holleymc
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Joined: Sun May 16, 2010 9:45 am
Location: South Central Virginia

Please help....What are these dark spots on lilac leaves?

Hi all! After battling Bacterial Blight on my lilacs, they now have dark spots on them :cry: . I don't know if its mildew or what. The lighter spots on the leaves I think is residue from the Southern AG Copper Fungicide I'm using to help control blight. Could I be mistaken and it powdery mildew? Any help would be most appreciated! My Lilacs are my favorite shrubs but also seem to be the ones that cause me the most grief! LOL! :D I have four shrubs and only one bloomed this year, possibly from cutting back last year due to the blight. I'd love to be able to salvage them, but I really don't know whats wrong with it. I'm not sure what kind these are.... I think it is the Old Fashioned. :oops:
[img]https://i43.tinypic.com/10q9myb.jpg[/img]

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rainbowgardener
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I don't know about the brown spots. The only thing mine gets is powdery mildew which is light and powdery looking. On a well established lilac, the powdery mildew is mainly a cosmetic issue, doesn't really damage the tree.


Re not flowering, a couple thoughts: When did you do the "cutting back"? Lilacs set the buds for this year's flowers during last year's growing season. So if you did much cutting back, especially in late summer or fall, you were cutting off the buds for this year.

Also I see seeds in the picture. Do you deadhead your lilac?

See my thread here on deadheading lilac

https://www.helpfulgardener.com/forum/viewtopic.php?t=24852

Cutting off the spent blooms BEFORE they go to seed, helps stimulate the production of next year's flower buds.
Last edited by rainbowgardener on Sun May 16, 2010 10:56 pm, edited 2 times in total.
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holleymc
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Posts: 2
Joined: Sun May 16, 2010 9:45 am
Location: South Central Virginia

thanks for such a quick reply!!
Also I see seeds in the picture. Do you deadhead your lilac?
I've nerver thought to do that... thanks for suggesting!!

See my thread here on deadheading lilac

https://www.helpfulgardener.com/forum/viewtopic.php?t=24852

Cutting off the spent blooms BEFORE they go to seed, helps stimulate the production of next year's flower buds.
Thanks so much for all the information! I truly appreciate it!!

luis_pr
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Location: Hurst, TX USA Zone 7b/8a

Gosh, you ARE having a rough time with lilacs, holleymc! You should be enjoying their scent instead!

There are hundreds and hundreds of leaf spot infectious agents out there. The spots can be caused by fungus, bacteria (like your Lilac Bacterial Blight), viruses and chemical injury.

Chemical injuries can happen when one uses insecticides or fungicides that a plant is sensitive to. Even if not applied close to the healthy plant, the vapors can still reach far away plants because of the wind. So consider if you have used any insecticides/fungicides recently. I cannot comment on Southern AG Copper Fungicide because it is not sold here but just review the back of the product to make sure that its use does not have warnings.

Observe which leaves are being infected. If the outer leaves are affected the most (leaves in contact with the sun for example) then minimize as much as possible watering of the leaves and water the soil instead. If that is not possible (say because the sprinkler always hits the lilacs when it goes off) then try to water very early in the day only and water when the soil is almost dry.

If it is fungal in nature, observe good sanitation techniques such as: pick up plant debris; replace mulch if the infestation is heavy; water only when the soil feels like it is drying up; dispose of affected leaves in the trash when they fall down; maintain good air flow between plants (do not overcrowd them); etc. Other fungal infestations are oportunistic; they take advantage of existing leaf injuries to infest the shrub.

Viruses usually spread when you prune an infected plant and then prune a healthy plant with the same pruners. Or when a healthy plant suffers an injury. Roses are notorious because their stems run against each other and the thorns break tissue at times. So dip pruner blades in a solution of water and bleach (1 part bleach, 9 parts water) to disinfect pruners if you intend to prune healthy and sick plants.

Because you already have a bacterial infection and now have another problem, I would send leaf samples to an Agriculture Extension Service or university for analysis. Clemson University's Home & Garden Information Center would be my starting point if I lived in SC: https://www.wistv.com/Global/link.asp?L=50611

I would also keep a list of lilacs that resist Bacterial Blight handy. Just in case you get tired of the constant battle and prefer to switch to other varieties of lilacs... https://plantclinic.cornell.edu/FactSheets/LilacBactBlight/lilacbactblight.htm

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