Each year I fight worms on my large Woodwardia fern. I've used Safer caterpillar killer with mixed results. Even in a diluted form it burns the fern and is less than effective Any suggestions for prevention?
Neem oil can help in this case. There are many other things that you can do, though. This collection of articles will give you more information on insect control, as well as many other organic gardening tips: https://www.gardeningknowhow.com/special/organic/