Is it possible that the cold wet May prevented bees from pollinating the blueberry flowers--if bees and insects are the pollinators for blueberries? I know that can happen with other fruits.

Do you have winter moths? My blueberries have been decimated by winter moth caterpillars during the last 2 springs. Haven't seen a berry (or bloom) in two years. :(

Hmm, yes, I do have that horrible infestation of winter moths & tent caterpillars (are they the same animal?) and forest tentworms and gypsy moths (not so many of those). If it was a bad caterpillar, I had them - in my hair every day when I went out to the garden for awhile, falling out of the trees (I can deal with most insects, but NOT in my hair; gross!). I guess that could be the answer. Our weather was weird, too - judging from posts on this forum earlier in the season, that may help control the caterpillar problem this year - let's hope so.

I got enough blueberries to make a batch of muffins, and I left a few out there for my bird friends. Dayenu.

I agree about the winter moths. Blueberry leaves are one of their favorite foods. I spray with BT (non-toxic organic control) when I first see those nasty caterpillars, and that helps quite a bit. Shade is also a big problem for blueberries, mine are now really in too much shade and barely produce, even in a good year. Enough for a batch of muffins sounds about right.

I'm impressed, you guys! We have TONS of them here and even when the crop is "bumper", I can't beat the birds to them.

Kim,

Contrary to most posts above, it's been a good blueberry year here. A break in the wet weather just as they were ready to pollinate, then enough rain to plump them without watering. Have a couple gallon bags in the freezer.

Only cultivated varieties of high-bush, though I've rejuvenated some wild h-bs with success in previous garden.

Thoughts:

 Haven't noted moths that others mention. Do have some tent caterpillars, but not as severe as previous years.

 Freaky weather this year. May have been raining just when yours needed pollination, the bees were hiding? Several organic veg farms nearby keep hives, I reap the fringe benefit.

 Shallow-rooted, they don't tolerate weeds well. (Mulch with capital M). Also, they prefer acidic soil, don't lime.

 Wild? Do you prune? I've had luck with late winter/early spring trim back to healthiest branches, no more than 3 years old. Count from the ground: year 1, a new shoot from roots w/ just leaves. Year 2, branches from axils (last year's leaf nodes). Year 3 sub-branches as above. Year 4, cut that branch back to the ground, forcing growth to newer branches. Fewer berries, but much larger.

 Book-learning says some varieties need a different variety as cross-pollinator. Unlikely to be your problem as you've had good harvest in the past. I include for others who may read this thread.

I, too, found decidedly few wild blueberries overall this season...I looked in fewer areas than usual (usual is a "Lot," sometimes many many places in my overall area, N Central Mass/southern N H.

Ginny, I agree it seems that the wet cold spring during spring seems very possibly the main reason why...I remember watching day after day of rain and cold while the blueberry plants were blossoming, and thinking, oh darn, this could ruin the berry prospects this year.
What an unfortunate thing in a way--with the subsequent plentiful rains that have followed this whole summer, it's seem this could have been a very, very special year for berrying!
One odd thing about this factor and blueberries, at least judging by another recent result--last year's very similar (from what I remember, and where I am at least) weather during blueberry blossoming--is that there'd seem maybe more to it...unless last year the foulness wasn't "quite" as ceaseless, and maybe a couple of warm sunny days saw adequate pollination taking place in a really concentrated way? Lots and lots of blueberries last year, where I am.

Overall, distinctly still pretty mysterious, as well as somewhat fascinating

Cultivated blueberries may be a little different, besides usually I think, being treated to brought-in honeybee hives for pollinating (which
"still" "might"to my unknowing thinking, require some special bee-motivating know-how on the part of the growers in wet spring years, because honeybees more than most other bees even, particularly balk I understand about going out on cold days)...
...and also, cultivated bbs bloom later than wild blueberries.

--Mephisto
(Eric)

Solana - I have enough acid soil, I'm sure - essentially the blueberries are sitting on forest floor - yard is partly wooded.

I don't prune or mulch - everything's "as is" back there; this is the first year I've noticed any drop in production.

Eric, last year was a bumper year for me, too.

Another factor that could have reduced pollenation of wild blueberries this season, is--ironically--the mild low-snow winter just past. It seems that, outside of the presence in the neighborhood of tended domestic honeybee hives, it's just the wild insects of various types, that are left to do pollenizing of things like wild blueberries. But, unfortunately, the stocks of wild insects are less than fully reliable themselves--such as when low-snow winters reduce the insulating protecting depth of snow that helps them survive our cold winters.
To add even more unease to this sense of harm--it'd seem (to me anyway--just by personal estimation from my own observations)that the by-rights fairly high attractiveness of bluebery blossoms to wild insects and wild-types of bees, seems to vary from one season to another. I've seen one of their best wild pollenizers--bumblebees--sometimes passing up blueberry blossoms in favor of other blossoms, when in theory they "should" be going right for the blueberry blossoms. After bearing heavily in years like last year (in some areas), maybe (or to me, more like, "likely"--but I haven't real proof) the wild blueberries' blossoms produce less of the nectar and pollen that leads to the wild insects' favoring of them.
As so often hapens in nature, various natural factors I think seem to exist, favoring one thing (one outcome), disfavoring another, with the net result being I suspect a possibly understandable even predicatable one, if only all the factors were known.

Besides all the plausible explanations provided here, it's also true that productivity can go down on older bushes, especially those with canes more than 4-5 years old. The prescribed remedy is to prune older canes and branches in the fall and let new growth fill in. You may not have a good harvest the following season, but the year after the amount of flowers and berries should increase.

As you've had your blueberry bushes for a while, it may be that they just need to be rejuvenated with pruning.