Black Fungus on Abutilon

Soft Scale

• Brown soft scale (Coccus hesperidum) and black scale (Saissetia oleae) insects infest abutilon shrubs. Gardeners often overlook an infestation because adult female scales bear no resemblance to most insects. Their heads and legs are indistinct from elongated, dome-shaped bodies. These scales measure up to one-quarter inch long. A female scale colony on an abutilon branch looks more like a patch of lichen or fungus than a group of insects. The scales pierce abutilon foliage with their mouths and drain the fluids.

Whiteflies

• Bandedwinged (Trialeurodes abutilonea) and silverleaf (Bemisia argentifolii) whiteflies feed on abutilon shrubs’ fluids. They congregate and lay their eggs on the leaves’ lower surfaces, where the legless larvae settle and feed. Large infestations of feeding whitefly nymphs may cause abutilon foliage to yellow and drop prematurely. Silverleaf whiteflies larvae cause silver-streaked, distorted leaves. The tiny, yellowish white-winged adults do less damage than the larvae.

Sooty Mold

• Both soft scales and whiteflies produce a sugary, clear liquid secretion. Known as honeydew, it nourishes airborne mold spores. Capnodium, Scorias and Fumago fungi are most often responsible for sooty mold outbreaks. Their spores land on honeydew-laden leaves and branches, and multiply into a powdery, dark-gray or black coating. Severe sooty mold infestations may completely obscure the shrub's leaves. Sooty mold feeds on the honeydew without infecting the abutilon. A heavy coating of the mold on a significant portion of an abutilon's foliage may limit the plant's photosynthesis enough to decrease its vigor.

Scale Control

• Managing sooty mold begins with eliminating the insects responsible for it. Rain and wind eventually disperse sooty mold after the insects and honeydew are gone. Soft scale control methods include drenching the soil around the abutilon with imidacloprid insecticide. The roots absorb imidacloprid and transport it to the foliage, where it kills scale nymphs. Spraying the shrub with malathion insecticide with applications spaced 10 days apart for six weeks kills overlapping generations of the insects.

Whitefly Control

• Whiteflies are largely insecticide-resistant. Removing an infested abutilon may be the only way to keep the insects and sooty mold from spreading. Vacuuming the plants with a portable vacuum in early morning removing the insects for disposal in a sealed plastic bag is one alternative. Thoroughly saturating both sides of a shrub's foliage with insecticidal soap that coats all the whitefly larvae may also be effective. Apply the soap when the temperature is below 80 degrees Fahrenheit.