By the way, it is not Cladosporium fulvum. The mold is a fuzzy gray, only on the top of the leaf - - nothing on the underside.

Raybo

Looks like the early signs of powdery mildew (Oidium spp. not leveillula taurica). Eventually would be evident on upper and lower leaves and get progressively worse.

You can probably find a sulfur fungicide already pre-mixed. Good that you caught it early. Bleach is toxic to plants. Good luck.

Here is a link that might be useful: Powdery Mildew

I had the same spots last year on a couple plants and it did progress upward. However, the plants that had that same spot mold yeilded fruit just fine through most of the summer. Could be do to lack of air circulation. Just my 2 cents, good luck Raybo.

Damon

Ray, I gave an organic control --if you use Gardeners Disease Control (daconil) I just looked up the label and it mentions mildews.

With sulfur remember not to spray with oils for 3 weeks.

Thanks folks, looks like the Oidium strain since just the top of the leaves is affected. Will check out some natural sprays at the local plant shop. Glad to hear it should not impact the tomato production.

Raybo

Ray, I agree with Farkee as to Oidium type powdery mildew.

It's quite common in CA when the so called June Glooms appear. Prompt treatment with Daconil should get the situation under control. Sulfur would be my second choice b'c it just isn't as effective. And this disease can affect production if there's continual loss of foliage.

Carolyn

"Sulfur would be my second choice b'c it just isn't as effective."

Carolyn, I have never heard this before--do you have a source?

I always see sulfur listed as a primary control on various university sites. I always consider it first when I think of powdery mildew.

Ray, I would not consider sulfur against septoria or early blight so if you are trying to prevent these diseases as well as powdery mildew you could use Daconil (unless you want to say you are growing organically). For the treatment of PM alone sulfur is considered an effective option. Follow label as per temperature restrictions. You would want to use other fungicides for other diseases but it is a good idea to alternate anyway.

Here is a 1998 study by the Univ. of Conn. that evaluated 5 fungicides for controlling PM. Sulfur was considered superior over Daconil (Bravo) (chlorothalonil).

""We recently evaluated the efficacy of five fungicides for control of powdery mildew under field conditions in Windsor, CT. On 2 Jun, 1998, five plants of Celebrity tomato were transplanted per plot to each of 5 replicate field plots in 3 rows 5 ft apart with 2 ft between plants in each plot. Two additional untreated border rows were planted to act as a source of inoculum. Plants were staked and tied but not pruned or suckered. Tomato plots were left unsprayed or treated with either sulfur (Kumulus, 15 lb/A), benomyl (Benlate®, 12 oz/A), chlorothalonil (Bravo®, 1.5 lb/A), copper hydroxide (Kocide®, 2 lb/A), or azoxystrobin (Quadris®, 5.6 fl. oz/A) on 24 Jul, 7 Aug, 20 Aug, and 4 Sep. Plants were evaluated for percent foliage with powdery mildew on 10 Aug, 31 Aug, and 10 Sep. Ripening tomatoes were harvested from plots on 25 Aug, 3 Sep. 10 Sep, and 17 Sep. Data were analyzed by the nonparametric Kruskal-Wallis analysis at P=0.05.

Severe powdery mildew developed in the border plants and spread to the field plots (Table 1). Other foliar diseases, such as Septoria and Alternaria leaf spots, were low in incidence and not seen in the field plots or borders until late in the season. All fungicides evaluated resulted in less powdery mildew than developed in untreated control plots.

Sulfur and Benlate® had superior efficacy early in the season, and Benlate® and Quadris® were superior at the late evaluation.

Bravo®
and Kocide® were intermediate in efficacy. While the trend was for lower yield in unsprayed plots, there were no significant differences in fruit yield as a result of the late season powdery mildew that developed in these experiments.""

Here is another link that discusses the use of sulfur against PM (LT).
http://utahpests.usu.edu/plantdiseases/files/uploads/PestMonitoring/tomato_powdery_mildew.pdf

Ray, I would definately treat this early to try and stop its progression. Advanced cases are very hard to control no matter what you use.

THis would be an opportunity to experiment with Serenade --using it preventatively on some of the plants that don't have it as it doesn't seem to be all that effective controlling existing disease. Sulfur , or whatever you choose on other plants. Then compare the results. Your plants are very close together so you will have to keep on your toes combatting this.

Good luck.

Ray, I did some further checking and premixed sulfur spray I was thinking about (by Saferbrand) doesn't list tomatoes on the label. They list alot of vegetables but not tomatoes.

Whatever you use would have to be labeled for tomatoes so you may have to resort to something else.

Your overall yield wouldn't be effected anyway no matter what you choose as long as you get some measure of control

If you are growing organically besides Serenade other products listing Powdery mildew are Concern fungicide (Neem oil) and Greencure (baking soda).

I did a non scientific experiment once on a friends VERY INFECTED powdery mildew tomatoes. Serenade and home-made baking soda formula weren't effective. Did see an improvement with sulfur but no matter what you use, including Serenade or Daconil, you need to use preventatively or at the very first sign of disease but I know you know that already.

Carolyn, I have never heard this before--do you have a source?

*****

No, no source to link to since I moved to this latest computer and lost almost all my faves, thanks to AOL. Sigh.So I've had to rebuild my faves as I go along. Sometimes I can remember specific site addys, but most of the time I can't.

And for me to go on a search and destroy mission now to find where I was reading about it, and I'd put two links in my faves, is not something I want to do right now.

So, Daconil if Ray wants to use it and Ray, my position is that I could care less if a product is organic or not, b'c what I'm concerned with is toxicity. Daconil can be appled to the day of harvest and has about the same toxicity, which is minimal, as does Rotenone, which is approved by every organic certifying agency I know of.

And there are scads of threads in the back threads here about Daconil so I'm not going to go into that here. Anyone can also go to EXTOXNET, for starters, to check out any product.

Stick with links that have .edu at the end b'c there's a tremendous amount of dicey info posted by those who are fervent organic growers, if you catch my drift.

Ray, do what you feel comfortable doing for your affected plants.

Carolyn

Carolyn,

I also don't care if someone chooses organic or synthetic fungicides. I only suggested sulfur , not because it was an organic control, but because I have seen it recommended as a control for PM over most others.

That was why I was curious why you said sulfur was not as effective against powdery mildew as daconil and why I looked up the Connecticut study.

I just like to have accurate information and that is a new one to me. But don't worry about finding your source--it is not necessary. Daconil controls other diseases as well so Ray may very well choose to use it.

I just like to have accurate information

***

And as you know so do I but in this case I'm simply not going to Google and look at a bunch of links to find what I lost.

Carolyn

Carolyn is a source! I've learned alot from her. I'll be glad to listen when you say something Carolyn.

Carolyn, I know you have said that daconil is superior in its control of early blight when compared to copper but this is the first time I recall you talking about powdery mildew and the efficacy of sulphur. Anyway as I said no need to look up anything.

This is from Ortho Disease Control Label:
Doesn't mention control of PM on tomatoes. And it only has a weak control (ie suppression) for downy mildew on a few other vegetables. I was surprised --as I thought it was a labeled control for PM.

LABEL:
Tomato Early & Late Blight, Gray & Septoria Leaf Spots, Gray Leaf
Mold, Anthracnose, Alternaria Fruit Rot (Black Mold), Rhizoctonia
Fruit Rot & Botrytis Gray Mold

(Even the Bravo label doesn't mention PM.)
But here is an informative brochure from Davis (Calif)
on powdery mildew--maybe it would help make a control decision.

I learned things I didn't know. Never knew fungicides could be considered 'eradicants' as well as 'protectorants'.

According to this brochure hort. oil or neem oil are good eradicants (but don't use oil with sulphur or vice versa --they are incompatible and watch out for high temps).

I really like UCDavis material. (along with Univ. of Fl, of course)

LABEL:
http://www.scottssti.com/en/08_resources/fact_sheet/GardenDiseaseControl06.pdf

Thanks all for contributing your knowledge on the leaf problem. Based on the discussion, I think I will give Neem Oil a try. I really do like to avoid all pest control whenever possible, even if it means a reduction in production.

Thanks,

Raybo

I really like UCDavis material. (along with Univ. of Fl, of course)

****

I do as well Farkee. The link you gave to the UCDavis site is their IPM site so it would be expected that other ant-fungals wouldn't be mentioned other than those that are so called organic.

As for Daconil, I've recommended it for both kinds of Powdery Mildew in the past and the feedback has been positive. I have been less impressed with those who have used Neem, and that from online feedback alone. Neem was going to be the wonder product for all sorts of things when it first came out but those expectations just haven't been met according to the feedback I've seen.

But each situation is different as to location, degree of disease, etc.

The Petoseed lab is considered the best in the world as to tomato diseases and I do pay attention to what they recommend.

For Oidium they say:

"Several fungicides including sulfur can be effective in controlling this disease if good foliage cover is obtained and they are applied in a timely manner."

Source: Tomato Diseases, published by Seminis Seeds, a monograph that I find very useful.

Sulfur is not suggested for the other Powdery Mildew, just other good anti-fungals.

The pictures in this monograph are the same that folks will find at the TAMU site and others b'c they all know the excellence of the work done on Tomato diseases at the Petoseed Plant Pathology lab.

Whatever folks use is up to them after reviewing a particular situation and choosing something to treat with that they're comfortable with, as I said above.

I don't hold stock in Daconil, LOL, but feedback from it has been excellent and it has more data accumulated, worldwide, than any other anti-fungal, and that's good.

Carolyn