It's important to identify the pest before you treat it, since different pests respond best to different remedies. Also, you want to be sure the insect you're seeing is actually a pest, not an innocent bystander or even beneficial insect. In your case, I can't be sure what the pests are but they might be aphids. In this case, my first defense would be to simply hose off the plant, washing the insects off the top and undersides of the leaves, focusing especially on the new growth. Do this in the morning so the foliage dries quickly in the sun. Try doing this every morning for a few days. If that doesn't control the outbreak, try spraying with insecticidal soap.