Diseased pear fruitlets: advice?

We have taken on the management of two established unknown variety dwarf rootstock pear trees. The trees look pretty healthy, and blossomed well setting a lot of fruitlets.

So we were very disappointed that the fruitlets are seriously diseased.

Any information on treatment possibilities for next year, gratefully received.

That looks like a fungal disease to me.  

I would suggest a non-toxic fungicide:

https://permies.com/t/93537/toxic-Fungicide#1423936

Do you know how these trees were managed before and if they had the history of the same disease? It's too late to salvage the fruits but you can make sure the trees get good care this year and situation will improve next season.

The concensus is, these are the signs of pear midge.  Unfortunately, we spotted it late in the cycle, at the stage where the insects are dormant in cocoons in the soil.

The advice at this point (avoiding agrochemicals) seems to be:

1) Cultivate the soil to 3 in and the extent of the canopy, to expose the cocoons to weather and predators;

2) Repeat in mid-late winter, when the insects will be pupating;

3) Thickly sheet mulch in late winter, to block the emergence of imagos;

4) Closely monitor the fruitlets, and destroy safely any which are blackened, distorted, soft or swollen.

These steps should all help to reduce the midge population by interrupting the life-cycle.  A thriving local ecology will help increase predators too, of course.

We started step 1 yesterday: I think I need to go back, pull back the loose mulch, and carefully cultivate deeper however. It's a balance to not damage the roots of these grafted dwarf trees.

Image Grafted dwarf pear tree, cultivated underneath then mulched with rough garden compost.

I never hears of midge so I ask google.  He says in the US we call those flies `no see um`??  something similar to a mosquito?  first discovered in 1877.

So sorry to hear that has affected those pear trees, though it sounds like you have a plan.