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Aug 2, 2010 01:14 PM

Powdery mildew on tomatoes

Not a happy camper this tomato season. We planted three different types of tomatoes in pots, build a wire cage around them to avoid the 'critters' than have enjoyed the crop in previous years, fed them, watered them, DO have several fruit on each plant, BUT........... powdery mildew is running wild, starting at the bottom of the plant that get the most shade. We sprayed with a fungicide (under duress), but the mildew is still moving from the first and second plants affected to the third. The only new flowering is at the very top of the plants where the mildew hasn't reached.

It's been cooler than normal here this summer (Southern California near the beach) and the spot where the plants are gets only 4-6 hours of sun on a sunny day (which have been few and far between). Is there anything else I can do?

Next question..... what varieties can I plan this late in the season here, assuming these will not fruit again due to the mildew?

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  1. Google is always your friend.

    About starting new plants in August, you are kind of out of luck for this year. The earliest plants take at least 50 something days to come to maturity, and from here, that's about October. You won't get much after that unfortunately due to the colder nights.

    10 Replies
    1. re: Jemon

      Thanks Jemon. I found that same resource after my post and have sprayed with a copper sulfate solution.

      With the way summer is coming so late here this year we could have warm weather through November, so if I replace these plants soon, it might be worth a try. My space really limits me to 3 plants, and the one with the worst damage has maybe 15 tomatoes on it now. Last year I planted a Stupice (I think) in August and got fruit in late October........ then it began to fruit again in early Spring before dying. Interesting stuff.

      1. re: Midlife

        You used copper sulphate? It's pretty toxic stuff. I wouldn't eat any tomatoes that got sprayed with it. Any blooms that you have will also probably fall off.

        1. re: Shazam

          Re-checked and I guess I misunderstood what the gardening supply guy said. The product is Lilly Miller Kop-R-Spray and it contains "8% Metallic Copper from Copper Ammonium Complex". How toxic is that stuff?

          A little Googling shows it's used on several fruit crops and the FDA has exempted it from a tolerance requirement because it's "safe":

            1. re: Shazam

              H-m-m-m-m!!!! Time to e-mail Lilly Miller I think. I'm no expert but there seem to be both OK and not OK things in there............. at least at first glance.

              1. re: Midlife

                I would return the product. It's useless for your needs.

                PM cannot survive wet (note: I said wet, not humid). You can simply spray your leaves with water and that clears up lots of PM cases.

                Also, your plants need more sun. They are susceptible because they don't get enough light.

                1. re: Shazam

                  I get it. You're probably right but the product itself saw it does work on powdery mildew...................not that I'd be surprised if water worked just as well.

                  The nursery said that people in this area are having an unusual amount of mildew issues with tomatoes because of the late onset of summer here. It is still about 15 degrees cooler than normal. You ARE right that the place we have for the tomatoes is not in the best light, but this is the 4th year we've grown them and the 1st with mildew problems. Frustrating.

                  1. re: Midlife

                    It's meant for seedlings and transplants. You may cause damage with it on older plants. I've never seen a copper spray that doesn't kill blossoms dead, so I wouldn't use this, especially since there's very effective alternatives that are proven to be safe.

                    1. re: Shazam

                      Lily Miller's garden 'expert' ex-mailed me back saying that while the MSDS does sound scary the tomatoes are OK to eat. Since I've already used the spray I'm stuck with whatever happens. I'd used a different fungicide previously called Spectracide Imunox, which contains microbutinil and 2-butoxyethanol, but that didn't stop the advancing mildew. BTW, the Miller product info doesn't say anything about blossom damage or use on seedlings and transplants only. #!@*!!

                      What would you suggest instead? My trusted garden shop of 25 years unfortunately closed earlier this year so I'm stuck with #2s for advice. It's probably too late for these plants though.


    2. I've used Neem Oil on my peppers and tomato plants this year to deal with powdery mildew. Two applications over a two week period worked, although you can still see the damage on the leaves. Neem Oil is a fairly benign substance as far as its effect on human beings.

      1 Reply
      1. re: raytamsgv

        The Lily Miller garden people e-mailed me that tomatoes sprayed with Kop-R-Spray are safe to eat. That's nice to know, but it does look as though the tomatoes I had growing when I sprayed are all I'm going to get. There are no more flowers or fruit buds to be seen. The one plant we added 30 days after the others has only a few tomatoes on it...... so the bloom-stopping impact does appear to be true. Thanks Lowe's garden guy!!!!!!!!!!! Argh!!! Next time I'm driving the 10 miles to a garden shop that knows what they're doing.