Rhododendrom problem in Towson

Asked April 5, 2017, 7:43 AM EDT

Attaching additional pictures of problem rhododendron Alan Scherr

Baltimore County Maryland shrub rhododendron dieback

1 Response

Answered under previous question.



"Last fall was very dry and that drought stress can predispose rhododendrons to disease. Our plant pathologist sees a small amount of Botrosphaeria.
We suggest (on a dry day) pruning out any dead branches, back to healthy tissue.
Old rhodies normally respond pretty well to a good pruning.

In times of drought, or when we don't get about an inch of rain a week (a tuna can in the vicinity can help monitor), offer the plant a long, slow drink.
Here is more information:
Botryosphaeria Dieback (Botryosphaeria dothidea)
This is the most common disease of rhododendron in the landscape. A typical symptom of this fungal disease is scattered dying branches on an otherwise healthy plant. Leaves on infected stems turn brown, then droop and roll inward. These leaves often lay flat against the stem and will remain attached. The pathogen can infect all ages of stem tissue through wounds, pruning cuts, and leaf scars. Heat, drought stress, and winter injury can increase disease incidence. Cankers on branches can gradually grow through the wood until the stem becomes girdled. Diseased wood is reddish brown in appearance. Discolored wood viewed in longitudinal cross section often forms a wedge that points toward the center of the stem, and the pith may be darker brown than the surrounding wood.
Management: Fungicide treatments are not an effective disease control option. Plants should be grown in partial shade, with mulch and kept well watered during dry periods. All dying branches should be promptly pruned out in dry weather and all discolored wood should be removed. Plants should also be protected from rough treatment during maintenance activities to prevent unnecessary wounds.

We don't think this is related to the problem with your pine, and are also not convinced that your fertilization played a role"

cm.