Effective fungicides

wexgardenerJune 25, 2014

Have a case of leaf spot on guelder rose and lilac Joly shrubs am wondering what's the best solution this have applied bordeaux mixture to them to stop fungi growth( will it kill the fungi?) should I try lime and sulphur mixture spray or would hydrogen peroxide work? Ive heard that hydrogen peroxide might kill the leaves is it true ?

I've heard baking soda mixed with vegetable might work as well as skimmed milk can any one shed some light on the effectiveness.

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ken_adrian Adrian MI cold Z5

who made the diagnosis ...???

i would have expected complaints of mildew on lilac... long before i ran up to leaf spot ...

and i would never bother to treat PM on lilac.. its cosmetic.. the spray wont remove it.. though kill it ... so you end up using chems or whatever... for what amounts to nothing ...

can we have some pix.. to see what is going on.. before we encourage you further ???

you confused me.. by calling a viburnum.. a rose ...


    Bookmark   June 26, 2014 at 8:15AM
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cecily(7 VA)

Lime/sulfur spray is applied to fruit trees in late winter. Spraying it on anything at this time of year will destroy all foliage.

    Bookmark   June 26, 2014 at 9:43AM
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Here's what on the guelder rose

    Bookmark   June 26, 2014 at 11:23AM
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On the charles joly

    Bookmark   June 26, 2014 at 11:25AM
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Click on the small box in guelder rose post
I was told by a guy in my local garden centre it was leaf spot is there any universal fungicide that kills all fungi on plants

    Bookmark   June 26, 2014 at 11:27AM
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cecily(7 VA)

If you've already applied bordeaux mixture, then you need to just stop. Spraying one fungicide after another is going to burn the foliage. Once spots appear, they will not go away -- fungicide will prevent more spots from developing but the existing spots will remain for the rest of the growing season. if you don't like the appearance of the shrub with spotty leaves, you can pluck off the damaged leaves, water well and wait for new foliage to appear. Good luck.

    Bookmark   June 26, 2014 at 3:21PM
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Actually, neither plant is affected by a fungal problem - they both have a bacterial leaf spot known as 'lilac blight', Pseudomonas syringae. The Bordeaux mix is a recommended treatment for this problem however in a mild, damp climate, adding some sort of surfactant (spreader sticker) to the mixture will give longer lasting effectiveness. And it is important to note that this treatment is not going to be curative - the best it can do is prevent the disease spreading to unaffected foliage.

The good news is this disease on many woody shrubs (like these) is considered more cosmetic than harmful. Make sure you follow good cultural practices by cleaning up all the foliage in the fall and destroying it and perhaps even utilizing a dormant spray to kill any overwintering infection. It is also suggested that liming the soil may limit the development of the problem.

    Bookmark   June 27, 2014 at 2:53PM
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