Beeches are deciduous trees in the Fagaceae family of plants. They have long, scaly buds and alternative leaves with toothed margins. Beeches produce nuts held within prickly burs, and the flowers have both male and female sexual organs. There are primarily two species of beech trees in North America --- the American beech and the European beech. They are nearly identical, except European beech trees have dark grey or brown bark and American beeches have a distinctly smooth, light grey bark.
Sulphur fungus, or Laetiporus sulphurens, is one of the most severe types of heart rot, which decay wood from the inside out. Beech, as well as many other species, are susceptible. Its 2 to 12-inch diameter reproductive structures, called conks, are moist, soft, fleshy and orange-yellow to red-yellow. These conks usually only appear in the fall, crop up as individuals or in groups and only emerge after the fungus has already done years of extensive damage. Trees with extensive rot are particularly dangerous, as large limbs can succumb at any time due to their lack of internal strength.
Scorias spongiosa only effects American beech trees, which grow in the Eastern United States and Canada. It is a specific type of sooty mould that produces thin black layers of fungus, fed by the wastes of beech blight aphid colonies. If left untreated, these fungal masses can grow as large as footballs. Sooty mould is not parasitic, but it harms beeches by covering the leaves --- blocking photosynthesis. This slows the tree's growth and harms fruit production.
Beech Bark Disease
Beech bark disease is caused by an opportunistic fungi that invades the tree after insects have provided an opening. The beech scale insect, Cryptococcus fagisuga, lays eggs in the tree. When these eggs hatch and insects become mobile, they insert feeding structures called stylets into the inner bark; these minute punctures provide an opportunity for at least two species of Nectria fungus to invade. After the fungus establishes, it eats through the bark, killing it. Nectria produce two kinds of fruiting bodies, depending on the stage: tiny, red structures or soft, white structures that resemble the insect colonies.
Most of the 100,000 documented fungal species are either beneficial or neutral to plants and animals. One important example of this is mycorrhizae fungi, which grows around plants' root tips, including beech trees. The fungus extends strands out into the soil, which then absorb important nutrients and water for the tree. In turn, the tree gives the mycorrhizae the food it needs: sugars. Many trees, like beeches, are healthier because of the presence of mycorrhizae fungi.