Armillaria sinapinaArmillaria sinapina is a species of mushroom in the family Physalacriaceae.DescriptionThe brownish cap is wide and the white, fibrous stem is up to long. Both the flesh and spore print are whitish. The mycelium is bioluminescent.Similar speciesArmillaria gallica and A. calvescens grow only on dead wood but may require microscopy to distinguish. A. gemina and A. ostoyae are also simiilar.HabitatA plant pathogenic fungus, it causes Armillaria root disease, and has been found on a variety of tree hosts in Alaska.