One reason I do not believe "mite bombs" are a substantial problem:

[Solomon]

I just got back in from checking the three hives that occupy my back porch. Two looked quite good, one dead. Pictures of the dead one attached. This hive was a swarm I caught in an oak tree, about 15 feet off the ground, on the east side of Griffin Creek Road.

This hive consists of one deep on the bottom with two mediums above. The deep is largely empty. The mediums are mostly full of capped honey. The remainders of the diminutive cluster were found in the bottom of the lower medium, shown in the picture (though stacked out of order).

In the picture of the bottom of the deep with three frames removed, you can see a goodly number of mites. This hive appears to have died from a mite pressure resulting in a small cluster. Dead sealed brood was observed, the brood nest occupying about the size of a soccer ball, just below where the cluster remains were found.

This hive was housed on small cell comb, and to my recollection, most if not all of the comb in this hive was provided, not built.

Now, why I don't think mite bombs are a problem. This hive is still full of honey. There is no substantial evidence of robbing. The mites afflicting the hive died with it. Few if any were spread to nearby hives. And speaking of nearby hives, the other two hives on the back porch are in excellent shape, with plenty of stores, and properly sized and located clusters. One was a swarm caught in place (swarm trap), the other was a swarm caught west of North Medford High School in a swarm trap attached to a fence at about chest level.

This is one piece of evidence toward one of the conclusions I have come to as to why mite bombs are not a notable issue, that mites often kill a hive after flying weather is over, and thus the mites die with the colony, not having spread to another colony, and having extinguished whatever virile traits they may have had. The other healthy hives in the immediate vicinity attest to this.

[Flatwoods Bee Farm]

I agree Solomon. I have really started using the "Mite
Black Hole" as an argument against mite bombs. That was a great episode of the podcast.

[GalliaBees]

All hives fail, whether treated or not. So we are ALL producing "mite bombs" or they are a myth. There are so many feral colonies in my area that if the mite bomb theory were correct, the local commercial guy would not be selling 700 hives a year to California almonds and hives would be dying off right and left.

Chris

[Solomon]

I don't necessarily believe mite bombs don't exist. Hives do die of major mite infestations. But not all of them. And nor do those mite infestations always or even usually result in a domino mite crash effect in the surrounding hives. Some hives are so resistant to mites that no bomb could kill them. Others are so unresistant, that no treatment could stop them dying. And all along the spectrum. Many mite bombs happen beyond the possibility of robbing (like this one), some hives don't rob, and many other options. Mite bombs simply aren't that big of a deal, and people should stop freaking out about them, quit treating, let unresistant stock die, and move forward. If we all can do it, others can do it too. Don't blame other hives dying of mites because your hives died of mites. It was because they could not handle the load. That's it. Other hives are doing just fine.

[thom188]

well said

[Michael Bush]

Colonies dying from Varroa in my climate die in the cold when no one is robbing their hives, so the mite bomb "model" simply does not work in any cold climate. Maybe in California.

For argument's sake let's assume there is such a thing as a "mite bomb", lets look at actual numbers. The treatment group includes the commercial people who happened to respond to the BIP survey in 2017. They represent 446,115 hives that are treated. They usually move from place to place and seldom do any swarm control. Those would have probably cast about half a million swarms of bees that probably cannot survive without treatments (being treated bees) which will crash. Of the ones they kept and treated a quarter of those died for a total of 600,000 treated colonies and their cast swarms dying from Varroa. That of course is based on only the responders to the survey. The number is likely much higher. I would guess that the commercial beekeepers are less likely to respond to surveys so these numbers are likely much higher... but that is not provable. We do know that the losses are at a minimum 114,000 by the survey results ignoring the cast swarms.

The BIP numbers for treatment free hives were a reported 35,018 hives at a loss of 45.2% which would be 15,828 treatment free hives that died from Varroa. I would guess that hobbyists and sideliners are more likely to respond to surveys, but that's not provable either. If the numbers are skewed, though, these are likely over, not under represented meaning the spread is likely greater than this. You are not identifying the real problem when you point at treatment free beekeepers. The real problem of crashing hives is the commercial beekeepers.

Assuming crashing hives are mite bombs:
Treatment: 600,000 mite bombs
No Treatment: 15,000 mite bombs

Ignoring cast swarms, for the sake of a conservative argument:
Treatment: 114,000 mite bombs
No Treatment: 15,000 mite bombs

Treaters are definitely causing at least ten times the mite bombs than non treaters and more likely they are creating 40 times as many.

[Solomon]

I've lost a goodly number of hives this fall (I think related to the smoke, but hard to tell, maybe poison). Only one has evidence of substantial mite issues, the one I posted above.

More often what I've seen is colonies that dwindled in size until they could not cluster. What about those hives? They don't get robbed here. Most of the boxes (now sitting on my front porch) still have honey in them. Never robbed. And there is plenty of opportunity, there is a commercial beekeeper nearby.

Mike, you post some interesting numbers. Of course taking the worst case scenario, or the best case scenario from the POV of the commercial, they're way out stripping us in mite bombs. However, in my experience, very few of my hives seem to die of mite crashes. This one was the first one I've found in a couple years, and as mentioned above, this isn't one of mine, it was a swarm I captured, a very large swarm with dark bees, undoubtedly sourced from a kept hive. So given your numbers and my experience, I'd estimate 1000 mite bombs coming from TF hives, established ones anyway.

[Neill Sayers]

I have always wondered if the "mite bomb" scenario isn't simply the normal exponential increase of mite numbers at the end of the season, when broodrearing ceases and the mites are all phoretic.

[Michael Bush]

I agree. I think it’s just the mites no longer have anywhere to hide.

[tommyboy]

just asking...say you have had good success for a couple of years with some treatment free stock,and you introduce a captured swarm into your yard...you don't know what you have ,they may build up well and produced well,then they crash and die in the winter...all well and good ,good riddance to poorly acclimated stock...but here is the rub..it produced a very good brood of drones that have been mating with your new queens,in this scenario am i not doing more harm by capturing a swarm than just leaving it...tommyboy

[Solomon]

just asking...say you have had good success for a couple of years with some treatment free stock,and you introduce a captured swarm into your yard...you don't know what you have ,they may build up well and produced well,then they crash and die in the winter...all well and good ,good riddance to poorly acclimated stock...but here is the rub..it produced a very good brood of drones that have been mating with your new queens,in this scenario am i not doing more harm by capturing a swarm than just leaving it...tommyboy

I would say it's all part of the process. Part of the natural selection is the queen mating with the most fit drones.

The most fit drones are coming from your existing colonies, especially if they are small and fly fast and have good sperm.

Also, a new swarm is going to focus on building for winter and raise relatively few drones the first year.

All accounted for, the process still works. I don't think this is a hiccup at all. We need to think at the higher level, on the species level, rather than the hive level.

[tommyboy]

thank you

[Michael Bush]

>just asking...say you have had good success for a couple of years with some treatment free stock,and you introduce a captured swarm into your yard...you don't know what you have ,they may build up well and produced well,then they crash and die in the winter...all well and good ,good riddance to poorly acclimated stock...but here is the rub..it produced a very good brood of drones that have been mating with your new queens,in this scenario am i not doing more harm by capturing a swarm than just leaving it...tommyboy

There are things you can control and things you can't. One of the issues with people who treat is that they keep watering down the genetics we need. THEY are the problem. People who are not treating are not the problem. But yes, you catch a swarm and they may be contributing drones. But what can you do? The neighbors who are buying packages are the bigger issue.

[tommyboy]

thank you

[tommyboy]

here they are the ultimate mite bomb hives ever

[atollerson]

Tom Seeley did a study recently using mutated blonde bees to see what the true drift and infection rate was between his hives. He established that while there is drift, the hives that succumbed to mite pressure did not have a sudden "large" influx of blonde bees as if they "bombed" outward to send mite infested bees to his other hives. Rather instead, he had 2 small hives that decided to rob out a large hive succumbing to mites, and then those small hives in turn succumbed to mites. The other hives in his apiary remained unaffected by all this drama as they were not out robbing the failing hives. Makes you wonder about the foraging ability of the hives. Suddenly part of the bee genetic equation in natural selection comes down to their tendency to rob out a dying hive? Neat thought.
Regardless, Tom did not see evidence that thousands of mite carrying bees exploded out to find new homes in other apiaries like the term bomb suggested. Rather, it's a slow dying out and reduced population that makes them easily robbed and the mites jump to the healthy incoming robbers. This dynamic is actually favorable to the TF community, in that you could appease your neighbors by claiming to have robber guards on. If you truly did have a hive dying from mite pressure, both your other bees and their bees would be nearly immune with a robber guard. That is if you have any interest in appeasing your neighbor.

[Solomon]

That's an interesting concept. Matches what I've seen. And sets up another paradox, a regulation effect between robbing tendency and mite resistance. That's one of those many traits we talk about that we don't know yet. Seems one of them is "we just don't go collecting mites by robbing out other hives."