We had a bumper crop of currants last year but virtually all of the fruit shriveled up before ripening. When we researched during the winter for possible culprits, one of the suggestions was to pick the fruit and drop it into
water to see if any worms come out. We had to wait until this year to do so and we did indeed find several worms, as shown in the photo. I think our best bet is to harvest all the fruit we can and destroy it violently, possibly utilizing fire.
As always, I'm looking for advice from people smarter than me.