First, identify the culprit! That takes some prowling around, poking through the foliage, even stalking the kale after dark with a flashlight.

If you are observing holes, the possible culprits are caterpillars, beetles, slugs or snails, pillbugs or earwigs (if your plants are young), and maybe others I'm not thinking of.

It's a bit of a waste of time to think about a plan of attack, unless you know who the enemy is.

Agree with the above. You can't just blanket spray or use anything without doing some harm ranging from killing the beneficials to killing the plant itself.

So first you have to find out exactly what is doing the damage. Then you evaluate how much damage is being done and if the plants are tolerating it or not. THEN you pick the least toxic approach for that specific pest.

"Something is eating my kale" can mean anything from the whole plant is gone to there are a few small holes in some leaves. Specific details, esp. a photo, will not only help ID the problem but determine what, if any, treatment is required.

Dave

First you must find the critter(s).
Then you must dispatch by appropriate means, which includes handpicking.

Kale is in the same plant family as Cabbage so they6 have4 many of the same pests. Aphids, Flea Beetles, Cabbage Loopers and European Cabbage worms, but each has different methods of control.
Aphids can be kept under control often with just a sharp water spray.
Flea Beetles are a little more difficult, but trap crops and Floating Row Covers can help.
Cabbage Loopers and the European Cabbage worm might need applications of Bacillus thuringiensis - Kurstaki while they arte young or something a bit more toxic later.

Here is a link that might be useful: Common vegetable pests