Black Spot and Mildew on peonies

I have problems every year with black spot on my peonies, and last year some got a lot of powdery mildew on them. I was told by someone at a local nursery that Neem oil will work for preventing these things, but you have to get it on the plants before it occurs. Is there anything else I can do to prevent these things organically? I have used chemicals in the past, but have come to realize how harmful to the environment these things are, and I have switched to organic methods. Any help on this would be appreciated. The black spot and mildew don't seem to harm the plants at all, but it's very unsightly.

Karen

Karen, I would say no overhead watering where you get the leaves wet for one. Also, maybe you need to move them so they get more sun? Just a few things I think might help.

Jeanette

Jeanette, thanks for the help. I don't do any overhead watering really. Very rarely. Also, the ones that get the problem are in full sun pretty much all day.

Karen

I'm sure it's from all the rain we've gotten... my Phlox have the black spots too..

Interesting: I found this on the net... wonder if it works...

Both a spray made of a 50/50 mix of fat free milk and water sprayed every 5 days and 1 teaspoon of baking soda with a few drops of a light oil mixed in 1 quart of water and sprayed every 5 days have controlled black spot for me on some nursery stock I got that had it.

and another:

I use a mixture of 1 tablespoon of white distilled vinegar (the kind from the grocery store) per quart of water sprayed on the foliage. It works pretty well. I think the small amount of acid in the mixture is just enough to keep the ph at a level in which the fungus that causes BS cannot thrive but yet it is small enough an amount so as not to burn the leaves. Hope this helps.

You will have to let us know if it works. And, which you used.

Jeanette

Thanks for the help, LH. I may try the vinegar mix. I have read that vinegar will kill weeds, so I hope it doesn't adversely affect my plants. Maybe it has to be full strength for the weeds. I have yet to try it. The temp has to be 70 or above. Actually, in spite of all the rain (or perhaps because of it), I have seen no mildew on my peonies and only a few spots of blackspot. I get the blackspot bad most every year, though it was only last year that I got a lot of mildew on some peonies, though not all. Last year we had little rain, but a lot of hot, humid days.

Karen

Oh, I was re-reading your info on the vinegar mix, LH, and it didn't say how often to spray. Would it be every 5 days like the milk mixture? I don't have enough time to spray that often. I will do what I can, and I will post my results here.

Karen

I can't speak for its efficacy against black spot and mildew, but in order to be a really effective herbicide you really need to buy stronger vinegar than what you can typically get at the grocery store, or with the grocery store stuff you need to apply it full strength on a sunny day and even then it won't necessarily kill all the weeds. So if you're diluting it a lot as you would be here I doubt it'll hurt your plants.

Thanks for that advice, ecrane3. I will keep that in mind. I didn't think it would kill all the weeds, but I imagine it might work well on young weeds, especially seedlings and annual types, but not bigger perennial types.

Karen

I would say, weekly application at least.. I've got to try it on some phlox... with all this rain, they are covered in black spots (well, some of them).

I have some phlox that look awful. And I have some Asiatic lilies that are just turning brown and dying back. Is that some kind of fungal disease? I managed to keep the lily beetles under control with Spinosad, but now this! *Sigh!* Sometimes you just can't win. At least it's only on a few and not all of them. I have to get out and spray the hybiscus with Spinosad (I use the Monterey Garden Insect Spray), as the sawfly larvae are doing a number on them.

Karen

Boytritiis maybe? You might ask in the lily forum... Mainiac was going to use something on her Lillies. The Japanese Beetles have started on the Hibiscus.

I haven't had any trouble with the Japanese beetles this year so far. I'm crossing my fingers.

Karen