Brown Spot(s) on Rhodo.

Hi -- Seeking opinions on what to do, if anything, about brown spots and discoloration on Rhododendron leaves. I found info about brown spots with white in the middle but there is no white spots on these leaves. Well-establishes plants in Zone 6, NJ
http://members.aol.com/twobtold/Garden/1Rhodo_leaf.jpg
Thanks for any insight.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My best guess is a fugal leaf spot called Cercospora. Generally only an aesthetic issue. Make sure to =remove fallen leaves to partly interrupt the transmission cycle. There fungicides that can be used, but these only effective if used as a preventative, and thus must be used every year, The disease is gen worst when humidity is high in the spring, and when temps. hover near 50 deg F during these humid times.
Good luck
--
Mike LaMana, MS
Heartwood Consulting Services, LLC
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks for reply. Looks similiar if not the same.
http://www.ppath.cas.psu.edu/EXTENSION/PLANT_DISEASE/imgs/050.jpg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
OK, I know that Rhodo also gets Septoria. Maybe a better candidate.
--
Mike LaMana, MS
Heartwood Consulting Services, LLC
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@aol.company.net (Twobtold) wrote in message

Did you have a wet spring last year? It's last years damage. Fungal leaf spot of some sort. Not cured only prevented. In a wet spring you would be spraying fungicides until the cows came home.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@aol.company.net (Twobtold) wrote:

1) Wind and cold damage is indicated when the edges of the leaves become distorted and turn brown. This occurs frequently in plants that may be in a colder climate than recommended or in a location with severe exposure. Note, boron poisoning will create the same symptoms.
2) Large leaved rhododendron are susceptible to sunscald if the plants do not receive enough moisture before the soil freezes. The leaves curl in cold winter weather, exposing the central part of the leaf but not the edges, resulting in the area near the main vein becomes desiccated and turns brown. To prevent this, water plants thoroughly before the first hard frost, protect from drying winds, apply mulch, and locate in partial shade.
3) If a leaf has brown areas with white spots, it probably has a local fungal infection of Pestalotia leaf spot. This is seldom controlled with fungicides and is best mitigated by good sanitation and avoiding excessive moisture.
--
Pardon my spam deterrent; send email to snipped-for-privacy@earthlink.net
Visit my Rhododendron and Azalea web pages at:
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.