My guess: snails or slugs. They aren't always around during the daytime but when the lights go out . . .

Sluggo makes an organic slug bait.

There is also a "Sluggo Plus." It has the slug killer (iron phosphate) plus spinosad which will take out insects that eat it. Still organic.

Good Luck!

Steve

Here is my bok choy with similar looking holes in it.

And here is the culprit.

Green caterpillars!
I hand picked a few baby caterpillars off my bok choi, napa cabbage, Brussels sprouts, and artichoke. Then I sprayed BT. Seems to have helped.

Do cabbage worms (larvae of Pieris rapae, aka Cabbage white butterfly) eat Bok choy? Because mine has the same holes.

terrene- Cabbage worms will eat anything in the cabbage family, including but not limited to: cabbage, brussels sprouts, mustards, broccoli, cauliflower, kohlrabi, kale, collards, and bok choy. I'm not sure about radishes though as I never see any significant damage to their leaves.

Rodney

The one mistake a beginner would do is to mulch a already wet bed during wet season. One should know that mulching is not a "everywhere anytime" thing.

Certainly covering what threatens my garden's bok choy.

I have never quite understood the idea of a "catch crop" unless the grower returns and destroys all of the pests, as well as sacrificing the plants.

Left to themselves, something like flea beetle larva will feast on the host plant roots then mature into mobile adults. I would assume that these adults would be happy to move on from the radish, a real flea beetle favorite, to the other garden plants.

Steve