Sudden mass die off of strong hive #635258 - Ask Extension


Sudden mass die off of strong hive #635258

Asked May 13, 2020, 11:37 PM EDT

Hi, I had a mass and sudden die off of bees, and I'm trying to figure out what happened.

I'm a first-year beekeeper in Portland. I installed a 5-frame nuc in a 10-frame deep on April 18th. The nuc came with plenty of honey and the weather was good, so I did not feed the bees. My first inspection was one week later, they seemed to be doing well. Still lots of honey, pollen, nectar, etc.  I saw eggs and brood in all stages.

I waited two weeks for the next inspection (May 10th). In those two weeks, the bees had drawn out about 1 1/2 to 2 full frames of new comb (foundationless). During my inspection there were a lot of bees festooning. I saw many foragers coming back with pollen. I assumed all the comb building meant nectar was coming in in adequate amounts, so during the inspection I was more concerned with brood and looking for the queen. I did not pay attention to the amount of honey/nectar stores in the hive (rookie mistake). I remember seeing at least one corner of one frame with fresh capped honey, but I cannot say whether there was more or less anywhere else because my attention was elsewhere. The hive population seemed high and healthy.

On Wednesday (May 13th), I walked out to check on the hive and there were dead bees everywhere. There were blanketing the ground in front of the hive, and there was a pile of dead bees on the bottom board. I emptied the bottom board and there was appx 6-8 cups of dead bees. The rest of bees near the hive seem slow and lethargic. I did not open the hive because it was too cold. I started feeding syrup.

My theories are either starvation or pesticide poisoning. I wondered if starvation could hit so quickly after they were actively building comb just a few days before. I looked for bees with tongues sticking out, and only found a few. Any thoughts on what happened would be appreciated.

Update: Today (May 15) I just inspected the hive. Bees were very calm. No dead bees headfirst in the cells. Just four or five dead bees on the bottom board. There was about a 1 frame of uncapped nectar (a little hard to estimate because, with the exception of one side of one frame, it was scattered about). But there was no capped honey--the freshly capped honey I saw on Sunday was gone. Just a little bit of pollen. Since I put out a syrup feeder on Wed evening, they have taken about six cups of syrup.

House bees were covering about 7 out of 10 frames. The five frames that came with the original Nuc were pretty full of capped brood. The pattern was uniform. There was about 30 cells of capped drone brood on the foundationless frames that they recently drew out. Other than that, the newly drawn comb was empty. I saw about 5 eggs, but it was really hard to see into the cells with the cloudy skies--so there could have been more. I saw just a bit of uncapped larva. Again, hard to see. I will definitely bring a headlamp with me next time.

My overall impression was that the frames were nearly full of capped brood. The four frames on which they have been drawing new comb have not been used yet except for raising some drones. But there was a pretty drastic drop in foragers compared to before. Its was about 63 degrees and dry outside.

I put an entrance reducer on yesterday morning and plan to keep feeding syrup since we have a week of rainy weather ahead. 

Thanks so much for your time.

Multnomah County Oregon

Expert Response

Thnak you for your inquiry and meticulous details. Establishing colonies in spring need significant feeding (sugar syrup) especially when the weather is a bit erratic (few days of rain and then clear weather). The dead bees that you saw intially might have been a result of both starvation and age. It appears that now you have significant open and capped brood in your colony. Please kep feeding syrup until the weather becomes more consistent. If bees are not taking the syrup that you provide, then that means that they have access to some good nectar source and will not need supplemental feeding. Also, please monitor you varroa mite levels in the next 10 days if you have not done so far. Varroa mites can be lethal to your colony if they are not controlled in a timely manner. Please feel free to e-mail me ( or call (979-739-9347) if you have any further questions.
Good luck.
Ramesh Sagili Replied May 18, 2020, 9:55 AM EDT

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