Beetles Boring into Logs

Fine sawdust coming from small holes in logs; whitish powder from ambrosia beetle tunnels or reddish powder from bark beetles.

Likely causes

• Fresh-cut logs left open in spring and early summer
• Logs stored near infested wood

What to do

Cover logs with fine insect mesh while adult beetles are flying, remove heavily infested logs, and inoculate promptly so the shiitake mycelium holds the sapwood.

Easily confused with

• Wild Fungi and Rots on Logs

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 'Long-horned and ambrosia beetles' (MushWorld). Long-horned beetles (Moechotypa diphysis) lay in the bark but avoid areas where shiitake mycelium is growing well, and a sign is wood dust pushed out of small holes; ambrosia beetles (Scolytidae) bore into the sapwood of freshly cut logs and feed on their own fungus, leaving white dust (bark beetles leave reddish dust) and providing entry for pathogens; both are kept out by covering logs with fine insect mesh during the adult flight period.

Last updated: 2026-10-19