Fungal Soil Drench for Azalea Beds
Azaleas are flowering shrubs in the Rhododendron genus. They are popular residential landscape ornamentals, not only for their profusion of flowers but because they are so easy to care for. If not cared for properly, they are susceptible to certain fungal diseases. Some of the symptoms of these diseases are attributable to other causes as well, so it's a good idea to get a firm diagnosis of which pathogen is infecting the plant prior to determining how to treat it. Many of the common azalea fungal diseases are controlled or prevented with systemic fungicide soil drenches. Does this Spark an idea?
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Azalea Disease
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Anthracnose outbreaks are common during periods of hot, wet weather. The Cylindrocladium fungus causes root rot in azaleas. Rhizoctonia also causes root rot but it also responsible for crown rot. Rust, caused by Pucciniastrum vaccinii, may result in defoliation of the azalea. There are other fungal diseases that infect azaleas, depending upon region.
Symptoms
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Cylindrocladium-caused root rot has several symptoms, including wilting, leaves that turn brown or black and defoliation. If you notice webbing on the foliage, it may actually be the web-like appearance of the rhizoctonia fungus. Circular yellow spots on the foliage are an indication that the azalea is infected with rust. Any type of powdery substance on the leaves or stems is generally a sign of fungal infection.
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Soil Drenches
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Fungicides are generally sold as foliar spray, which is appropriate for rhizoctinia, another fungal disease of azalea, or as a soil drench. Look for fungicides that are labeled as systemic to ensure you are purchasing a soil drench. Active ingredients include Myclobutanil, PCNB, Tebuconazole and Thiophanate methyl. Some formulas come ready to pour on the soil, others require mixing with water first. Ensure that the soil is completely drenched when you apply the product to the azalea bed, unless otherwise instructed on the label.
Prevention
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Not all fungal pathogens require moisture to germinate but many do. To prevent problems, water the azalea at the soil and not overhead. If you live in an area with frequent rainfall, use a preventive foliar spray between soil drenches. Remove all vegetation that may be crowding the azalea to provide better air circulation. Some fungus overwinter in garden debris, so rake it all up, bag it and dispose of it.
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References
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