Tomatoes: Tomato Blight!

Jupiter, FL(Zone 9a)

How would I know what tomato blight looks like? And what would I do if I had it? (I don't think I do.)

Salem, NY(Zone 4b)


The word blight is a general one that many folks use to say their tomatoes are "sick".

But it has a very precise meaning in terms of diseases.

There are two tomato diseases with the word blight in the formal names.

The first one is Early Blight caused by the fungus Alternaria solani. Early Blight is the most common foliage in the US and indeed the world. It can occur at any time in the season but was initially called early blight becasue short season varieties are more susceptible to it.

I'm not going to describe the leaf lesions for the reasons given at the end.

Late Blight is caused by another specific fungus called Phytopthora infestans, which is the same fungus that caued the European potato famine. it too, can occur at any time during the season.

Now why have I not gone into great detail about the symptoms of either, which I could have?

Becasue it doesn't make any difference whatsoever what foliage disease you're dealing with, meaning, if it's a bacterial one you can't treat and it deosn't matter which fungal one it is becasue treatment is the same for all fungal foliage diseaes.

Late Blight is devastating and from the time symptoms appear until the plant is a mass of black stinking tissue can be only a matter of a week or less.

Late blight is not a problem in Florida.

Early Blight and the other common fungal foliage diseases such as Septoria Leaf Spot, etc are found in Florida. If you wish to start a preventative spray program I sugget using Ortho Daconil and I say Ortho becasue there are many different formulations of Daconil and all are not the right concentration for foliage disease prevention. Daconil is a synthetic but has lower toxicity than Rotenone, for instance, and can be applied up to the day of harvest.

Now if you meant somethng different by the word blight, such as Fusarium or Root Knot Nematodes or Gemini virus disease (big in FL) or any number of other diseases, then I haven't answered your question. LOL

But the word blight, to me, means the two foliage diseases with the word blight in them.


Jupiter, FL(Zone 9a)

Thank you for your explanation. I don't think I have any problems right now. My eight plants are in containers. There have been a few tomatoes with blossom end rot, but not many. And birds have taken a bite out of a few. The bottom leaves on some of the plants are a little yellowish and brownish. But the pots have blown over a few times (now they are next to a wax myrtle hedge for a wind break). Do you recommend preventative spraying with the Ortho Daconil, or should I just watch them for problems? Thanks again.

Lyndeborough, NH


Here a few pictures for you

(the last I knew this site was working)


Salem, NY(Zone 4b)

Byron and others,

Let me share with you and others my feeling about diagnosing diseases by looking at websites or even at tomato disease books.

The early lesions of many foliage diseases simply cannot be told apart.

Lesions are progressive, while pictures are static.

Maybe best to say that all foliage diseases show discrete lesions on the leaf surface while most systemic diseases don't.

And almost impossible to tell Fusarium from Verticillium from Root Knot Nematodes just from pictures. Need to cut the stems or in the case of RKN, look for the root nodules.

And there's limited usefulness, IMHO, in even making a definitive diagnosis with respect to future soil contamination, etc.

Goes along with my post about using Daconil for foliage diseases. Nothing to use against bacterial ones and doesn't make any differences re specific fungal diseases relative to Ortho Daconil.

I used to think it was important to be able to ID tomato diseases until the summer I spent working with the Cornell Coop Ext service who were doing a disease study of my heirlooms as compared to a number of hybrids I'd also planted for comparison.

That summer opened my eyes as to the utter frustration of making accurate diagnoses when in the long run it didn't really matter.

Just my opinion,to which I'm sticking. LOL


I believe my tomatoes have blight. I live in SE Georgia near the coast and it's pretty hot right now. We've had some rain but not alot. I've watered once a week while feeding miracle grow. If I treat with the Ortho Daconil will or should I continue to feed them miracle grow? Am I not watering frequent enough? This is my first garden and I've been real proud up to this point. We've been enjoying yellow and zucchini squash and my silver queen corn is comming along nicely. Any assistance would be greatly appreciated.

Benton, KY(Zone 7a)

Hi Bob! Welcome to DG!

The best thing you can do is remove the affected foliage and mulch your tomatoes with straw or grass clippings to prevent splashback of damp soil.

Not knowing what specific blight you are dealing with,it's hard to know what else to do.

Soil borne problems can be prevented by keeping the soil off your leaves,some nasties are air borne,and the only help you can give them is to grow them in containers on a covered porch.

Some blights look terrible,but your tomatoes will go ahead and produce.It sounds like your water/feeding program is ok.You may want to make some 'manure tea'and water your plants...leaves and all with it.This sometimes helps.

Clifton, NJ(Zone 7a)

I don't know what I've got,but it started with the leaves
on my plum (Roma VF) plants. From the ground up,first yellow/brown/black spots,rapid progression to dead leaves and to surrounding plants(Jet Star/Ramapo VF's).In 2 weeks the Plums are now vines(leafless)w/some fruit;others, leaves on top but fading fast. Last year nothing planted there (fallow ground).I remove N/G leaves,use Ortho Daconil. What helps?

This message was edited Sunday, Aug 10th 11:42 AM

Don, I have experienced the same thing up here in Sussex County. The fruit seems ok and is beginning to ripen (finally!!) But,the same description and the same beginning on the same type of tomato........

Everson, WA(Zone 8a)

can someone tell me how to ferment tomatoe seeds for saving please. Along time ago i remember reading to put them in a jar of water for a couple days but cant rember if the good seeds float or sink. my guess would be good seeds sink any help would be appreciated.

Murfreesboro, TN(Zone 7a)

eweeds, here's a step-by-step pictorial, from the journal of Dave (THE Dave - site owner, programmer, and gardener):

Orlando, FL(Zone 9b)

Here's a link to the Garden's Alive! website pest guide that gives information and some pictures of the diseases and pests in the gardens. Their catalogs actually contain better information and pictures than the website, but this may be of some help to the novice gardener:

They also tell you which of their products will help with the problem. If you're into organic gardening, I highly recommend this company. Good products, but they can be pricey. You can sometimes find the same or comparable products cheaper elsewhere if you look.

Pembroke Pines, FL(Zone 10a)

To Butterflygardnr:

Thanks for your hyperlink to "Gardens Alive" website pertaining to plant desease. I found it to be extremely informative.

Gastonia, NC

what causes the blooms to fall off my heirloom tomatoes ? is this a blight or disease or a chemical thing? please help

Warrenton, VA

Blossom end rot?Throw some lime into the soil mix when you plant, and you can, when the tomatoes start blooming, dust the leaves with it...and/or put a handful around the base of the plant. My dad taught me this, and I haven't seen this problem since I followed his lead...good luck to you!

Warrenton, VA

You know what? WIth all the stuff that tomato plants get, and all the stuff that you need to put on them, it is a wonder that we EVER get a crop of tomatoes. And, with the history of them going in and out of favor with the ages, it is even MORE of a wonder! Truly, the triumph of any vegetable gardener is holding that first of the season tomato in his/her hand.

Warrenton, VA

Neem Oil - I just discovered this incredible, organic product, and it is WORKING for my fungal problems! It first caught my eye regarding my Heritage Rose problems (Black Spot, Powdery Mildew, insects) and now it is working on the tomato problems! This might work well for you as well. It is not toxic, and I just made a solution to water my powdery-mildew-prone Magnolias with it for systemic use - there is reference aplenty to doing this. I dunno, maybe it would work with nematodes?
I plan to use a test plant for this if needed.

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