Hibiscuses are popular plants for the landscape and growing indoors. They come in a wide array of colors and different forms. Just like any other plant, they have their own set of issues. Knowing the symptoms of diseases that can affect your hibiscus will help in curing the plant before it is too late. Many illnesses can be cured with good hygiene and airflow others can be treated with special fungicides and good old-fashioned manual labor.
Botrytis (Botrytis cinerea), commonly called blight, affects the buds of hibiscuses causing them to turn brown and eventually drop off before they have a chance to open. It can affect the foliage of plants as well. Affected areas are commonly covered with gray fuzz. Chemical controls of blight include potassium bicarbonate, copper hydroxide and thiophanate-methyl. Organic controls include adequate airflow, proper watering techniques and hand removal of affected areas or infested plants.
Phytophthora breaks out when the soil is left dry in the warm months and plants are allowed to sit in sodden soils throughout the winter. Avoid this affliction by providing adequate moisture when conditions are dry. Well draining soil in the wintertime is also necessary for preventing this soil-borne disease. Phytophthora commonly goes by the name of root rot.
Black spot is a fungus that often attacks hibiscus plants when they are left in damp conditions. Symptoms include black and brown spots on leaves. The leaves may eventually begin to yellow and fall off. Good air circulation, proper watering techniques and careful disposal of affected plants or plant parts will prevent and control black spot. Copper sulfate is also used to treat black spot.
Pseudomonas cichorii is a fungus that attacks hibiscus and other plants. Symptoms include lesions of dark brown, black and tan discolorations on infected plants. Other symptoms are distorted leaves, cracking and papery areas on affected plant parts. Prevent Pseudomonas cichorii by avoiding overhead watering, providing good air circulation and removing infected areas promptly.
Myrothecium roridum is a soil-borne saprophyte that attacks weakened plants. Symptoms include new growth dying, leaves failing to develop, and necrotic tissue. It is spread by infected plants, insects, seeds, gardening tools as well as on hands and shoes. Myrothecium roridum is controlled by allowing good airflow, keeping plants well fed, healthy and good plant/person hygiene.