Wild Fungi and Rots on Logs

On shiitake logs: green or yellow patches on the log ends, dark crusts or small hard red-to-black dots on the bark, bark peeling off, or turkey-tail, Stereum or other conks growing on the log with dark lines where they meet the shiitake.

Likely causes

• Logs in direct sun or too dry
• Logs not inoculated soon after cutting
• Too-wet or poorly ventilated log yard

What to do

Shade logs with shade cloth, inoculate soon after felling, keep log moisture around 30–50% with good airflow and drainage, and remove heavily infected logs from the yard so spores do not build up.

Easily confused with

• Green Mold (Trichoderma)

Not sure?

Walk through the troubleshooting guide, ask the AI Grow Consultant, or check the conditions your species needs on its species page.

Sources

• Mushroom Growers' Handbook 2: Shiitake Cultivation (MushWorld, 2005; Spanish edition by CERZOS), chapter 5 'Biology and control of pests and diseases in shiitake log cultivation' (Korea Forest Research Institute) (MushWorld). Wild wood fungi cannot be blocked from outdoor logs; if the environment is well managed they are not a serious problem. Pathogens that kill shiitake mycelium include Hypocrea schweinitzii (Trichoderma longibrachiatum), whose damage follows at least a day of direct sunlight on logs; Hypoxylon, with hard brick-red to black fruiting bodies of 2–10 mm that appear in late summer, in dry, medium-temperature conditions; and Diatrype stigma (Libertella betulina) with orange spore masses and hard crusts under the bark; competitors that only take space and nutrients include Coriolus (turkey tail), Stereum and Inonotus (wet, warm conditions) and bark rots in poorly ventilated, badly drained yards in the rainy season; basic practice: keep log moisture at 30–50%, give ventilation and drainage, avoid direct sun, inoculate on time, and remove infected logs promptly.

Last updated: 2026-10-19