Northern Lights Azalea Problems

Chlorosis

• Yellowing foliage, or chlorosis, on a “Northern Lights” azalea is caused by a variety of environmental factors. Soil that is too alkaline -- above 5.5 pH -- causes chlorosis. Add ferrous iron sulfate or sulfur to lower the pH of soil. Because azaleas need good drainage, wet soggy soil also causes chlorosis. Add sand to clay soils to improve drainage or plant azaleas in raised beds to avoid “wet feet." Iron chlorosis of azaleas causes the leaves to turn yellow between the veins while the veins remain green. It is a sign of lack of available iron in the soil. Spray the foliage with an iron sulfate or chelated iron solution, or add iron sulfate to the soil around the roots of the affected plant.

Diseases

• “Northern Lights” azaleas are susceptible to root and crown rots when planted in wet, poorly drained locations or planted with the crown below soil level. Curled or drooping leaves, discolored wood at the soil level and black mushy roots are symptoms of these rots. Fungicides are not effective on root or crown rots. Tiny irregular discolored spots on the blooms are the first signs of petal blight. As the spots get larger, the petals begin to rot. To help prevent the spread of petal blight, remove the infected blooms from the plants and the surrounding area. Treat severe infections with a fungicide labeled for petal blight on azaleas and apply according to the manufacturer’s directions.

Insects

• Azalea lace bugs are small dark-colored insects with lacy wings that suck the sap from the underside of the foliage of “Northern Lights” azaleas. The leaves appear speckled and drop prematurely. Treat lace bugs with an insecticidal soap or insecticide. Adult scale insects look like flat white or brown patches attached to the stems of infected plants. Immature scale insects move around before they begin sucking the sap from stems. Remove scale insects by scraping them off or spray with dormant oil. Insecticides are not effective on adult scale insects. Spider mites are minute pests that suck the sap from foliage, which turns pale green. Treat spider mites with an insecticidal soap. Use an insecticidal soap or insecticide approved for the insect you want to control and approved for azaleas.

Other Problems

• Since azaleas have shallow root systems, the roots can be easily damaged by cultivation or drought. Avoid working around azaleas with hoes, weeders or other gardening implements. Spread a 3- to 4-inch layer of mulch around azaleas to hold moisture in the soil, but keep the mulch from touching the trunk of the shrub to avoid rot. Splitting of the stem bark is caused by rapid temperature changes and freezing. The damage may not be evident for one or two years after the stem splits. Remove the affected limb as soon as you notice the damage.