disease azalea bush's and black eyed susans

Asked May 17, 2017, 2:42 PM EDT

Hi I'll start with the azaleas. I have encore azaleas some in the shade and some in the sun. The last 2 years I maybe got 1 or two flowers. This year seems worse. Before this we had them for many years and they always flowered profusely, even during the summer. The ones in the mostly shade leaves are turning a slight bright yellow with maybe brown or black small spots, but not many. Then they start to turn brown at the edge. Then they get some spots, but not many. Then yellowish and brown. The other azaleas are in the sun. They start out as more green with with black or brown spots. Then you'll see a little bit of brown on the edge until they turn a rust-yellow-orange color with brown at the tip. Some are just only that rust-yellow-orange color. I just found some that are mostly green starting to turn brown or rust and a little dark red. The black eyed susans which are mostly in the sun and some part shade are still green, with with black or brown all over the leaf and I found that was all that color from the top of the leaf going down both sides and spreading. I'm doing native gardening (I'll probably be back with more questions, but I don't want to inundate you now) so the azaleas are one of the few remaining non-native plants. If you can help, I'd greatly appreciate it.

Montgomery County Maryland lacebugs shrub encore azalea with leaf discoloration rudbeckia with leaf spot

9 Responses

First off, when talking about Encore Azaleas, at 6, they are on the edge of hardiness zones in Maryland. Take a look at this link to a map of your county: http://www.plantmaps.com/hardiness-zones-for-montgomery-county-maryland to see where you are.
The issue is likely a combination of factors, including normal leaf drop, winter damage and pests.
While azaleas can have some problems, which we will cover below, the absence of flowers is unusual. We would like to see a couple of photos of the entire plants, and know more about their placement in the landscape. This can be attached right to this reply.

Are you pruning or trimming these shrubs? It's possible you are inadvertantly pruning off flowering shoots.
That said, we do see some signs of what we think is probably lacebug damage on some of the leaves. Look on the underside of the leaf for black fecal dots and maybe even some of the lacy-winged bugs themselves. It is more likely to occur on regular azaleas in full sun.
Take a look at our IPM Azaleas and Rhododendron publication at this link and compare with what you are seeing: https://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG51_IPM_...

For your Rudbeckia, the first photo looks like a leaf spot disease which can be very damaging, and the second looks like it could be cold damage.
More on the leaf spot:
Septoria on rudbeckia: There are a number of diseases that affect the leaves of the popular black-eyed Susans. One common disease is septoria, which causes dark brown leaf spots. Try to avoid wetting the leaves . For a description of common rudbeckia diseases see: http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/rudbeckia-diseases(link is external).
It can be difficult to control, leading to the removal of beds of plants.



cm

Thank you very much for your response. I went out again to check the azaleas and sure enough I saw bugs on them Tiny white ones ones with black lines. My daughter who has a degree in biology got her entomology book to see what they were. The lace bug. There are many more on the ones in the sun than in the shade even if they both haven't bloomed in 2 years. Now the question is, what do I do?

I hope you don't mind me sending you picture of the leaves in my back eyed susans. I checked your page, but it got rather confusing and I'm getting pretty scared. Thanks again!

I do have a quick question about something else my husband keeps pounding on me to ask you. The branches on our Nelly Stevens Hollies are turning black and leaves are dying. We were told it was black ash borer and need to spray it with oil. We were hoping you could tell us what type of people do this type of work.

Thank you again for all your help which has been fantastic. Glad someone just
told us about you.!



Thank you very much for your response. I went out again to check the azaleas and sure enough I saw bugs on them Tiny white ones ones with black lines. My daughter who has a degree in biology got her entomology book to see what they were. The lace bug. There are many more on the ones in the sun than in the shade even if they both haven't bloomed in 2 years. Now the question is, what do I do?

I hope you don't mind me sending you picture of the leaves in my back eyed susans. I checked your page, but it got rather confusing and I'm getting pretty scared. Thanks again!

I do have a quick question about something else my husband keeps pounding on me to ask you. The branches on our Nelly Stevens Hollies are turning black and leaves are dying. We were told it was black ash borer and need to spray it with oil. We were hoping you could tell us what type of people do this type of work.

Thank you again for all your help which has been fantastic. Glad someone just
told us about you.!



Lace bugs will be a persistent problem on azaleas located in full sun. You may want to consider transplanting them to a location that gets part shade. Here is a link to our fact sheet on azalea lace bugs and several options for controlling them:
https://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG95%20La...

The symptoms on your Rudbeckia are consistent with Septoria Leaf Spot. This is caused by the fungus. It overwinters on infected plant residue and spores are produced in late spring, which is when it spreads. The first symptoms are small angular lesions on the lower leaves. Leaf lesions eventually develop on upper leaves. The spores of the fungus are dispersed by splashing water and can cause secondary lesions throughout the growing season.

Begin control by removing and destroying infected plant material from the previous season. Prevent crowding and promote good air circulation to keep leaf surfaces dry by properly spacing plants and removing volunteers and weeds. Avoid overhead watering. It can be difficult to control and sometimes requires removing an entire bed of plants.

The symptom you describe on your Nellie Stevens Holly sounds like it might be sooty mold. These hollies are susceptible to scale insects (Cottony Camellia Taxus Scale) which produce a honeydew secretion and then a black mold grows on the honeydew. The scale tends to accumulate on the undersides of foliage. Here is some information about this scale and how to control it: https://extension.umd.edu/hgic/cottony-camellia-scale-shrubs

CKC

Thank you for all your information. I'll put the sun azaleas somewhere in partial shade (even though the ones we have in the partial shade, mostly shade, have the same problem) and hope they eventually will bloom.

Will be calling a tree service to spray horticultural soap.

*Just one question about my black eyed susans. They are in the front of my border in groupings and in another bed and all are affected. They're pretty close together now through self seeding. Should I take them all out and replace them with new ones or just take some out to reduce the crowding? I read that some people say it's nothing just ugly or it's overcrowded and just take out dome so they won't be crowded. So now I'm confused as to what to do.

Thank you for all your information. I'll put the sun azaleas somewhere in partial shade (even though the ones we have in the partial shade, mostly shade, have the same problem) and hope they eventually will bloom.

Will be calling a tree service to spray horticultural soap.

*Just one question about my black eyed susans. They are in the front of my border in groupings and in another bed and all are affected. They're pretty close together now through self seeding. Should I take them all out and replace them with new ones or just take some out to reduce the crowding? I read that some people say it's nothing just ugly or it's overcrowded and just take out dome so they won't be crowded. So now I'm confused as to what to do.

Unfortunately, this can become a problem that is more than just ugly. For some stands (even ones that have been thinned) there is just so much disease that the plants end up crispy and brown.
It is your decision if they get to a point that they have lost their attractiveness and you want to pull them. (I personally try to save everything, but this is one case where I gave up and got rid of it all).
There may be disease resistant varieties that would do better for you.

cm

Thank you so much. You've helped me
quite a bit. Out go the black eyed susans and I'll look for disease resitant ones to replace them so i won't have to worrry about them. Makes full sense to me!

Thank you so much. You've helped me
quite a bit. Out go the black eyed susans and I'll look for disease resitant ones to replace them so i won't have to worrry about them. Makes full sense to me!