Q: What is wrong with my azaleas?

Q: What is wrong with my azaleas? Some of them have died and others have branches that are in process of dying. With all the rain we have been getting, I have noticed that our property stays wet for at least a day or even longer. Do you have any ideas?

A: Several calls have come in during the last few weeks regarding problems with azaleas. My first inclination is to check out the roots because azaleas succumb to a very common disease caused by a fungus called Phytophthora, Phytophtora cinnamomi. The disease proliferates when weather is wet and warm and soil is highly organic. Symptoms include smaller sized new leaf growth, chlorosis between leaf veins, possibly some purple coloration and defoliation. This chlorosis is often confused with a deficiency of iron or other nutrients. At times light applications of iron and complete fertilizer can improve the green color of leaves but only for a short time. Usually, large plants slowly decline in vigor and die branch by branch over a period of several months to years, but sometimes they can die rapidly. Roots are reddish-brown, brittle and often limited to the upper part of a container or soil. The reddish-brown discoloration advances to the larger roots and eventually to the main stem. The disease is common and severe in areas where run-off water, rain water from roofs, etc. collects around plant roots. Azaleas do not like wet feet.

Phytophthora root rot must be prevented as chemicals are often ineffective in controlling this disease after above-ground symptoms become obvious. The following suggestions may aid in the prevention of root rot:
1. Purchase disease-free plants from a reputable nursery.
2. Plant root rot susceptible plants in well drained areas. If excess water from any source collects in the planting site, avoid planting root rot susceptible plants.
3. Do not set the new plant any deeper than the soil level in the container or the soil line in the nursery.
4. In areas where root rot susceptible plants have died, replant with plants that are not susceptible to root rot. You should consider moving the plants to higher ground where the soil is better drained or replacing them with plants that can tolerate the occasional standing water.


Posted: July 7, 2017

Category: Home Landscapes
Tags: Azalea, Phytophtora Cinnamomi., Shrubs

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