My Azalea Remembrance Tree Is Wilting

Azaleas are also known as rhododendrons.

The azalea "Remembrance" cultivar blooms with bright pink, five-petaled blossoms on deep green foliage. While striking, this cultivar is susceptible to both phytophthora root rot and verticillium wilt. These diseases damage the tree's root system, cutting off its water supply and causing wilting.

Phytophthora Root Rot

This disease is caused by a soil-born fungus that infects and kills roots. Initially infected azaleas suffer from stunted growth and slightly yellowed foliage. They may droop or wilt during the day but recover at night. As the disease progresses, infected plants will wilt permanently and eventually die. Wet, warm soils favor fungal growth and you may see reddish streaks extending from the soil up the lower portions of the stem.

Phytophthora Root Rot Control

Once phytophthora has taken hold of your azalea, there isn't much you can do. Infected plants may linger for years but won't recover. If your azalea starts to wilt but is receiving adequate irrigation, don't increase the amount of water you give it. Keep the soil as dry as possible to slow the spread of the disease. If you are worried about the disease spreading, remove the cultivar and replant with a resistant variety. When you replant, amend the soil with sand to improve drainage and set the new plant high so no more than 1 inch of soil covers the top of the root ball.

Verticillium Wilt

Also caused by a soil dwelling fungus, verticillium wilt enters the roots through injuries caused by insects or other pests. Once inside the roots, spores move through vascular tissue and restrict water flow to all or parts of the plant. According to the University of Minnesota, the disease can be chronic or acute. Chronic symptoms occur yearly and are often worse just after cool weather. The entire plant may be stunted while leaves become discolored and wilt. Wilting can be seen on all or just part of the azalea. Acute symptoms include widespread wilting, curled and discolored leaves, branch dieback and eventual death of the entire plant.

Verticillium Wilt Control

Because the symptoms of verticillium wilt are similar to phytophthora root rot, the University of Minnesota recommends getting your soil tested to confirm which fungus is infecting your azalea. Plants infected with verticillium can survive in the landscape if given adequate water; drought-stressed plants are more susceptible to the fungus. Fertilizers high in potassium and low in nitrogen can also be helpful in extending the life of your azalea. No cure for verticillium wilt exists, but it can survive in the soil for quite some time, so if you do decide to replant, look for resistant cultivars.

References

• Virginia Cooperative Extension; Phytophthora Root Rot of Rhododendron and Azalea; Mary Ann Hansen; May 2009
• University of Minnesota Extension; Verticillium Wilt of Trees and Shrubs; Cynthia L. Ash