just how destructive is late blight?

[tjg911]

due to my inattention i had LB on 8/20 but it wasn't until 8/24 i saw and realized this is LB. i know what the damage to the leaves and stems looks like and the gray fuzzy spores under the leaves so i am really sure it is LB.

on 8/23 i sprayed all 8 plants with fish milk and on 8/26 i sprayed again but just milk and water no fish fertilizer. no spraying since.

all my plants are still alive tho most lost 75-90% of the foliage, aunt gertie's gold still has good amount of foliage, and some plants have new flowers. about 8/29 many fruits were light green so i picked 30-40 figuring the plants would be dead in a few days and maybe some of them would ripen. all ripened fine as far as color but most are inedible, they are sour or hard or mealy or some combination. i have made 3 batches of pretty good sauce so far and have dozens more tomatoes so i'll probably get a lot of sauce.

about 9/4 i picked more fruits some were coloring up on the vine. i removed all fruits that have LB rot on them and they went into the trash can.

today all 8 plants are still alive, as i stated some have new flowers and many of the fruits do not have any LB lesions and are ripening.

here's an ironic twist, in 2009 the year of massive LB, prue was the last plant to die, it was labor day about 6 weeks after infection and fish milk spraying. this year prue lost the most foliage the earliest from LB while other plants did not look that bad. but here's the odd thing, all the prue tomatoes i picked, free of any LB, have all ripened and so far every one was good to eat vs all the others that were not! the taste is not 100% but darn good vs the 7 other varieties you wouldn't want to eat.

so the point of all this is "is LB fatal 100% of the time and if so in what time frame?". how can i have all 8 plants still alive 2 1/2 weeks after LB struck? i used a milk spray twice and never used daconil. it's rained a few times so the plants have been wet over night but since 8/20 it has been warm (70's some 80's), sunny and low humidity.

tom

[maf]

Late blight needs very specific conditions of humidity and temperature to be able to proliferate, so it could be possible that a period of low humidity could halt the spread. Plants that already had serious stem lesions would not usually survive though.

Also, with the gray fuzzy spores showing, for the purposes of elimination it might be worth checking out (if you have not already considered this) the symptoms of the fungal disease called botrytis aka grey mould/gray mold. This is a less aggressive problem than late blight that looks somewhat similar.

[b54red]

Tom this is the fourth time I have had LB and it is always a disaster but the damage can be slowed or limited if you act quick enough. I have found that it usually hits me when we have a long period of rain and my usual Daconil sprayings are not possible. The one thing that I have found that helps is to spray with the dilute bleach spray that I have mentioned many times. It seems to have the ability to kill the spores so they are not spread and if it is Gray Mold then it is even more effective. During rainy spells the more often you can spray the bleach the better the results. I find that when I slack up on the spraying is when the real disasters strike.

The first time I had LB it killed every plant within two weeks because I only used the usual fungicides after it had taken hold of the plants and they were useless. Once you get it on the plant it has to be stopped quickly or it will take out most or all of your tomatoes. My problem is I always lose some of my plants because I am too late recognizing the problem and attacking it. Those first few plants that I realize have LB are frequently goners; but if I start spraying them and all the other plants every few days with the bleach spray most can be saved. I have been better the last few years and have been able to keep more of my plants alive and somewhat healthy and productive. I only had LB once before I started trying to grow fall tomatoes every year. Now it seems to hit every time we have extended rainfall during the later part of the summer or fall. Oh well I guess it is better than no tomatoes at all after mid July which is what I used to have.

maf, I agree on the stem lesions. Once they show up it is usually the death knell for the plant. I have had a few with the lesions remain alive for a month but only a few.

[stonysoilseeds]

i have a questup b54red can i use the dillute bleach spray as a pyotectant against late vlight like spraying ar 1 ot 2 week intervals... its too late for me this year but im planning for 2013

[stonysoilseeds]

whats also strangeto me is that my sungolds which are the only hybrid i grew is the only variety out of over 65 were the fruit have not been affected by the blight

[tjg911]

sun gold held up well in 2009 but took it hard this time. i don't think that variety has any advantage because it's a hybrid - i think it is the luck of the draw. i'll supplement that with how well sun gold and prue held up in 2009. this year prue was hit fast and hard and is now done, the plant's alive but no fruits left, and sun gold held up for a while but is just about done almost no fruits left while other varieties are doing better than those 2. this time vs last, prue got it the worst and is in the worst shape and lost the most tomatoes but does have the best tasting of those that are edible.

i have thrown away dozens of tomatoes, probably close to 100 off 7 plants, i am excluding sun gold my comment is for non cherry plants. i'm still seeing LB on fruits that were ok a week ago. no foliage is showing any new LB. the stems of many plants had LB lesions and may still have them, i am not looking too closely at the plants anymore. at this point i consider myself lucky to get any fruits that are edible. some sun gold are ok but not up to their normal great taste same as the prue fruits but were edible. i had an aunt gertie's gold, black krim and earl of edgecombe that were so so, normally i'd say not so good but now about as i can hope for until next july or august. the10-12 prue on the table continue to ripen and are darned good but again not up to what is normal.

so it seems that LB does not always kill the plant in a few days and it is possible to keep the plant alive tho yields are greatly reduced and flavor can range from terrible to good but not as good as it should be.

tom

[stonysoilseeds]

maf i wish it was something else besides LB as i truly have never seen as destructive a disease .. last sunday with theexception of 2 plants all looked quite healthy and loaded with fruit... within the 5 days it has infected 35 rows of my plants ... i am taking most of them out now.. i think botrytis pathogen infects dead tissue where LB infects live tissue and as you stated is far more of an aggressive pathogen... we had a very dry summer but we had rain last saturday and the conditions were favorable for the pathogen phytopthorainfestans to infect with a vengeance.. i read that in england and parts of Europe there are strains of this pathogen that can reproduce sexually where it can overwinter on non living tissue.. that strain i believe hasnt reached the USA yet..

[stonysoilseeds]

red i am very intersted in your bleach solution as a foliar display for next year... at what concentration should thebleac be dilluted to..... i think i will spray my plants every few days after transplanting... i really dont ever want a LB problem again..... i have a small taste of what Ireland went thru during the potato famine era

[b54red]

Stony, the bleach spray is not a preventative other than the fact that it will kill most spores on the plant already. It is gone within minutes of spraying and has no residual effect so a preventative like Daconil can be used once the leaves are dry from the bleach spray.

I add 8 ounces of regular bleach (Clorox because of consistent quality) to one full gallon of water and then add a few drops of dish washing soap as a surfactant. I prefer to use it very early in the morning or very late in the day to reduce the chance of leaf damage to healthy plant tissue. Use a fine high pressure spay and hit all surfaces of the plant and both sides of the leaves. Usually if a disease is not systemic then the diseased leaves will shrivel up and die within a few days while healthy leaves are unaffected. It can be used as often as necessary. I have used it every other day for as long as two weeks without any ill effects but I'm sure there is a point where it could cause some damage if overused. I try to use as fine a spray as possible so there are not puddles left on many of the leaves which could cause a problem if the sun hits them.

[carolyn137]

No, Late Blight does not always kill ASAP. Below I've linked to one of the several Cornell sites about Late Blight and on the right hand side there are others links as well.

And I don't know if it's the one I'm linking to or one of the other ones that does discuss the timing of LB infection.

Infection with any pathogen is quantitative so the more spores the worse the outcome and the quicker the plants go down.

I've seen a few posts in various threads here about LB recently that said that infection was transmitted from plant to plant. But that's not true unless the person working with the plants manually did that.

The two ways that LB is spread is by wind and embedded in raindrops, and that's it.

Many antifungals mentioned at the various Cornell links are only available if one has a license to purchase them. And there's one link that discusses organic growing and LB. But for most of us the most effective preventive is Daconil.

[ginger2778]

Originally Posted by carolyn137

No, Late Blight does not always kill ASAP. Below I've linked to one of the several Cornell sites about Late Blight and on the right hand side there are others links as well.

And I don't know if it's the one I'm linking to or one of the other ones that does discuss the timing of LB infection.

Infection with any pathogen is quantitative so the more spores the worse the outcome and the quicker the plants go down.

I've seen a few posts in various threads here about LB recently that said that infection was transmitted from plant to plant. But that's not true unless the person working with the plants manually did that.

The two ways that LB is spread is by wind and embedded in raindrops, and that's it.

Many antifungals mentioned at the various Cornell links are only available if one has a license to purchase them. And there's one link that discusses organic growing and LB. But for most of us the most effective preventive is Daconil.

Please Carolyn,
How does LB get into the raindrops?
-Marsha

[carolyn137]

Originally Posted by ginger2778

Please Carolyn,
How does LB get into the raindrops?
-Marsha

Interesting question Marsha and I'll give you two answers. One from my observations, which are the same as many others, and a second from doing some Google searching.

If spores for any of the fungal diseases that start out infecting foliage, meaning Early Blight ( A. solani), Septoria Leaf Spot and Late Blight ( P. infestans) land on the leaves and conditions are dry they can't sporulate b'c they need moisture to do that. And that can be rain or fog or dew. I once knew how long the spores had to be in contact with moisture , possibly a few hours, but didn't check that out.

Almost everyone I know tends to see foliage infections after rain, thus the question posed by you.

It turns out that raindrops start forming in clouds around dust particles, as the nucleus, if you will, and as they fall become larger and can pick up "stuff" as they fall, such as pollen grains and more. One can find links to other fungi that explode their spores into the environment and they too can be found inside rain.

Here's a few links for you to read:

http://www.google.com/#q=dust+partic...gc.r_pw.&cad=b

http://www.ehow.com/how-does_4911272...car-dirty.html

http://physics.aps.org/story/v7/st14

From doing a general Google search I found that since I'm NOT a physicist I really couldn't understand quite a bit about the physics of the process, but at least the above links, and there are many more, that I think are very convincing as to what can be found in raindrops and by that I mean the fungal spores of several tomato diseases. probably some of the bacterial diseases as well, but I didn't do any searching about those.

Just be glad that in FL you don't have to deal with LB as many others in certain areas of the country have to do.

[ginger2778]

Thanks for these interesting links.
What I thought was the most interesting thing about raindrops was that they only get to about 1mm in size before they start falling from the cloud, and they gather the rest of the moisture to form a raindrop size that we see by the time they land , in just those few seconds. It looks like the spores are already in the air, and the raindrops pick them up as they fall.
See that's why I like this website. It's all the learning.

Oh and I am definitely glad LB isn't a problem here, because it's enough with the millions and millions of whiteflies and that lovely TYLCV they give the plants.
-Marsha

[Save$]

Originally Posted by carolyn137

Interesting question Marsha and I'll give you two answers. One from my observations, which are the same as many others, and a second from doing some Google searching.

If spores for any of the fungal diseases that start out infecting foliage, meaning Early Blight ( A. solani), Septoria Leaf Spot and Late Blight ( P. infestans) land on the leaves and conditions are dry they can't sporulate b'c they need moisture to do that. And that can be rain or fog or dew. I once knew how long the spores had to be in contact with moisture , possibly a few hours, but didn't check that out.

Almost everyone I know tends to see foliage infections after rain, thus the question posed by you.

It turns out that raindrops start forming in clouds around dust particles, as the nucleus, if you will, and as they fall become larger and can pick up "stuff" as they fall, such as pollen grains and more. One can find links to other fungi that explode their spores into the environment and they too can be found inside rain.

Here's a few links for you to read:

http://www.google.com/#q=dust+partic...gc.r_pw.&cad=b

http://www.ehow.com/how-does_4911272...car-dirty.html

http://physics.aps.org/story/v7/st14

From doing a general Google search I found that since I'm NOT a physicist I really couldn't understand quite a bit about the physics of the process, but at least the above links, and there are many more, that I think are very convincing as to what can be found in raindrops and by that I mean the fungal spores of several tomato diseases. probably some of the bacterial diseases as well, but I didn't do any searching about those.

Just be glad that in FL you don't have to deal with LB as many others in certain areas of the country have to do.

You know, I don't recall my LB after a rain, but with prolonged cool damp temp. Like the ones we get mid August when we start getting ground fog and everything is wet with due in the morning. Never put that together. Thanks. Looks more and more like I either have to get my crop to mature before mid August, use blight resistant varieties, or grow them under some sort of cover. I don't think there is any chance that the box stores will stop importing seedlings from areas with infections.