The same brown spot can be a bacterium, a mite, or water that sat on the cap too long. Three causes, three different actions, and only one costs nothing.
- By the end you can sort any symptom into three bins: infectious, pest, environmental.
- By the end you can quote the published thresholds behind common button mushroom problems.
- By the end you can order the tests by cost and speed and act on the first cause.