While we like to eat fungus in the form of mushrooms, and we use fungus such as antibiotics to treat our ailments, fungus can be harmful to plants by causing disease. Fungal diseases are often difficult to treat because they spread quickly. In addition, fungal diseases may be difficult to spot if they occur in the interior of the plant. Consequently, untreated fungal diseases are capable of ultimately destroying their host plant.
Saprophytic fungus lives and thrives on dead material. These types of fungi attack the root system of plants. In some cases, saprophytic fungus attacks the wood and bark of trees. Infection occurs quickly and symptoms include stunted growth, thin or yellowing leaves and branches that die back. Diseases caused by saprophytic fungus include armillaria root rot.
Fungus that grows on the leaves of plants causes mildew, a disease characterized by a white or gray powder coating on the leaves. This type of fungus likes warm dry days and cool humid nights. Powdery mildew is a named example of the types of disease caused by this type of fungus.
Water Borne Spores
Diseases like anthacnose are caused by fungal spores that get onto the plants during watering. Symptoms of this disease are dead spots on leaves. The death of the leaves causes the branches to die back. Defoliation of trees is a sign of fungal spore disease. Removal of infected branches and efforts to reduce splashing during watering help to reduce the incidence of these diseases.
Rusts are caused by fungi that form pustules on the underside of leaves. The pustules produce spores, which further infect the plant. Symptoms of rust include spotted, mottled leaves and twisted leaves. The remedy for rusts is to remove the infected leaves and avoid watering from overhead.
Smut is caused by fungus in cool weather. Smut affects the leaves of plants and causes uneven growth with streaks that turn black. When the leaf turns black, the fungal spores are released. Smut attacks grasses and the remedy is water deeply in the morning to help the plants grow. Late and light watering will encourage the fungus to grow.