Had lots of cracking on some of my pears this summer, due to all the rain we had.

Here, stink bugs are certainly the worst insect pest of pear fruit.

One dent/dimple/hole doesn't mean you have a disaster. It might only indicate that a bug started chewing then quit. Home gardeners cut out minor damage, then enjoy the apple.

In order to diagnose the problem, cut the fruit in half, top to bottom, making certain you go through the middle of the hole.

Then post a picture of the cut surface so that we can talk further.

Still would like to see a picture of the interior via a cut thru the dimple/hole.

The one on the left is my Korean Giant (3.9", 12-13 brix, pretty good mild flavor). The one on the right is from a local PYO orchard, which doesn't do a good job thinning their asian pears.

Mine used not to get hit but as tree grows so does the ability to get attention from pests. Half my fruit was damaged by codling moth and/or stink bugs this year, but I still got more than I really want.

http://extension.usu.edu/boxelder/files/uploads/Fruit Production/Cat Facing Insects.pdf [slideshow]

http://utahpests.usu.edu/ipm/htm/advisories/treefruit/articleID=17836#catfi

It is important to distinguish early versus late cat facing. Early (usually extensive) needs be treated as soon as the pollination ceases (the stamens fall off). I would likely try WP Surround [kaolin clay; the white stuff in toothpaste] first because I don't like pesticides but that is up to you after consulting with the CoExt/MGs.

The complaint of seriously warped fruit on one half could be a separate problem. Incomplete fertilization can result in half fruit (being pollinated) the other half not and one side develops the other side not so much.

http://www.honeybeesuite.com/what-is-incomplete-pollination/incomplete-pear/

Yes, I picked the Korean Giant too soon, on 9/24. Next year I'll time it better, but I had only 1 (very large) fruit on the tree (3rd year). It isn't in full sun (sun from 11-12 to late afternoon during summer), but is located up against a tall (8'+) WSW facing stone retaining wall, which keeps it pretty warm. The seeds were mostly dark, though a few were half pale. Even though I wasn't thrilled with it, it was still pleasant and I was happy, as my wife liked it a lot (it's important to get some buy-in for my excessive hobby...). With a few more points of brix, it could be pretty good, especially given how nicely pristine the fruit and leaves were- much better than any of my apples.

The other tree was a 20th Century (2nd year tree), with 2 fruits. I didn't like it that much (~10 brix is too low), but still picked the 2nd one just one day after the first (9/1), due to demand from the kids who loved it. Shinko and Yoinashi will be in their 2nd leaf next year.

Pic: 20th Century on 8/31 (3.25x2.75", 10-10.7 brix, very juicy and crisp)

You're very correct when you say that various agents may be the cause. That's why we won't be able to offer solid suggestions unless we see a cut fruit.

Asian pear fruit can take it down to 20 F., so you can wait until leaves turn yellow to harvest fruit most seasons if they need it.

It's worth it to prune the trees so they are very open as they mature. The only 20th cents. I tasted here that were really sugar were espaliers against a white, south facing wall near Lakeville CT. KG has a tendency to be sweeter.

Charlie,
for me it was the other way around, last year this tree had the first time two or three pears without any deformity.

From Penn State:
http://extension.psu.edu/plants/tree-fruit/fruit-diseases/pear/stony-pit

But, before giving up on the tree, I'd want to make sure it wasn't something else causing the problem. Maybe bag half a dozen pears (zip locks with the corners cut off) when they are still tiny, after making sure they don't have any small bite marks. That should at least keep most bugs and fungus off it.

Thanks Harvestman- with larger crops, I'll make sure to let most hang longer. As it was, the 20th Century were at least equal in flavor (and much larger than) to the PYO Shinshiki & Houshui we picked a few weeks later and the Korean Giant was clearly better.

Both are in warm spots in the yard, with nearby stones which reflect some light and heat. Maybe I should look into finding white mulch. But, given how many trees I have, I don't think anything can compete with freely delivered wood chips.

We are not very far from each others. My 20th century was ripe around mid Sept. KG starts ripening from end of Sept into the first two weeks of Oct. I sometimes had to pick them at the end of Sept for squirrels are the big enemies.

My 20th century is juicy and mildly sweet. KG is crunchy, juicy and a lot sweeter. Mine could weigh 1lbs or more when I paid more attention to thinning.

This year all my Asian pears got hit hard by PC, and OFM and possible, coddling moth, too. Lots of damaged fruit.

The posts on stony pit are good to know. It's worrisome for those who grow varieties that are susceptible.