Late Blight on Tomatoes

kbarbJune 27, 2005

[ I have this posted in the Pests and Diseases Forum (=Garden Clinic) but someone in the Tomato Forum pointed out this forum, which I didn't know about, so I'm reposting it here. ]

In our community garden here in San Francisco we have a small incidence of Late Blight on a few tomato plants, due to the late June rains and cool weather.

I have removed the blighted leaves and stems, but I'm wondering about the 3-4" black areas on the main stems.

1. Should I pull the whole plant - or will it spread to the rest of the plant or other plants ?

2. Is there any treatment for this? I'm curious what the normal methods would be, although we have an organic garden so my options are more limited.

I gather from other replies that it splashes up from the soil, although I think the spores are probably also carried in the wind.

Anyway, it seems that the plants are doomed if infected and living in cool and moist whether.

But if the weather drys and warms. . . ?

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carolyn137(z4/5 NY)

but someone in the Tomato Forum pointed out this forum, which I didn't know about, so I'm reposting it here. ]

I'm that someone. LOL

Barb,

Do you have any pictures and/or are you absolutely convinced that what your plants have is Late BLight ( P.infestans)?

I ask only b'c Late BLight is not common in your area, as you know, Late Blight is lethal, regardless of the weather, and from the time the typical symptoms first appear the plants will be a mass of black stinking tissue within 1-2 weeks.

What might be sprayed would be sprayed as a preventative, not after the fact, and products available to home growers are not very effective, to be quite honest.

No, it doesn't splash up form the soil unless infected plants had been grown there in a previous season; all new infections are airborne.

Has someone made a definitive diagnosis for your plants re Late Blight?

If not, do you want to go thru some descriptions on your part and questions on my part?

Carolyn

    Bookmark   June 28, 2005 at 8:58AM
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kbarb

137,
I don't have pictures of our own infestations, but they look exactly like

Thanks,
Barb
(Kent)

    Bookmark   June 28, 2005 at 12:54PM
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carolyn137(z4/5 NY)

137, ( please call me Carolyn, thanks)

I don't have pictures of our own infestations, but they look exactly like this

OK, if the plants die it's P. infestans, if they continue to live please consider Gray Mold which can be confused with Late Blight in early stages and thrives in the same cool wet conditions that Late BLight does.

The only anti-fungal that seems to have some protective effect, that is available to home gardeners, is Daconil, aka chlorothalonil, aka Ortho Garden Disease Control.

I don't know of any organic products that have been shown to be effective in prevention of Late Blight, and for sure not in curing.

So if you want to take a chance on it being Gray Mold and spray with the Ortho product, you can do that, with fingers crossed. And if it's a light case of Late Blight, who knows, it might even help.

And keep taking off affected foliage and disposing of it ASAP.

Hope this has helped.

Carolyn

    Bookmark   June 28, 2005 at 1:32PM
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kbarb

Carolyn,
Thanks for the information - I'll have to look up that Gray Mold to make sure I'm not mis-diagnosing. But thanks for the information.

[ I was teasing you there with the 137 for calling me Barb :-) ]

    Bookmark   June 28, 2005 at 8:07PM
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