Plant Health Problems

See Rhododendron for a detailed discussion of problems that may occur and are common to members of this plant family.

Diseases caused by Fungi:

Phytophthora root rot and canker, Phytophthora cactorum.
Symptoms include flagging and dieback of individual branches, which may be killed back to the ground. Reddish-brown cankers may be observed at the base of affected branches.

Growth of the fungus is favored by flooding conditions, so severity of disease may be reduced by improving drainage around the plant and avoiding excessive irrigation. If the infection is limited to one or two branches, progress of the disease may be halted by pruning of affected branches. Control can also be achieved with the use of fungicide treatments applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are fosetyl-Al and metalaxyl. Consult the label for dosage rates and safety precautions.

Insect Problems:

Andromeda lace bug, Stephanitis takeyai.
This lace bug feeds on the Japanese Andromeda, Pieris japonica, and occasionally on Azalea kaempheri but rarely if ever on other broadleaf evergreens, including P. floribunda. Both adults and nymphs suck the sap from the undersides of the leaves, causing a mottling or blanching. The adult lace bug is about 1/8" long. The head covering and markings on the sculptured wings are intensely black. Eggs overwinter in the undersides of the lower leaves. There are three or four generations each year. Among the compounds registered for control of this pest in Connecticut are malathion, insecticidal soap or imidacloprid. When needed, malathion or insecticidal soap can be applied where nymphs are feeding during the last week in May, just after eggs have hatched. Imidacloprid, applied as a soil drench, gives systemic, season-long control of this insect. Consult the label for dosage rates and safety precautions.

Southern red mite, Oligonychus ilicis.
The adult mite is extremely small, red, and has eight legs. Eggs overwinter on the undersides of leaves. There are numerous generations each year, with most activity during the spring and fall. Both adults and immatures feed on leaf sap, causing a mottling or blanching. Among the compounds registered for control of this pest in Connecticut are horticultural oil, insecticidal soap, and the restricted use miticide abamectin. Consult the label for dosage rates and safety precautions.