Mushrooms (Many genera)-Bacterial Blotch

Cause A bacterium that can be mechanically spread by water, flies, mites, equipment, and workers. The bacteria can survive in debris and on surfaces, tools, and structures. Bacterial blotch disease of Agaricus bisporus and A. bitorquis is caused by Pseudomonas tolaasii. Burkholderia gladioli pv. agarico is associated with Shiitakes while Pseudomonas cepacia is associated with oyster mushroom (Pleurotus spp.).

Symptoms Infected Agaricus spp. have brown lesions on the cap, initially light turning dark brown. Caps may split or appear distorted when severely affected. Shiitake caps will exhibit a sunken center with lesions, gills turn brown, beginning at the center and working outwards, and the stipe (stem) may also bulge, and sometimes be hollow.

Cultural control

  • Treat the casing with heat or formalin to kill any bacterial inoculum.
  • Avoid high relative humidities and surface wetness. Keep mushrooms as dry as practical. Keep temperatures precise to prevent reaching dewpoints.
  • Prevent or control flying insects in production area.
  • Remove diseased mushrooms.
  • Use disinfectants in water.
  • Start new crops in a clean room separated from older crops.

Reference Fletcher, J.T., White, P.F., and Gaze, R.H. Mushrooms: Pest and Disease Control. 1989. Intercept Limited, Andover, Hants, England. 174 pp.