Coast Gardener
Watch for azalea pests this spring
Coast Gardener Newspaper and Web Column - April 6, 2002
Azaleas are one of the South's most recognized landscape plants. While spending Easter with my parents, I took several photographs of the more than eighty azaleas in bloom at their house. Azaleas combined with the blooming dogwoods made for a truly spectacular sight.
Sometimes,
however, azaleas suffer in the hot, humid South. Although in full bloom,
several pests were plaguing many of the azaleas I examined. Azalea lacebugs,
or lacewings, can quickly turn a fine azalea specimen into an unattractive
eyesore in your landscape. The upper surface of the leaves appears gray
and speckled while the lower surface of the leaves become dotted with
a black tar-like substance. Lacewings have piercing mouthparts that suck
the juices from the leaves, which give them a grayish appearance. The
insects feed on the underside of the leaves, so control is often difficult.
With a severe infestation of the bugs, lacewings can be observed occasionally
on the upper surface of the leaves. I have observed the heaviest infestation
of lacewings on azaleas that are planted in open areas in full sun.
I have noticed that azaleas planted underneath trees seem to have fewer lacewing problems. Azaleas are acid-loving shrubs, and oaks and pines help to provide proper soil conditions for them to thrive. Like many insect and disease problems, stressed azaleas are more prone to lacewings becoming a problem. Scout your plants every week or so and look for the insects feeding underneath the leaves. Control is easiest when lacewings are detected early. Acephate is the active ingredient in several insecticides that are readily available for lacewing control. Remember, however, that once the leaves become ugly and discolored, they will not recover. Those leaves are damaged, and the focus should be to stop the problem before the lacewings spread to more leaves or more azaleas.
Azalea
leaf gall is likely affecting Coast azaleas right now, as weather conditions
have been just right for its development. This fungus causes pale green
or whitish galls, or tumor-like growths, to form on the leaves. Leaves
are often curled and deformed. Usually, cool, moist weather favors leaf
gall development. The good news is that it will not kill the azalea,
but will make it very unsightly when it is severe. Handpick and destroy
affected leaves. Again, scout your azaleas once a week to look for signs
of this disease. Azaleas are most susceptible to this disease when young
leaves appear. If the galls are not removed from the plant, chances are
that it will be worse next year. It is important to destroy the affected
leaves and not discard them underneath the shrub itself. As long as new
growth appears, azaleas are susceptible to leaf gall. Sometimes it may
not be practical to pinch off all the affected leaves. For instance,
how would you like to manually remove leaf galls on 80 azaleas? What
a job! In this situation, a fungicide is needed. A fungicide containing
bayleton or captan will clear up the problem if sprayed every 10-14 days
beginning immediately after bloom and continuing until new growth ends.
Here in extreme southern Mississippi, we rarely consider winter injury to be much of a problem except for maybe tropical plants. Azaleas, however, often suffer from split bark as a result of cold damage. You know the routine. A period of rain and thunderstorms is followed by a cold front that sends temperatures tumbling in a matter of hours. The temperature slips below the freezing mark causing the moisture in azalea branches to freeze and burst the bark. As a result, damaged branches will turn brown and die during the growing season. Careful inspection will reveal split bark on the branches near the base of limbs or at ground level. Of course, pruning out the damaged or dead limbs is advisable. The best defense against this problem is to ensure the overall health of azaleas through proper fertilization and watering practices. Be sure to water during late summer and early fall to limit the amount of stress on the plants as they enter into the winter season.
Finally, remember to prune your azaleas immediately after they bloom. They need this season's growth to bloom again next year. Azaleas can be pruned to any desired size and shape.
Take time to enjoy this spring's azalea flower show. You certainly will be glad you did.
These archived gardening columns were written by Chance McDavid, former Harrison County Extension Agent.