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Southern blight/white mold

Julie717
10 years ago

One of my plants died from what I think was Southern blight aka 'white mold'. It was the second of five plants in a row, it was fine one day then totally wilted the next. Hoping it needed water (though very unlikely considering the other plants were fine), I watered it and when it didn't revive by the next day, yanked it out. I inspected the plant and noticed white cobwebby fibers encircling the main stem at the soil line, which is what I based my diagnosis on.

That was three days ago and the other plants all still look fine. I was wondering if I should expect this to spread to the other plants or if I might have stopped it by pulling the plant. I did not see any of the sclerotia (spores), so maybe I got rid of it early enough? From what I've read of this infection, there isn't much I can do to stop it from spreading to the other plants if it's going to spread, but if anyone here knows something different, I'd like to hear about it. Thanks, everyone.

Comments (5)

  • digdirt2
    10 years ago

    white cobwebby fibers encircling the main stem at the soil line,

    Sounds like damp-off to me. It will take a plant down in 24 hours but SB will not. Not even Late Blight takes a plant down in 24 hours.

    Damp-off can occur at any time when the soil is kept too wet.

    Dave

  • julia42
    10 years ago

    Interesting - I didn't know that about damp-off. I had a plant do something similar this year, after a heavy rain. The plant was a good 2 feet tall and pretty robust at the time, but it just turned totally limp overnight. I pulled it, but never found out what the problem was. Maybe that was it - I always thought dampening off just happened to seedlings...

  • digdirt2
    10 years ago

    Damp-off (aka damping off) is a collective term for a number of different issues caused by different fungi at various stages of plant growth. While it is most common in seedlings it can develop at any stage of growth given the proper conditions.

    Rhizoctonia solani is the usual fungi that causes damping-off of seedlings and cuttings. Also Pythium spp. Phytophthora spp. are usually associated with root rots and damp-off of established plants. There are several other variants as well but the things they have in common is excessive moisture and/or inadequate air circulation in and among the plants as with over-crowded planting.

    Dave

  • mule
    10 years ago

    Julia

    I think you had the correct diagnosis.

    Once you see this disease and how fast it acts, you don't easily forget it. I saw it with some frequency throughout growers fields in the southeast. Even methyl bromide treatments were not that effective of preventing it once it set into a field.

    In the short term it is hard to say whether or not the other plants will get it or not. It can be spotty in a field or eventually take out large areas.

    It's a pretty nasty disease once it sets in an area.

    For the long term it is in the soil and you will likely see it again if you plant in that same spot.

    I listed a site below but recommend googling other edu sources to see if there are other newer recommendations for dealing with it. It is a problem in Florida so I suspect this link will probably be as good as it gets.

    Only a handful of varieties show some resistance to this disease. I doubt that you will be able to find them even if I told you which ones. Most of these lines were developed 50 or more years ago.

    Since methyl bromide has been banned there has been some renewed interest in looking at these older lines and breeding for resistance. If they make headway it still will be years away and likely released in commercial lines.

    I have some of these old lines. I started to make crosses to heirlooms with them over a decade ago. Since I moved more north (and west) I lost interest and the project went on the backburner. I have recently started to work with it again. It's difficult for me because I have no way to test them (and dont want one!). I instead will use a breeding scheme which will increase my chances of retaining the resistance.

    I cannot share seed of the original source lines. My source was through the university they were developed and the USDA (back in the 90's). Last I looked the lines had been pulled from the USDA list. Over a decade ago I did offer seed of these lines but there was little interest. If anyone of those people did keep seed it might be around. I did not keep record of who I sent them too. But I have never seen anyone offer these lines. They are what I would call "standard" field tomatoes (avg tasting, good sized red round balls) so I suspect without knowing or understanding what they really had most would have probably not cared to save them.

    Here is a link that might be useful: Integrated Management of Southern Blight in Vegetable Production

  • Julie717
    Original Author
    10 years ago

    Thanks Dave, I'm not sure about damping off. I don't think I was overwatering because I hadn't watered in more than a week. It had rained about four days before, but only about an inch. That's what made me think it might just be drought stress at first.

    I guess overcrowding is possible, they are only planted about 3 ft apart, however there is only one row. These are mature plants about 4ft tall with lots of tomatoes.

    Thanks Mule, for the info and the link (I am Julie, another poster named Julia responded). It was Monday when I pulled the plant and so far the others look fine but I keep thinking I will come home from work one of these evenings to a row of dead plants. That was the weirdest thing I've ever seen, at least as far as gardening goes;). I sort of expected to find all the roots had been eaten by a critter or something when I pulled it.

    It sounds like all I can do about this year's plants is cross my fingers and hope for the best, in either case. I am considering solarizing the soil in my tomato patch, and I will definitely be planting in a different location next year.

    I will try to remember to update this thread to let you all know how the other plants turn out.

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