Consisting of over 200 species, the hibiscus (Hibiscus spp.) plant helps create a lush, tropical ambiance in your own backyard. Depending on the species, hibiscus grows in U.S. Department of Agriculture plant hardiness zones 4 through 11, producing large, stunning blooms in a range of colors. Unfortunately, hibiscus is prone to leaf spots and fungal diseases.
Various fungus strains cause leaf spot diseases in plants and trees, including hibiscus. The symptoms vary depending on the fungus strain, but generally appear as discolored, irregular spots on foliage. In severe infestations, leaves fall off the branches and drop to the ground. Fallen leaves should be removed and destroyed as soon as possible to prevent the fungus from spreading. Leaf spots are generally tolerated with little to no harm unless the hibiscus is unhealthy.
Rots are caused by various fungi, attacking a wide array of plants and trees. Above ground rot symptoms include discolored leaves dropping prematurely, stem dieback and clusters of mushrooms appearing at the base of the plant. Rots are caused by soggy soil with poor drainage. The best defense against rots is to ensure the hibiscus is growing in well-drained soil. If possible, prepare the site properly before planting the hibiscus by removing all roots of previous plants from the area, improving the drainage.
Bacterial blight affects the leaves of hibiscus plants causing distortion, discoloration, leaf dropping and stem dieback. Botrytis blight affects hibiscus flowers, causing discolored or spotted flowers and possible bud rot. It will also result in discolored shoots and leaves that wilt and drop off the stems. Twig dieback and buds not opening is also possible with botrytis blight. Pruning the diseased branches and providing the hibiscus with good airflow helps control both bacterial and botrytis blight. Other preventive measures include pruning the hibiscus in the dry season when the fungus is less prevalent, avoiding over-fertilization and reducing wet foliage by forgoing overhead watering and instead watering at the hibiscus’ base.
Viruses typically don’t cause too much damage to the hibiscus but can slow the plant’s growth and discolor and distort leaves. No treatment or cure is available for hibiscuses infected with viruses, states the University of California. However, providing proper care for the plant will keep it vigorous, healthy and prevent problems such as viruses. When purchasing plants -- such as hibiscuses -- always buy virus-free and certified nursery stock.
Your Planting Articles
- Fine Gardening: Genus Hibiscus
- University of California IPM Online: Hibiscus—Hibiscus spp. Family Malvaceae (Hibiscus Family)
- University of Florida Cooperative Extension Service: Hibiscus Rosa-Sinensis
- University of California IPM Online: Leaf Spot Diseases
- University of California IPM Online: Bacterial Blight—Pseudomonas Syringae
- University of California IPM Online: Botrytis Blight—Botrytis Cinerea
- University of California IPM Online: Armillaria Root Rot (Oak Root Fungus)—Armillaria Mellea
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