Use 'wormy' to evoke a strong visual picture of something being eaten or damaged by worms. That old bookshelf looks so wormy, I bet it's been in the basement for decades.
Pro Tip 2/3
Negative Connotation
'Wormy' suggests poor conditions or quality, often provoking disgust or aversion. I wouldn't sit on that wormy couch; it looks like it's about to fall apart.
Pro Tip 3/3
Literal Use
'Wormy' can be used literally, to describe something that actually contains worms. You can tell this corn is really wormy just by looking at the holes in the husks.