Spraying a pesticide each evening is not recommended, especially if you are not sure who the culprit is.
We'd suggest closely inspecting leaves, including after dark with a flashlight, to see who is visiting and feeding. Hand pick any you find.
Take a look at this vegetable plant profile page on Kale from our website and click on the highlighted links under "common problems":
The use of a floating row cover ( a gossamer-light fabric which allows in sunlight and water but keeps out pests) is highly useful.
Here is a page on floarting row covers: http://extension.umd.edu/growit/beyond-basics/floating-row-cover