queen and a small amount of brood. The second is when a large number of dead bees are found inside the hive. An autopsy of the hive will help determine the reason for the death, and allow you to make changes for the future.
WINTER DEATHS
Most hive deaths that take place over winter are due to excess moisture in the hive, starvation, small or broken cluster, Nosema, or a mice predator.
*Moisture: Like a home, a beehive must have a balance between warmth and ventilation to help the colony survive the winter months. Clusters of bees produce moisture, which needs to escape through the entrances and top of the hive. Improper ventilation can lead to condensation, which will ultimately kill a colony. Mold or water droplets in your hive is a sign that you lost your colony to excess moisture.
*Starvation: Hives can die from not having enough food stores to last the winter, or if the cluster is too small to move toward the food. A cluster found on a frame without any honey likely died of starvation. For more information about feeding bees, visit our article here.
*Broken cluster: On warm days, bees will leave the hive to take cleansing flights. If temperatures drop drastically, the bees are unable to form a cluster and freeze to death.
*Small cluster: A cluster that is too small or lacked adult bees entering winter is unable to keep itself warm enough to survive the cold months. In most cases, these bees die from starvation, as they cannot produce enough energy to both heat the hive and move toward the food stores.
*Nosema: Nosema is caused by a spore-forming fungus that infects the gut of a healthy honeybee, leading to reduced lifespan of the bees and infertility in Queens. Brown or yellow stains inside and outside of your hive is a sign that you have lost your colony to Nosema. For more information on Nosema, please visit our article here.
*Mice: Mice see hives as a cozy place to overwinter. They feed on honeybees, and use shredded comb as bedding. Broken and shredded comb at the bottom of your hive is an indication that mice occupied your hive.
FALL DEATHS
*Robbing: As the winter nears and food becomes scarce, neighboring hives will rob other bees to increase their stores. Symptoms of robbing include ripped honey comb and cappings at the bottom of the hive. To prevent robbing, reduce your entrance during periods of dearth, keep an eye out for aggressive fighting in front of your hives, and place a robbing screen on your front entrance.
*Varroa collapse: Colony Collapse Disorder (CCD) was first reported in the United States in 2006. CCD is a phenomena where most bees abscond, leaving behind the queen and unhatched brood. CCD is largely attributed to varroa mites and their accompanying disease. Bees with varroa become ill and leave the hive to prevent transmission of the virus to other bees within the colony. Unfortunately, the mites and associated diseases spread quickly. If not properly measured and treated, the colony will abscond entirely, leaving behind only a few remaining bees. For information on how to measure and treat mites, please visit our article here.
*Failed Queen: An under-performing or dead queen is a leading cause of hive deaths in the late summer and fall timeframe. Symptoms of a failed queen include spotty or no brood, supercedure cells present, and high number of drones.
SUMMER DEATHS
*Pesticides: Honeybees can be exposed to pesticides by foraging on flowers that have been coated with the chemical, or through direct application. Primary indicators that a hive died after pesticide application or contact include: large number of bees dead outside of the hive and dead bees with tongues out. A test run on a sample of honey can further confirm pesticide exposure, as this can be one of the more challenging hive deaths to diagnose. It is advised that beekeepers check with their local and state websites to indicate hive presence, and to be alerted of upcoming sprays.
*Failed queen: See note above, and our article here.
*Starvation: Colonies can death from starvation occurs anytime of the year, not just winter months. Periods of dearth, poor nectar flows, and the presence of smoke as a result of a local fire can cause a colony to go through their existing stores. We have outlined when and how to feed your bees in our article here.
*Foulbrood: American and European foulbrood are highly concerning reasons for hive death. Indicators include a foul smell, slimy larvae when poked with a toothpick, and discolored brood. Beekeepers who suspect foulbrood should contact their state inspector right away to prevent further spread. Note: Any equipment from American Foulbrood cases must be destroyed.
As a beekeeper, you should be prepared for hive deaths. In some cases, hives can die without any apparent cause. Knowing when and how your hive died will help you better understand the nature beekeeping, and will influence your practices for future years.
Wax on hive frames.
Bees can suffer from starvation even with food stores close by.
Image Credit: Diyana Dimitrova
Knowing the time of year that a hive died will help beekeepers perform the autopsy and prevent future hive deaths.
Image Credit: This photo is made available under the
Creative Commons CC0 1.0 Universal Public Domain Dedication.
