I have the exact same issue at my place. We have thousands, tens of thousands of honey bees (not counting a bunch of other pollinators. Certain parts of my yard the hum is intense. Like on my lavender and rosemary. My apples, peaches, apricots, apriums all are loaded with bees. My cherries and plums not as much, pluots and plumcots can be completely ignored. And all of this in my very intensely planted walk and pick orchard where the trees are planted very close to each other. Some days, the bees are busier with the rosemary and lavender, other days, theyāre more busy in my stone fruit area. It is very interesting to see where thy decide to go every day. Clearly, they communicate with each other, and have some sort of group plan with regard to what pollen they want to collect on any given day.
Itās amazing how you guys are struggling with pollination issues with tons of bees. My trees have been pollinated by exactly two bees. I think I know them by name now! The hover flies helped too I guess.
When I first bought my house, I had a swarm descend on my backyard. Back then, I had it taken away by a beekeeper. I wouldnāt have bothered now! 
Well, walked outside to my fruit trees during my morning break, and this morning, I did see a fair number of bees in my cherry trees, along with a fair number of little hover flies/bees visiting about everything. I see some cherry set already in my MR. So, now hoping they donāt abort. Applying triple phosphate today to all my cherry trees. And, I also saw some fruit set on my Flavorella plumcot, which has not set well at all. Not sure if that is due to being a plumcot or the CH. But, looks like Iāll have some fruit this year, which is great.
I had the same issue last year. Was worried about pollination, but outside of the cherries, all was fine. Bigger trees and a lot more flowers this year and itās amazing how many more bees are buzzing.
In my day work, I use an optimization algorithm called āArtificial Bee Colonyā. It tries to mimic the behavior of a bee colony as they search for the most useful food source. Seems to work very well for my optimization problems.
Bizarre. Iāve never encountered that behavior.
Triple phosphate is Ca(H2PO4)2. I know itās easy to broadcast under the trees but I donāt care for it because it adds too Calcium in relation to Phosphate for our soils.
So what phosphate product would you recommend? Remembering that I do not have a fertigation system, so a soil drench is not the most convenient way for me to apply additional phospate. Or, is it potash you recommend to see if I can prevent the fruit abortion I had my my MR and RL last year? I had a fair amount of fruit set for the first time in six years, only to see ALL of the fruit abort at about BB or pea size. Really frustrating.
In my experience thatās a pollination issue. Seen it lots when I cant get a hive under my trees. We have no Phosphate issues in our soil.
I agree and while I donāt know why in my greenhouse the issue is the flowers donāt produce pollen. The female parts are also at times abnormal. I think itās related to the issues weāve discussed recently around flower bud abortion in apricot and pluot. In sweet cherry the flower buds donāt abort but they arenāt properly formed.
So you might check your flowers and see if they look normal. Do the anthers seem plump and full of pollen?
The cause I think is a winter thatās too short to allow full flower development. And maybe lack of chilling. But Iāve gone to 1350 Utah hrs and still had the same issues.
Very interesting Steven. I will take a hard look and report back.
Iād say the anthers look rather anemic. I think they should be bigger and fuller than that. But Iām not sure. Tap your finger tip on the flowers and see if you can pick up any pollen.
Those could just be at the wrong stage to look plump. The stigma and style, female parts, look good.
If theyāre leafed out you could foliar feed them with a water soluble; e.g. a 1/4 teaspoon per gallon of 5-50-17.
Okay, so going to check my flowers (I do think this is an issue with pollination as well, since that has been the running issue all along, and fruit abortionās main cause is pollination issues, from what I have researched), but it cannot hurt to fertilize, and apply a higher P formula. So, will check both. Iām on mainly DG soil, so itās pretty devoid of organic materials, even though I mulch. Thank you all.
The amount of pollen that I could get off by rubbing or tapping was highly dependent on how newly open the flower was. New open ones produced. Older ones not much.
Iām aware that the lifetime of pollen viability varies among Genera but Iāve no idea what it is for true cherries.
My soil is mostly DG in origin, though probably more on the decomposed side. I got home from a 3 day vacation and discovered a great set of cherries on MR and RL, even though I was worried about pollination issues. The fruitlets are about 1/2" in length ā and look to be beyond possibility of abortion. Iād estimate at least 100 cherries on MR and 20 or so on the smaller RL. This is the 2nd leaf in the ground on both trees ā the MR is an older tree on Newroot-1, RL is on Mazzard. I did some hand pollinating earlier this month (though half-heartedly in the dark with a flashlight) ā I believe the pollinators did the majority of the work. I have applied no amendments to my soil, other than some cheap topsoil mixed in at planting. I mulch heavily with a 1ā high mound of mulch around all trees. I really havenāt provided any other care beyond water and a dormant copper spray. So if you canāt get cherries and I canā¦your issue is a mystery to me.
Eric, How new are these flowers? On mine, when the flowers are new the anther tips are yellow and plump. Yours look orange and desiccated ā like those of an older flower. Maybe this is a trick of light from the photo?
Its possible they are older flowers, it kinda hard to keep track of when flowers are opening this bloom because the bloom is so strong. Thousands of flowers on each tree. Ill make note in the coming days and try to catch some super freshly opened ones.
Could it be related to your windows reflecting away too much blue spectrum?