WHETHER IT IS CALLED oak root fungus, shoestring fungus, or mushroom root rot fungus, Armillaria mellea in soils can be destructive in orchards, vineyards, and home gardens. The fungus attacks over 600 species of plants and though it usually attacks woody plants, it may also attack certain herbaceous plants including dahlia, rhubarb, potato, and strawberry. Armillaria is found throughout the world in temperate and mild-temperate zones, and is considered to be native to California where it attacks root systems of many plants, but especially the native oaks. Such plants, though frequently infected, are not often killed by the fungus unless they receive summer irrigation or the soil level around them is changed. Following either of these conditions, they may die, and Armillaria is frequently a contributing factor. Even more important is the fact that, when infected trees are removed and some or all of the root system is left in the soil, the fungus will move rapidly through the dead root systems thus creating a reservoir from which the fungus can later attack nearby plants, or young orchard trees set out at such sites. Such plants are frequently susceptible and may be killed rapidly.