For protecting your mushroom beds from critters we recommend the following:
- Fencing in your garden
- Agriculture fabric or shade cloth; using shade cloth can both offer your beds protection from the sun and from some insects and animals
- Insect traps; for flies and slugs you can use cups of beer or any other nontoxic homemade traps that you prefer
- Food-grade diatomaceous earth; while this may work for a period of time, you may need to reapply often depending on your environment