Phytophthera?

Asked August 27, 2017, 8:56 PM EDT

four years ago we lost numerous azaleas due to phytophthera. The plants were destroyed. The soil where the affected plants had been was removed and replaced with new well draining soil. Other plants were raised. And new azaleas were planted. A local company drenched the soil with antifungal. The new plants thrived. This spring the same company recommended the soil be tested. No phytophthora was discovered, but recommendation to augment the soil (fertilize) was made. this was done by the company. The plants were not watered since we considered rainfall the spring more than adequate. Several weeks later, leaves on several of the plants began to brown along the edges. The plants rapidly began to die (leaves turning completely brown or just falling off). New soil testing indicated phytophthora to be the culprit as per telephone and treatment recommendation. Two antifungal soil drenches with Adorn, Mefenoxam and Reliant to suppress Phythoophthora are recommended. Does this sound plausible? I wonder if the true culprit was over fertilization this spring? I hate to use so many antifungal products and wonder about their effectiveness. Should I rather exchange the soil in the entire beds prior to replanting. Any advise would be greatly appreciated. Thank you,

Montgomery County Maryland azaleas shrubs phytophthera azaleas with phytophthera azaleas suddenly dying

3 Responses

We're uncertain how long the azaleas have been in the soil. We don't think this is phytophthora. Please read through our page on phytophthora: http://extension.umd.edu/hgic/phytophthora-root-rot-trees-and-shrubs

As you've read above, phytophthora is actually a rare problem, but the pathogen is in the soil generally. Were the plants themselves ever tested for the disease?
Is the site very wet or irrigated regularly?

Alternatively, It could be an establishment problem. We recommend you have a soil test done. Also, read some of the links at the bottom of this page: http://extension.umd.edu/hgic/trees-and-shrubs/common-plant-and-pest-problems-trees-and-shrubs

You are welcome to send us photos of the site, and close-up and near distance photos of the plant for our plant pathologist to see.

ECN


Thank you for your quick response. The plants that died and are dying are of various ages. One rhododendron was about 5 years old and in great bloom this spring. One was 3 years old Several of the azaleas were transplanted in the spring of 2016 from our own yard, 2 others were new plants from Rare Find Nursery. 3 were listed as more resistant to phytophthora. 2 of these are still alive but are showing sign of disease. All of the plants looked healthy in early spring and were in beautiful bloom. I have numerous photos on my iphone but do not know how to get them to you, as well as the results of a soil analysis made in April 2017 prior to Batlett Tree Expert's fertilization. Bartlett is also the company that indicated no presence of phytophthora in April but in its latest sampling done this August concludes that phytophthora is the cause of current disease. Please help my plants. thank you.The whole problem started about 10 years ago, when I had huge azalea plants in the front of the house. One particular plant near a downspout began showing signs of disease and gradually portions of the plant began to die off. This passed on to the neighboring plant and the problem progressed. Of the original plants on the left front of the house only a portion of one of the large plant is left. At that time I did have a soaker hose attached and most likely have over watered. Those hoses have been removed and over the past 4 years I have done no additional watering, except the recommended watering for the newly planted one that arrived in gallon containers.

We suspect that the problems you've had are largely due to transplant shock and failure of the plants to establish well. Rhododendrons are very shallow rooted and won't tolerate being planted too deeply, for example. Very often new plants that were grown in containers are root-bound and the roots do not strike out well into the surrounding soil, resulting in poor water/nutrient uptake. This is a common problem in rhododendrons failing to establish. Also, they need to be in well-drained soil and then watered right at the base of the plant. If your landscaping company has confirmed phytophthora in their test of the soil, you can speak with them about the lab test results and what they would recommend for protection of the remaining plants. Fungicide applications will provide some protection to the plants-- they suppress the symptoms caused by phytophthora, but they will not "cure" it. Phytophtora stays in the soil and it becomes a problem if an area stays very wet all the time (such as where a downspout drains out).

ckc