Pretty sure BT will cure the cabbage worms and is sound. I've found hand picking is effective for some pests (it can be challenging though). Some Integrated Pest Management (IPM) is a good route, but you need to provide tons of habitat from local flora and don't bother ordering them...just provide habitat and thinks like Brachonid wasps, lady beetles, etc will move in typically. Whatever is local is a plus up.
Although my gardening phase has wound down a lot due to some lifestyle changes...my approach was mainly this: 1) Create the healthiest soil and conditions. Healthy plants are far less prone to infestation, there is even research going into evaluating chemicals that plants give off when stressed which might be linked to predation by insects. 2) Good sowing timing. If your plants grow under optimal conditions they are much less prone to environmental stresses and will outcompete weeds and will recover from damage more readily. 3) Grow well adapted varieties. Ask a local extension or experiment (same reasoning). I recall seeing cabbage moths flocking to my Collards but shying away from my Russian Red Kale completely. 4) Grow things that aren't usually affected. Any Allium is typically really great to grow, almost zero pest issues and usually then those problems stem from improper conditions. These also are more care-free so you have more time to invest in those things you "just have to grow" but might be a challenge in your locale. Mustards are another great choice. 5) Diversify, diversify, diversify. This way if one thing fails miserably due to one reason or another, you have an alternative crop that usually makes it through well. 6) Plant trap crops. I noticed that Japanese Beetles (a problem where I live) tend to flock to the highest point. So a sacrificial hop bine that grows much taller than your pole beans seems to draw them. Or a trap of pole beans when your main bean crop is runner. 7) Learn to ignore minor damage on leafy greens in particular. Unless it's terribly obvious, most of the time the preparation will obscure those little flea beetle holes anyway.
That was my typical methodology, hope that helps!
