Why Are My Bees Dying?


Dead Honey Bees

A dead beehive is one of the worst things that can happen to a beekeeper, especially when they did everything that they thought possible to take care of this hive and ensure its survival. Unfortunately, even with the best will in the world, entire beehives can be wiped out, particularly over the winter months. If you have been wondering why your bees have been dying, this article discusses a few of the reasons why this can happen.

Mite Infestation Causing Bee Deaths

Perhaps one of the biggest killers of bees is an infestation of mites. In the U.S., there are two prevalent parasitic bee mites, the tracheal mite and the Varroa mite. Although tracheal mites can infect hives and cause entire colony losses, it is the Varroa mite that is far more prevalent in both the U.S. and Europe.

Tracheal mites are microscopic parasites that invade the tracheae (breathing tubes) of the honeybee. These mites reproduce inside the bees’ breathing tubes and feed on their host’s blood. Mites typically infect bees that are just emerging and affect their ability to breathe. The bees become sick and will typically have a reduced lifespan. This can eventually lead to the demise of the entire colony.

Varroa destructor (Adult Male)
Varroa destructor – Photo by Pavel Klimov

When it comes to tracheal mites, fortunately most bee stocks in North America are resistant to them. This means that infestation rarely results in the death of an entire colony and treatments are not usually required. Beekeepers need to be aware that tracheal mites are not visible to the naked eye and the only way to detect their presence is to dissect a bee and examine the tissue under a microscope offering at least four hundred times magnification. Nevertheless, as most bees have developed a resistance to tracheal mites, beekeepers in the U.S. rarely need to check for their presence.

Varroa mites on the other hand, can be devastating for a colony of bees. Unlike tracheal mites, Varroa mites do not require a microscope to see and are visible to the naked eye. These mites resemble ticks and are about 1.5mm in diameter. They are a coppery red color and feed on the exterior of the bee.

Female Varroa mites reproduce inside the brood cells of a hive. They feed on the pupa and then lay eggs at a rate of one per day. It is not uncommon for hives infested with Varroa mites to appear healthy and to continue producing good crops of honey. However, large colonies of bees that are infested with Varroa mites often die off during the winter months.

If infestation rates are low, there will be very few noticeable symptoms, but as the mite population grows, beekeepers will begin to notice issues with their bees. These issues can include:

  • chewed down brood
  • deformed wings
  • crippled or crawling bees
  • lower rate of return of foraging bees
  • reduced lifespan
  • impaired flight performance.

An infestation of Varroa mites will cause weakened bees and will reduce the number of new bees emerging from cells. If left uncontrolled, a Varroa mite infestation can, as mentioned above, cause the death of an entire colony.

New beekeepers need to be aware that Varroa mites are present in almost every beehive in the U.S., so regular monitoring is vital to keep levels at an acceptable rate. It is recommended that monitoring take place at least four times a year, but preferably at least once per month. Varroa mite levels will be higher at certain times of the year, due in most part to the presence of sealed brood.

It is obviously best to keep mite threshold levels as low as possible. If you have more than one mite per one hundred bees in the spring but more than three mites per hundred bees in the fall, there is a substantial risk for colony loss. Monitoring your mite levels regularly will allow you to treat as early as possible to prevent the death of your bees.

Dead Bees on Ground
Dead Bees on Ground- Photo: flickr.com/photos/youngandwithit

Extreme Temperatures Can Cause Bee Deaths

Mites are not the only cause of dead bees. Extreme temperatures can also result in the loss of a hive, particularly over winter where temperatures can drop quite a bit. This is more common in newer colonies that have not had time to establish large populations.

With fewer numbers, bee colonies are unable to generate the internal hive heat required to survive if temperatures plumet. You can help by placing your hive in a sheltered area, as it is wind chill that causes the most harm to beehives in terms of temperature. Many beekeepers buy a beehive cover or wrap to protect the hive from the elements. Amazon sells a great collection here if you are interested. The link opens in a new tab.

It’s not just cold though, and heat can also be a problem for bees. As such, it is imperative that you ensure your hive is never placed in direct midday sun during the warmer summer months. If the temperature gets too hot, the brood can die. Production will stop as the bees move to the cooler outside and the queen will stop laying.

The optimum internal hive temperature for bees is around 95F. Bees are adept at keeping the temperature optimum if it gets cold or warm, but when external temperatures become extreme, they will struggle and sometimes it can result in the death of the hive.

Bee Fatalities Due to Invaders

During the winter months when food is scarce, it is not uncommon for scavengers to raid hives looking for the nutritious honey within. Bears, raccoons, skunks, wasps, birds, mice, spiders, and beetles have all been known to invade hives or attack bees, particularly in late fall or during the winter months when other sources of food are scarce.

There are things that can be done to prevent your hive from becoming the target of predators. These include fencing the hive in, keeping the hive high off the ground, using robbing screens, or setting traps around the hive.

Dead Bees Outside Hive
Dead Bees Outside Hive – Photo by flickr.com/photos/hayesvalleyfarm

What Are Dead Bees a Sign of?

On occasions you might find many dead bees in and around the entrance to your hive. In such instances, you would need to determine what caused their death. If your hive has been invaded by animals, birds, or insects, it will be easy enough to discern how your bees died. It is not always so obvious, for example, when something like mites is to blame. Consequently, you will need to look for clues as to why they died. And there are signs that can point you in the direction of what happened.

  • One such pointer could be the absence of the queen. If the queen is missing, it means the hive may have been unable to replace her, so there will not be any new brood and the older bees may simply have died of old age.
  • If the dead bees look strange with deformed or missing wings, then a Varroa infestation is the likely culprit. Upon further inspecting the hive, you are likely to see these mites on the bottom board or on the capped brood.
  • Dead bees that are head-down in the cells may have died over the winter from starvation or extreme cold. This is quite common in new hives from which inexperienced beekeepers have taken too much honey and the colony hasn’t had enough to survive the winter. It could also have been the case that the number of bees in the hive were not high enough to generate the necessary internal heat during a particularly cold spell.
  • Moisture and mold can also be a killer, so check for this issue. If the hive appears damp and you spot mold, this almost certainly led to the death of your hive. It is vital that your hive is well ventilated during the wetter months of the year.

If you are unsure what caused your beehive to die, you could always collect a sample of dead bees and send them away for analysis. The U.S. Department of Agriculture (USDA) also carries out inspections, which help prevent disease outbreaks. If you are worried about disease and believe that it may have been the cause of your hive’s demise, I recommend sending a sample of comb to the USDA for testing. You can find a link here for instructions on how to do this.

Dead Tree Bumble Bee
Dead Tree Bumble Bee – Photo by Orangeaurochs (CC BY 2.0)

What is the Lifespan of a Bee?

When it comes to dead bees, one thing that many individuals do not fully appreciate is the fact that honeybees do not actually live for very long. In fact, worker bees live for just six weeks during the honey production season. Of the three types of adult bee in a hive (the queen, the drones, and the workers), it is the queen (responsible for laying eggs) that lives the longest at between two and three years (although some have been known to live for up to five years). During her lifetime, she will lay thousands of eggs.

The queen lays unfertilized eggs that hatch into drones (male bees). These drones will mate with the queen and will either die after a successful mating flight or will be ejected from the hive at the end of the summer season.

By far, the largest number of bees in a hive are made up of worker bees. The worker bees spend the first few weeks of their lives within the hive working before heading out to forage for food.

Conclusion

As you have concluded from this article, there are a number of reasons why honeybees die. Some will simply die from old age, but when an entire hive dies then there is usually an external cause. If your hive has died over the winter months, you should check for signs of invasion, mite infestation, or disease.

If the cause is not immediately obvious, you might need to send samples away for testing. If disease is suspected, it is imperative that this is checked immediately to prevent it spreading to nearby hives.

Anthony

Anthony is a content creator by profession but beekeeping is one of his great passions.

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