Staghorn ferns, members of the Polypodiaceae family, are tropical plants native to Australia, Indonesia, America, Africa, Southeast Asia and the Philippines. There are 18 species of recognised staghorn ferns and a wide variety of hybrids, according to the University of Florida IFAS Extension website. Grown as houseplants in nontropical areas of the United States, staghorn ferns are susceptible to the development of diseases, which can affect the health and appearance of the plant.
An excessive amount of moisture in the soil of staghorn ferns can make them susceptible to the development of Rhizoctonia sp., which is a fungal disease. This disease causes symptoms of root rot and can cause staghorn ferns to become stunted. Other symptoms associated with the development of Rhizoctonia include the development of black spots on the plant, which attack the plant and kill it. Reducing room humidity and withholding water from the plant may help slow the progress of the disease in a houseplant. Chemical controls are generally effective when used on staghorn ferns with Rhizoctonia.
Algal Leaf Spot
Algal leaf spot is a disease that affects a wide range of plant species. Houseplants such as the staghorn fern are at risk of developing leaf spot diseases. The symptoms associated with algal leaf spot include pale green or red leaf spots on plant leaves and rough spots with feathered margins on leaves. Wet weather is favourable for the development and spread of this disease. Remove any infected leaves that appear on your staghorn fern by hand and use good sanitation practices. Chemicals are available for treatment of algal leaf spot.
Powdery mildew is a common disease that is easily recognised by the white, powdery fungus growing on plants. Powdery mildew affects all types of plants, grasses, shrubs and trees. While there are several types of fungi that cause powdery mildew, they all produce similar symptoms. Colorado State University lists the symptoms of powdery mildew as spots of white or grey fungus on plants and small, fruiting bodies developing on upper sides of plant leaves. Infected leaves can become yellow, distorted and drop from the plant early. Flower buds, stems and the bottom of plant leaves are also affected. Powdery mildew is often severe in warm, dry climates. Remove all infected leaves by hand and avoid overhead watering. Spray the staghorn fern with a fungicide in severe cases.