This is very bad year for grey mold. No, backward… It is good for grey mold, it is bad for me 
! So I lost number of berries to it. But there is something I don’t know how to explain. I mulch my strawberries in spring with shredded leaves I collect in fall from my neighbors, mostly maple and oak. I found that none of the berries that were laying directly on mulch or even buried in the mulch(not sure how it happened) have no gray mold at all. You pull that berry from the mulch, it is covered in some spider web, has leaves pieces stuck to it, but under that - it is just perfect ripe berry. All the mold located on hanging/staying berries/stalks. I know that mulch prevents splashing on berries, but this is irrelevant to my case(both hanging and laying berries are protected), I would expect berries laying in mulch be in worse condition(wet longer) that hanging. Unless the leaves have some anti-fungal properties. I know that oak bark has antibacterial property, but leaves?
I used to mulch with straw, but I suspected it was just breeding botrytis
Great observation, and I will be using leaves, as I have hesitated in the past. Your best preventive is captan, but it must be in acidic water, it will not work at all if not in acidic water. I spray before flowers, or during flowering, 2 sprays eliminated all gray mold. Can be applied up to harvest, so i assume once you start harvesting not to spray? Not sure what that means? My 2 early sprays were enough, late in season a few might get it again. But harvest is light after June.
I was spoiled by three drought years in a row, so didn’t even think of protecting my strawberries before mold appears… .
Please note that leaves has to be finely shredded, whole leaves(especially large ones) make very bad mulch, tried it before…
Yes a good point and I do shred mine with the lawn mower, and sometimes with the leaf blower set to pick up leaves. Mine has a metal impeller that does a good job of shredding, you can run through again for leafs that are somewhat fresh.
I bought shredder/chipper specially for leaves shredding, found it to be a good investment.