Problems with your azaleas can be extremely frustrating and disheartening. The blooms you waited for all year are only around for a short while, and any disfigured or unattractive flowers are a big disappointment. Fortunately, the majority of azalea flower problems can be effectively treated if caught early. You may even be able to save the rest of that season's blooms.
The black vine weevil is a small, black, flightless bug. When it feeds on the petals of azalea flowers, it leaves behind notched, jagged edges. Once you notice damage, carefully check the foliage and roots of your azalea and pick off any adult bugs or larva that you find. Then, prevent any more bugs from reaching the plant. Trim any foliage that touches the ground and surround the base of the plant with tanglefoot. Or, consider switching to a species of azalea that is less susceptible to infestation such as Lucky Strike or Jock.
Thrips are another pest that attack azalea flowers. These minuscule bugs find their way inside unopened azalea buds and feed on the petals inside. Afflicted buds either fail to open at all, or reveal discolored petals with pale or dark streaks when they do. Eliminate thrips by spraying your azalea with a narrow-range oil pesticide or by introducing pirate bugs.
Botrytis blight is a quick-spreading and deadly fungus. When the fungus spreads over flowers or buds, they look as if they have been dusted with grey powder. Flowers develop spots and discoloration before they die and fall off the plant. Once you identify botrytis blight, quickly prune and destroy affected flowers, buds or petal litter. Botrytis blight can be killed with a fungicide applied according to the manufacturer's instructions. To discourage it from coming back, keep your plant as dry as possible. Do not wet azalea's foliage when watering its roots, and prune the interior of the plant to improve air circulation.
Flower blight afflicts petals with round brown or yellow spots. Once the fungus spreads, the flowers will wilt and stick to surrounding foliage. Stop flower blight by pruning and destroying affected flowers. Flower blight can be killed with a fungicide applied according to the manufacturer's instructions. To discourage it from coming back, keep your plant as dry as possible. Do not wet azalea's foliage when watering its roots and prune the interior of the plant to improve air circulation.
Powdery mildew, like botrytis blight, covers flowers with what looks like white or light-grey powder. However, powdery mildew is only unattractive, not deadly to azalea's flowers. But it can be a sign that your plant is not getting adequate sunlight or nutrition. Powdery mildew can be killed with a fungicide applied according to the manufacturer's instructions. To discourage it from coming back to attack you flowers, water your azaleas overhead when the sun is at its highest.
Undersized flowers may be a sign that your azalea cannot access nitrogen and iron in the soil. This can be due to any number of problems: poorly drained soil, root diseases or nematodes are the most common. The best course of action is to call a professional to diagnose the problem. Do not simply add more fertilizer to your azalea.