Honey Bee Loss - What's The Cause?

Updated: 26th May 2020

Picture of a mass of dead honey beesAbove: Mass of dead honey bees - photograph sent in by Teresa Taramasso of Amarillo, Texas.

I sometimes receive emails from people who are alarmed to find a mass of dead honey bees in the yard.  I am asked how this has happened - were the bees poisoned or sick, and why were they out and about in cold weather in the first place?

For example, I was sent some photographs of lots of dead honey bees by Teresa Taramasso of Amarillo, Texas (below). 

Several dead honey bees.
Two dead honey bees on the ground
Mass of dead honey bees.

Below is the situation described by Teresa, who found lots of dead bees in her yard, and I thank her for permission to use her emails and photographs:

“A couple of weeks ago we had a large swarm of bees appear in our back yard, 90% of them were swarming around my asparagus plants. They seemed disoriented, then by the end of the day they disappeared. Today I found out why….they all died.

In looking at a pile of what I thought was just garden dirt I realized that is was bees, hundreds of them.

What would cause this? I have left them where they died just in case someone wants them.

We’d had a storm blow through from the north but nothing out of the ordinary.  The swarm appeared in my yard and from where I have no idea. I live in a housing track that is about 4 years old…… no large trees around that would hold such a group.  If they were living in the ground they could have been disturbed by construction about three blocks up from us.  I was just shocked to see a swarm that didn't seem to have a purpose of settling to a new home.  I don't use sprays so they must have gotten hit from somewhere nearby, just don't know where they could have flown from or how far they came.  Our last freeze was a couple of weeks ago but they appeared just before that I believe (we had a late season snow).  Very sad indeed.   At first I thought the swarm was made up of thousands of gnats which can come out but as I looked closer I realized that it was bees.

So here are some general reasons for loss of honey bees - and why in some cases, you might actually come across the dead specimens in your local environment.

Reasons For Loss Of Honey Bees 

1. Winter clear out

Firstly, beekeepers may see dead honey bees when the colony is having a clear out and the workers are busy removing dead bees from the hive.   

On a day when the temperature has warmed somewhat, the bees might take the opportunity to remove dead individuals from the hive that have accumulated over a period (the bees may have died for natural reasons).  In these scenarios, the bees may be strewn around the hive entrance and immediate area.

The removal of these dead bees is important in order to preserve hygiene, and although it will seem like many, many bees, it should be remembered that a colony of honey bees has thousands of individuals.  

2. Caught out during cleansing flights

In addition to this, honey bees may need to take cleansing flights (which means they need to leave the hive to defecate) - perhaps they are enticed out of the hive by warm sunshine.  Unfortunately however, during the cleansing flight, it's possible for them to be caught out by the weather, resulting in dead honey bees being seen in the local environment. 

3. Starvation

In addition to this, bees can die during winter due to starvation – the inability to get out and forage, inability to access the food stores, or insufficient food stores in the hive.  Where a beekeeper is involved, hopefully he or she will be able to prevent this happening by supplying additional food for the bees. 

4. Diseases, parasites and predators

Diseases, parasites such as Varroa, and other problems can also take their toll on bees resulting in losses - for example, see colony collapse disorder.

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