Those are aphids. Using Sevin to kill them is like using a sledgehammer to kill a mosquito. Sevin willl kill insect predators, creating more problems in the long run.

You can either hose them off with a jet of water or (more conveniently) spray the kale with insecticidal soap.

Although your pic doesn't indicate it, you may also have cabbage worms on the kale (larvae). Those can be controlled with Bt.

What slimy_okra said except let me add to it. Water or soap or neem oil will take care of them but you have to be diligent. Spray them off with a water nozzle a couple times a day about 3 days apart for a week or 2. Then, soap the next week about 3 days apart for one week and once every 2 weeks thereafter if the water didn't reduce the populations sufficiently.

Funny slimy mentioned cabbage worms -- I don't see any indication either. In fact, I've noticed through the years that(compared to other brassicas) the caterpillars don't attack KALE as much.

And Yes... BT for all my Moth(caterpillar) needs. Good stuff.

Kevin

using a sledgehammer to kill a mosquito

Great simile! Slimy.

Dave