Soft rot is a bacterial disease. The bacteria identified with this disease are Janthinobacterium agaricidamnosum sp and Burkholderia gladioli pv Agaricicola. Infected mushrooms first display a few light patches which rapidly spread. Within 48 hours the mushroom is a slimy mass. This problem can occur in the growing room but also post-harvest.
It is very difficult to trace the source of the infection. Once infection is present on a farm, preventing further spread is a priority. Pickers containers harvesting equipment and machines can all spread the infection on the farm. Insects are also a major infection vector.
Tackling the problem with chemical agents is virtually impossible. Scrupulous hygiene is essential paying particular attention to disinfecting materials that are used more than once (buckets/containers etc).
The climate also influences these bacteria. Higher temperatures and higher RH both encourage bacterial growth. Good evaporation is a key word here RH below 85% and a lower temperature greatly inhibit bacterial growth.
Mark den Ouden, C point