can my plants survive late blight?

13 years ago

I'm surprised not to see recent posts about late blight, which is decimating tomatoes in my neighborhood again this summer. We have had our typical June coastal fog lasting pretty much all day for the past 6 weeks, perfect conditions for it to develop. Plants are damp from around midnight until 3 the next afternoon. Everything looked pretty good when I left for a week's vacation, but when I came home end of June most of my plants had the grey/brown leaf spots, some stems getting brown and brittle.

I thought for a while some plants might survive as I kept removing the affected leaves, but now there is only one left, a Better Boy, that is not seriously damaged. Much green fruit on the others, and it is beginning to develop the brown, hard spots. Other varieties I have planted are Stupice, Sungold, Early Girl, and Druzba. I had heard that Early Girl and Stupice might be a bit resistant, but an Early Girl was the first one hit, Stupice a few weeks later (and those are planted close to each other).

But there is new growth on virtually all the plants (only a dozen plants) and so I am wondering if I should just keep taking off the diseased parts and hope that with drier weather (typical later in summer here) some plants might recover and still produce some fruit. We can typically grow tomatoes into October, even November, in this area, so there's a long potential season ahead.

Have others had plants come back from serious infection to produce some fruit?

Until last year, I never had serious problems with disease in tomatoes.

I have peppers and eggplant planted in with the tomatoes and neither are affected, even though they're solanaceous. Also every year I get dozens of volunteer tomatillo plants which are very vigorous growers and producers. I wonder if the spores could be overwintering in tomatillo seed in the beds. Have read both that spores don't overwinter (that infection has to come from new infected seedlings) and that spores DO overwinter--in soil, in seed. Which is correct? Does anyone know?

I could use some good advice about what to do now that it has struck. Thanks for listening....

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Comments (2)

lionheart_gw (USDA Zone 5A, Eastern NY)
13 years ago
Hi,

Are you sure it's late blight? If you can post some pics that would be more helpful.

It sounds like it could be late blight but, after 2 weeks, you should be seeing lots of plant death. Also, when I had LB last year, I recall a fetid, rotting flesh type of smell coming from the plants and fruits. Your mileage may vary on that. :-)

Anyhow, if it is late blight, the plants and any fruits are pretty much doomed. Oh, you can probably cut off any spots on the fruit and eat them (LB is not harmful to people), but I can't imagine anything more unappetizing. Otoh, I know how badly folks want those tomatoes, especially after all the time and effort you put into them.

If you had planned to can the fruit or make sauce, forget about it. Late blight alters the pH of the fruit and, if processed and stored, can lead to spoilage of the product, perhaps encouraging the growth of other organisms that can make you sick.

Late blight spores that produce asexually cannot overwinter in places that have freezes, UNLESS you have potato tubers in the ground. Asexually-produced LB spores can only survive in living tissue.

If underground potato tubers are not removed, the spores may overwinter in the potatoes. Since most parts of the country have freezes, it kills tomato plants (above ground plants), thus killing the plant tissue and the spores cannot survive. Potatoes, on the other hand, being underground and not killed by freezes, can host the LB spores. This is why it's important to dig up and destroy infected potatoes.

This type of LB (the asexual reproduction type) cannot be transmitted via seed. This is the most common type of LB found.

To further complicate things, there is a so-far very small number of LB spores that reproduce sexually, and they can survive without living plant tissue. These are very rare and uncommon enough that there is no reason to suspect that currently.

If you get a confirmation on the LB, the plants and fruits should be bagged in plastic and sealed. You can put the sealed garbage bags in the sunlight for a few days to heat them up, which might help destroy the spores, then put them in the garbage. As you probably know, do not compost any part of the plant. This is especially important in your part of the world, where it's warmer.

If it is LB, you have my sympathies. I and many others lost every single tomato plant to LB last year, usually before we got any tomatoes at all. [It didn't infect the peppers, however.] We know how sad it is.
sheloolie
Original Author
13 years ago
I'm pretty certain it's late blight, I'll post a couple photos I took today, after I removed another big can full of damaged stems and leaves.

Last year I started some plants in April and then more in late June--the late ones were infected but they were not killed and they came back to produce reduced crops in late September and October.

To address the issues you raised--last year I did eat the undamaged parts of affected fruit--and the damaged parts were gross I remember, hard but black and sort of grainy. Never noticed a rotting smell, any smell other than normal tomato aroma. I wasn't planning on canning this year. I don't grow potatoes, that won't be a problem for next year. We rarely have hard freezes, maybe once in 20 years.

Hmm, not seeing an obvious way to post photos in this follow-up. But my plants look just like all the photos I see in sites on late blight, the same spots on the leaves and dark areas on stems and dark, slightly sunken hard areas on the fruit. And then the foliage dies and dries up.

Thanks for the sympathy....it's pretty sad, all right.

I have a friend, a commercial organic grower, who started spraying his plants with compost tea almost daily back in May, and does not have any blight at all this year (about 100 plants). He swears by compost tea as a preventative, says it won't work though as a treatment once the fungus gets going.

Thanks much for your information. I have kept the cuttings out of the compost, been putting them into our green waste bins to be collected and then wondering what happens when they are turned into mulch by the county....not room enough in the regular garbage....we are limited as far as garbage, local government trying to divert more waste into recycling and green waste, which is a good thing in principle.

Can't see how to add photos in a follow-up, sorry.

Thanks again. Tomatoes are summer, hard to give that up....
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The issue is survivability of the fungal spores from plant through composting and then in the tea. There are so many variables, coupled with an unidentified pathogen, and uncertainty of whether the composted leaves were even infected, that I don't believe anyone can suggest with any certainty what the probability of spore survival in your situation will be. So, it's a crapshoot. Reports of fungal spore destruction during composting of tomato vines infected with either late blight fungus (Phytophthora infestans) or early blight fungus (Alternaria solani) are varied. Spores of both can survive a year or more on infected plant tissue and in soil. Most reports indicate that spores associated with early blight is destroyed in hot thermophilic composting followed by adequate maturation. Spores associated with late blight, however, have been reported to survive composting. As for a compost extract or tea, I've not seen anything that indicates what impact the brewing process may have on spore survival for either. If the composted leaves were disease and spore free, the risk would be probably non-existant. There have been a lot of tomato plant residues composted by many gardeners without problems following. The concern arise if there were spores present, either on the plant material or in any attendant soil that came with that material. If the plant materials that you composted were infected, there is a clear risk. But, I don't think with what you've provided anyone can gauge whether the risk is high or medium or low.
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In the 'old days', many of the tomato plants have a lot more natural protection againt any blights. Today, with all the hundreds or varieties, its very hard to know which will grow well in a specific area. I recall growing stuffing tomatoes one year. Kind of like a cross between a big bell pepper with an empty cavity inside except for the seed cluster. The stuffing tomatoes looked good at first, but once the started to ripen to red, they got small spots on the skins that destroyed them very fast. If they were picked before the spots appeared and brought indoors, washed and allowed to sit on a counter overnight, the next day they would have many bad spots that quickly consumed them. Never again will I plant a stuffing tomato. My two favorite choices for tomato seeds is Totally Tomatoes and Tomato Growers. Both offer many kinds, and some are highly resistant to blights. Of course the store boughts are like baseballs and can take a lot of banging around, but thats fine if they are intended to be handled a lot and shipped a long distance away.
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OK that's what I thought. Even with a very small chance of late blight being in my tomatoes, I wanted to make sure because I will be trading off a lot of seeds and wouldn't want to transfer anything. I'm aware that there are other diseases that can be transmitted by seed, but I just wanted to rule out late blight since it's been such a problem this year.
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can my plants survive late blight?

Comments (2)

lionheart_gw (USDA Zone 5A, Eastern NY)

sheloolie
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can my plants survive late blight?

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lionheart_gw (USDA Zone 5A, Eastern NY)

sheloolieOriginal Author

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sheloolie
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