Largest Russula emetica Found in Japan

On June 30 2026, researchers uncovered a massive Russula emetica weighing over five kilograms during the annual MycoFest event in Aomori Prefecture, Honshu Island, Japan. The find was reported by local scientists and highlighted among the festival’s displays, marking the largest recorded individual of this species ever documented. Attendees measured its cap diameter and overall mass before photographing it and logging the data into the region’s mycological database.¹

The discovery is significant because of sheer size and due to the typical growth habits of R. emetica. This species usually colonizes decaying wood, forming relatively modest fruiting bodies that rarely exceed a few hundred grams. An >5‑kg specimen suggests unusually favorable environmental conditions—such as abundant moisture, optimal temperature ranges, or reduced competition—that allowed the fungus to accumulate biomass far beyond what is normally observed.¹

Experts note that while the record sets a new benchmark for fungal growth studies, the rarity of such massive specimens underscores how variable fungal development can be across similar habitats and reinforces the need for careful documentation whenever extraordinary finds occur.¹