You won't lose the crop. If they're sending up scapes they're on their way out anyway. If you cut off the scapes you'll cut off the moths. Afaik the moths don't affect the roots of alliums, only the foliage. This might be annoying on leeks, but not on garlic.

Thank you, floral! That’s wonderful to know! My instinct last night was to cut off the scapes if they showed damage. How do these larvae work? Enter through a leaf and travel up and out through the scape? I’ve only ever dealt with iris borer that enter the leaf or stem and travel downward and out through the bottom of the rhizome. :p

It seems I was wrong about them not affecting roots. I've read around a bit and what I believed about thrm turns out to be incorrect. But if you cut off the scapes or leaves where you see the damage you should be able to halt their progress.

Sigh. All these years I thought that garlic was always free from pests and disease. Thanks, floral. I’ll keep a close watch. The healthy scapes are almost ready to cut.

Looks like leek moth sign to me too. They are kind of recent to the U.S., you get the joy of being in one of the few states that have them so far. They can keep tunneling down the scape, cause damage to your bulbs, cause rotting issues. Your scapes aren't full out yet and starting to turn but I would remove them now and attend to the damage rather than waiting till you feel they are ready. If you can. Feel down there and see where your heads are at. Cutting the scape too early can lead to smaller heads- they will keep developing, just not as well as waiting for the full turn of the scape. But you are against time with the moths.

Otherwise, treat this like other infestations. When you harvest, destroy the debris. Do not compost it. Remove/clear plant matter or mulch from the bed. When you reset your bed. Keep a row cover over it at night so long at temps are over 45. Leek moths are night wings and are out when temps are over 50, so they can be around to lay eggs or settle in for overwintering in the fall as well as having a fairly early spring emergence. If you can start covering them now, do so. They can have 2-3 generations in a year. You can start disrupting the cycle now.

Garlic has a whole handful of pest and disease issues. It's just a pretty tough plant and seems like it's free.

Thanks for all the info, beesneeds! I’m on it.