fungus on Endless Summer hydrangea

PattyW16(8)August 16, 2014

I have been fighting fungus on Endless Summer hydrangeas every since they were planted three years ago. They bloom magnificently in the spring, but it is downhill from there. The leaves begin to spot and turn brown. Right now several of them have lost all their leaves. I don't think they are dead, but they certainly are not attractive. I have used several different fungicides according to label. Is there hope? Does anyone else have similar problems. Other hydrangeas don't seem to be affected by the fungus.

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luis_pr(7b/8a Hurst, TX)

You do not say which types of fungus is causing the problem. Pictures might help.

Some fungus like powdery mildew can be taken care of somewhat easily but there are some fungi that reoccur and all you can do is treat the plants or replace them. For example, cercospora reoccurs every year in midsummer to early Fall as the fungicides do not prevent the problem in an already infected plant. At best they reduce the symptoms. Cercospora and rust, another fungus that causes rust/orangey spots under the leaves, both rarely kill the plant.

I have some shrubs that came with the house and they had cercospora. It usually becomes visible by now. But, it has not spread to nearby hydrangeas (yet?) and here are some of the things I do: no overhead watering; water the soil early in the mornings and not the leaves, clean the area under the shrub from plant debris; cut off the dried out leaves and dispose in the trash; replace the mulch with new mulch as spores accumulate there from leaves that fall down. I also use a drip irrigation system. You can also separate the shrubs from other plants to improve airflow since fungi do not like low moisture areas.

Oddly, extended periods of drought in my area have improved the look of the leaves. Ironic, is it not?

Fungicides registered for the control of Cercospora leaf spot should have one of these active icontrol ingredients: azoxystrobin (Heritage; smallest application rate and largest repeat interval); chlorothalonil (Daconil); mancozeb (Dithane; Protect; othrers); myclobutanil (Immunox); thiophanate-methyl (Cleary's 3336).

Recommeneded fungicides for rust should have one of these active control agents: azoxystrobin, kresoxim methyl, mancozeb, myclobutanil, oxycarboxin, propiconazole, triadimefon, trifloxystrobin

Here is a link that might be useful: ACES Diseases of hydrangea

    Bookmark   August 16, 2014 at 2:44PM
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Thanks for your response Louis,

I have done everything you suggested except taking out old mulch and putting in new. I wanted to do that early in the spring but the guy that did my landscaping said that would make it worse, by stirring up the spores. I am pretty sure I have both cecorspora and anthracnose. I have used several of the fungicides you suggested and alternated them to reduce the build up of resistance. I am careful to follow directions and repeat applications as directed. We have had much more rain than normal so watering has not been an issue at all this year. I guess the rain has exacerbated the problem. I just want someone to tell me there is hope for these bushes because they are breathtaking in the spring when they bloom--but ugly as sin right now!
I noticed that the hydrangeas at garden center at Home Depot had spots on the leaves. I wanted to put a sign on them telling people not to buy them!

    Bookmark   August 16, 2014 at 3:41PM
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luis_pr(7b/8a Hurst, TX)

It would be rare to have both infections at the same time and it would signal a problem with too much moisture allowing the fungi to develop. NBy the way, I would suggest taking leaf samples to your Agric Extension Service to help identify what the fungus is so you can apply a fungicide that works on that fungus. By the way, I know how you feel about the HD Experience. I saw some oakleaf hydrangeas locally full of rust. I really wanted some of the varieties that they had but declined to pay full price for them. I know they came like that from the wholesaler because they were not in stock a week before but if I owned the local nursery, I would have told the wholesaler to take them back.

This post was edited by luis_pr on Sat, Aug 16, 14 at 23:35

    Bookmark   August 16, 2014 at 5:57PM
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