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thatdamndonut

What the heck is it?

thatdamndonut
10 years ago

My tomato plants are looking fine - except for some leaves on on the bottom which have begun to spot and turn sick and yellow looking.
The smaller plant looks like it's just starting, but the bigger has on small limb which looks pretty bad. Any tips or pointers on what I'm dealing with and how to correct? When I look through pictures of ailments, all the pictures kinda blend together to me until it could just be anything. :)

Thanks!!

Comments (14)

  • uncle_t
    10 years ago

    Looks like blight to me.

  • digdirt2
    10 years ago

    First thing to do is remove the leaves from the plant as soon as any symptoms appear. Nothing is gained by leaving them on it.

    IMO it is neither Early Blight nor Late Blight but is most likely Alternaria, common in cool wet springs, based on what can be seen in the photo. The color of the plant over-all is pale. What and how often has it been fed in that container?

    You can find numerous pics of Alternaria on the web for comparison. I linked one below.

    Fungicides are the treatment of choice.

    Dave

    Here is a link that might be useful: TAMU - Alternaria

  • uncle_t
    10 years ago

    IMO it is neither Early Blight nor Late Blight but is most likely Alternaria

    Early Blight belongs to the Alternaria genus. I.e., Alternaria solani.
    Alternaria Canker also belongs to the genus Alternaria. I.e., alternata f. sp. lycopersici.
    Both are Alternaria


  • digdirt2
    10 years ago

    The Alternaria genus is a big genus and includes many different fungi and diseases for many different plants. So for a microbiologist it can be useful classification. For the average home gardener its use as a catch-all provides little useful info.

    "Blight" is another catch-all label that can mean many things and its use also provides no helpful information to the gardener. Most here, as the many previous discussions on this issue will prove, will repeatedly discourage its use as some sort of a diagnosis.

    Instead most, myself included, prefer to treat the different diseases as separate entities since they have different symptoms, different contributing factors, different specific causes, very different potential outcomes, and different methods of prevention and effective treatment.

    Late Blight is caused by Phytophthora infestans. Early Blight is caused by Alternaria solani. Southern Blight is caused by Sclerotium rolfsii. Alternaria is caused by Alternaria alternata f. sp. lycopersici.

    Dave

  • missingtheobvious
    10 years ago

    More regarding the use of the word "blight" by itself:

    Besides the three tomato diseases with the word "blight" in their common names, some people use the word to mean any and every tomato disease.

    I don't know exactly how uncle t was using the word in his first post.

    I have neighbors who use "blight" as a synonym for "disease." And as they don't discriminate between the different tomato diseases, they'll buy and use any garden formula which says it's useful for tomatoes, thinking it will solve every tomato disease problem. Since they haven't actually identified the disease, frequently the formula they're using doesn't do a thing for the problem their tomatoes actually have.

    The nightmare scenario is when someone (whether on GW or a neighbor trying to be helpful) diagnoses a problem as "blight" and the gardener in question finds something online about Late Blight, panics, and rips out all his plants ... when all the while it was something relatively minor like Early Blight or Septoria Leaf Spot that isn't remotely a plant death sentence.

    "Blight" can also be used -- at least around here -- as a generic term for "disease" in crops unrelated to tomatoes. I've heard it used at least a couple of times; the one I remember was mildew (not sure which type) on cucumbers.

  • uncle_t
    10 years ago

    Alternaria is caused by Alternaria alternata f. sp. lycopersici.

    Not true. Alternata f. sp. lycopersici is a species of Alternaria, where the latter is a genus of Ascomycota. Hence Alternata f. sp. lycopersici is the causation of Alternaria and not the other way round.

    For the species is a causation of the genus and not the cause of the genus. The same holds true regarding Alternata solani.

    Whether we chose to use "catch-all labels" or taxonomy, a true diagnosis can only come from a cultured sample of the fungus, observed in either a petrie or under a microscope--and not from photos.

    Whether it's "blight" or "canker", regarding Alternata solani and Alternaria alternata f. sp. lycopersici respectively, the solution is the same: garden hygiene and fungicide.

  • digdirt2
    10 years ago

    Sigh. Talk about a gross over-simplification. They are all the same disease, you can call it whatever you want, and all you need to do is have good garden hygiene and use fungicides.

    Gee, I wonder why the the commercial grower industry is investing millions of dollars annually to define the various diseases, understand the crucial differences between the causative factors, develop environmental controls to eliminate the development of them, and develop disease-specific fungicides.

    a true diagnosis can only come from a cultured sample of the fungus, observed in either a petrie or under a microscope-

    If that were true, given the frequency of the various diseases, then there would be little point in anyone growing tomatoes without direct access to a lab. We might as well all give up growing tomatoes.

    Fortunately it isn't true for any knowledgeable tomato grower who is often capable of distinguishing the plant symptoms one from another, treating them accordingly, and willing to help others rather than just tossing off a meaningless label at them and nothing else.

    Is a picture as good as seeing and examining the plant in person? Of course not. But we have to work within the limitations of this media.

    So if you wish to call all the issues in your garden "blight" and ignore the rest, fine. I, for one, prefer a more informed approach.

    Dave

  • uncle_t
    10 years ago

    You have been using the name of the genus Alternaria to describe a particular species from the genus--like referring to a Crown Victoria as a "Ford" in a lot filled with other Ford models. It is from this misuse of terms that the following statement later appears as if the species is the cause of the genus!
    Alternaria is caused by Alternaria alternata f. sp. lycopersici

    With all respect to you I'm not making this stuff up; you wrote it. Your free to believe it's a more "informed approach", but your mix up of genus with species was the only reason I chimed in after my initial post. If me pointing this out to you has caused you offense, that's unfortunate and it was not my intent.

    -Tim

  • digdirt2
    10 years ago

    So are you saying that your issue with my post is that I referred to it as the disease Alternaria rather than using the full name Alternaria Canker (aka Alternaria Stem Canker, aka Alternaria Tomatophilia, aka A. Stem Canker, aka etc.)?

    Alternaria Canker (see link I attached to the post above) is a common disease in tomatoes and is commonly referred to in its abbreviated form as Alternaria in the world of tomatoes. Yes is is the name of a genus but it is also used as a name of a condition in tomatoes (see numerous university extension websites that address tomato diseases).

    The use of a genus label (even a tribe, varietal, or species label) as also the name of a condition of a plant or person affected by it is fairly common in both botany and biology and in this case, far more informative than just "blight".

    Dave

  • uncle_t
    10 years ago

    So are you saying that your issue with my post is that I referred to it as the disease Alternaria rather than using the full name Alternaria Canker...?

    Yes of course, since you were attempting to DENOTE Alternaria alternata f. sp. lycopersici (Canker) from Alternaria solani (Early Blight).

    Consider your statement:
    IMO it is neither Early Blight nor Late Blight but is most likely Alternaria

    But Early Blight is ALSO Alternaria (Solani)! If you have a roomful of people with the last name "Jones" (genus), you're going to have to hard time distinguishing them without their first names (species). That is why I wrote in my second post
    Both are Alternaria.

    I thought you would have acknowledged this, yet the lack of use of species names continues with
    Alternaria is caused by Alternaria alternata f. sp. lycopersici Say what!?? What you probably meant was that Alternaria Canker is caused by Alternaria alternata f. sp. lycopersici.

    Am I splitting hairs? Absolutely not, particularly when you were attempting to DENOTE two (fungal disease) species of the SAME genus. This is why using the genus label in comparative studies of species within a genus is undesirable. Different genera? perhaps. Same genus? no. E.g., Alternaria alternata f. sp. lycopersici is a fungal disease but so is Alternaria Solani. If we just say "it's Alternaria", then which one? Which Jones? Which Ford? Looks like blight?........:)

    -Tim

  • lorabell_gw
    10 years ago

    Soooo...

    I'm having a similar issue, same looking leaves on a few of my plants.

    So, what would you guys be doing? I've been removing the leaves but it seems like I have a few more turning yellow this morning.

    Is there a fungicide you recommend?

  • edweather USDA 9a, HZ 9, Sunset 28
    10 years ago

    I use Daconil before our usual late blight time in mid-late summer.

  • skeip
    10 years ago

    I don't recall reading postings from uncle t in the past, so I say welcome, and wow, you seem to have some impressive knowledge on disease pathology. Dave has been providing excellent knowledge on a wide variety of subjects for as long as I have been visiting this forum, and also has an excellent knowledge of disease pathology. I have learned a lot from him. I have a degree in Horticulture, but practices and ideas change in this area of knowledge as they do in all.

    The massive late blight epidemic of a few years ago forced many people to reevaluate their cultural practices, and increased disease knowledge and treatment for a great many people.

    I am pleased to see another knowledgeable person posting to this site, it only adds to the quality of the whole. I believe that we all have lots that we can learn, and lots that we can teach.

    In all public forums where there is no ability to judge inflection and intention, the posibility of misunderstanding intent is increased greatly. We must all consider our words carefully so as not to be misunderstood, and risk offense.

    Again, I am pleased to have two such knowledgeable individuals posting on this forum.

    Steve

  • digdirt2
    10 years ago

    Then my apologies for not typing out Alternatia Canker and only referring to it as Alternaria. Although as I said, doing so is a common practice in the context of tomato-growing forums and might well be considered splitting hairs. The link attached to the post made it quite clear that Alternaria Canker was what I was talking about. But if one didn't bother to click on the link I attached then they would have no way of knowing that.

    ________________

    Lorabell - there are literally hundreds of discussions here about your question on fungicides and Daconil is considered the fungicide of choice unless one wants to be totally organic. In that case the options are one of the several copper-based fungicides or selective use of Actinovate and/or Seranade.

    Dave

    PS: thanks Skeip. :)

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