Hibiscus (Hibiscus rosa-sinensis) is a large evergreen shrub, densely foliated with 6-inch long, glossy-green leaves and 6-inch wide, showy, bell-shaped flowers of white, red, yellow or orange. Hibiscus is native to tropical Asia and grows in warm climates in the U.S. as a border, hedge or small specimen tree if pruned properly. Grow hibiscus in full sun to partial shade on slightly acidic, nutrient-rich soil. Problems of hibiscus include insects such as mites, thrips, nematodes (worm-like soil organisms), scale and a few diseases.
Canker is a fungal disease of hibiscus. Symptoms of canker include branches and twigs dying back. Look for reddish-orange fruiting bodies on diseased bark. Hibiscus death is possible in extreme cases. Control hibiscus canker by pruning and destroying all diseased wood. Healthy trees are better equipped to withstand fungal infection than trees under stress. Minimize trunk and bark injuries that allow fungal pathogens easy access for colonization.
Mushroom Root Rot
Sudden wilting and death indicates mushroom root rot. Hibicus planted in poorly drained soils and in the vicinity of dead and dying plants are susceptible to mushroom root rot. Remove dead and decaying plants, including as much of the root system as possible. Replace or sterilize the soil before replanting. Soil sterilization is achieved by moistening the soil and covering the area with a plastic tarp for about 6 weeks during hot weather. The heat from the sun kills many fungi, insects and weeds.
Leaf spots are usually caused by pathenogenic fungi and vary in size, from as small as a tiny pin-head to spots that take over the entire leaf. Dead leaf areas appear brown, black, tan or reddish and may have a red or purple border. According to University of Florida extension literature, leaf spot in hibiscus is rarely serious. Control hibiscus leaf spot by raking up and destroying infected leaves. Water hibiscus early in the day to allow surface water and avoid overhead irrigation. Excess moisture on leaves for extended periods encourages infection by fungal pathogens.