Hibiscus is an ornamental shrub that grows to heights of 8 feet and spreads to a width of 4 feet. This showy shrub produces an abundance of 4-inch blooms in shades of pink, red, yellow, violet and blue. Its extended blooming time lasts from July to September, adding a splash of color to any landscape.
Hibiscus is affected by a host of chewing or sucking insects that damage or destroy stems and leaves and may eventually kill the entire plant.
Phytoflora, a soilborne pathogen, causes root rot and crown rot in herbaceous and woody plants and shrubs, causing them to wilt and die when warm weather approaches. Leaves may turn yellow or reddish-purple. The crown may show signs of darkening and may ooze dark sap.
Root rot is caused by the Fusarium oxysporum and Verticillium fungi that breed in the soil and interfere with the plant's ability to uptake water and nutrients. Although roots do not rot until advanced stages, leaves on the hibiscus wilt even though there is adequate water supply. Eventually, root rot kills the plant if not treated promptly.
Left spot canker may kill selected branches or may spread to the entire plant. Small reddish-orange fruit may appear along the bark of the stalk and leaves. Individual leaves may exhibit brown spots that eventually kill the leaves.
Collar rot turns the area where the roots join the stem brown and slimy and is often the result of cool damp winters when the plant does not have adequate drainage to prevent the surrounding soil from becoming soggy.
Hibiscus disease may be transmitted from other plants, but is most often a result of improper plant care. A lack of attention to keeping the area free of moldy leaves and other plant debris, overwatering, and overcrowding contribute to the spread of disease and create the perfect environment for insect pests.
Left untreated, infectious diseases and insect pests not only detract from the attractiveness of your hibiscus plant, but may kill the plant entirely.
Prevention of diseases in hibiscus depends on proper plant care. Cleaning any dead or dying plant debris away from the area, providing adequate aeration by trimming overgrown plants and allowing adequate room for growth and avoiding overwatering maintains healthy plants, which reduces susceptibility to disease or insect infestations.
Collar rot responds to painting the infected area with Bordeaux paste and treating the soil with a strong garlic or chamomile tea. Root rot can be treated with a solution of 1 pt. of household bleach to 2 qt. of water. Saturate the soil with the solution to kill fungi. Application of fungicide to the soil at the time of planting reduces the risks of crown rot and root rot, but proper plant maintenance is the key to preventing disease.