Why Do Bad Things Happen to Good Azaleas?

Bad, Bad Fungus

Phytophthora cinnamoni Root Rot

Plant foliage appears wilted, even in the early morning. The fungus plugs up the conductive tissue in the roots, preventing mositure from reaching the upper parts of the plant. Not only azaleas, but also dogwoods, pieris, yews, camellias, laurels, junipers, blueberries, and pines can suffer from this fungus. There is no cure; remove all parts of the infected plant, and dispose of them. Do not plant any other susceptible plant in that area until the ground has been sterilized.

Root rot thrives in a wet area because the fungus only becomes infectious in water-saturated soil. The best preventative is to plant only in well-drained soil. If you have wet, heavy clay or upland silt which stays soggy, yet you want to plant azaleas there, build a raised bed.

Ovalinia azalea Petal Blight

Here's a problem which can show up among the late-blooming azaleas. Petal blight fungus can transform azalea flowers into a brown slimy mass if there is warm, wet weather at bloom time. Infected flowers turn brown and fall to the ground, developing spores the next spring.

Toxin-lovers answer: Spray the flower buds just as they begin to show some color with Triadimefon. If the weather stays warm and wet, spray them again when the flowers open.

Toxin-haters answer: Pick off all the brown flowers and dispose of them. Cover the fallen flowers with enough mulch to cover them completely, 1-2 inches.

Return to the top of this page

Bad, Bad Insects

Lacebug (Stephanitis)

Bad News

These are awful little bugs! They came from Asia, where natural predators kept them from sucking all the chlorophyll out of everything. They have become a great problem in the northeast USA, including Howard County. Lacebugs are tiny, fly-like, sucking insects that hide under a leaf and suck out chlorophyll. And they hatch four times a year, so you have to check for them in May, June, July, and August. Ick. Look for whitening of the leaves and lots of icky little bugs underneath.

Toxin-lovers answer: Acephate, applied in May. Good for a year.

Toxin-haters answer: Insecticidal soap, 85% effective, applied every month as a spray. Be sure to get the underneath part of the leaf.

Good News

U.S. Department of Agriculture experts believe that since the natural enemy of the lacebug, Stethoconus japonicus, has now been discovered in the USA, this predator will play a very significant part in reducing the damage done by lacebugs.

Return to the top of this page

Bad, Bad Animals

Rabbits are fond of azaleas, but fortunately rabbits are not very tall and constitute a menace only to young or dwarf azaleas. They tend to nibble off twigs rather than gnawing the bark off major limbs.

Deer, especially hungry deer whose forest clearings and meadows were just replaced with a housing development, can develop an appetite for azaleas too, particularly during dry or bleak winter weather.

Return to the top of this page

Bad, Bad People

Mulches which duplicate the native habitat of azaleas in woodlands help maintain soil temperature and moisture levels. Loose, coarse mulches such as pine needles, wood chips, oak leaves, and shredded bark are ideal. Proper mulching is second only to watering in keeping azaleas healthy and attractive.

Too much mulch, however, can lead to root damage and to death. Anything which is over 3 inches deep or packs down tightly can cut down the oxygen exchange between the roots and the air. The symptoms of over-mulching resemble other root damage: yellow leaves, poor growth, dieback, and death.

"Not only is over-mulching a waste of mulch, but it is rapidly becoming the number one cause of death to azaleas, rhododendrons, dogwood, andromeda, boxwood, mountain laurel, hollies, cherry trees, ash, linden, spruce, etc. Repeated applications of mulch cause suffocation of the roots of shallow rooted species."

From Nurseryman's News Dr. Francis R. Gouin Chairman of the Department of Horticulture University of Maryland

Return to the top of this page