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Tomato stress symptoms

Hi everyone,

I have some problems with my tomato plants (cultivar Moneymaker) that always develop the same stress symptoms around 24 days after you see the first seedlings emerging. Before that, they look healthy and fine. The symptoms start on the cotyledones and are then appearing on the older leaves (egdes of the lower leaf side get purple and there are yellow . Plants are growing in 1l of potting soil at 24°C-22°C and 70% relative humidity. The way the symptoms appear made me assume that it is a lack of one or more nutrients but that doesn't seem to be the problem. I tried different fertilizers (slow release, specific commercial tomato fertilizer, a general commercial fertilizer and half-strength hoagland solution) but with each of these fertilizers, the symptoms appear exactly at the same time as they do in unfertilized plants. There is also no difference in plant size, which makes me think that 1l of potting soil is providing them with everything they need at this growth stage. The rest of the conditions look pretty much normal and are used in many studies. I attached some pictures as well. Many thanks in advance.


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  • pansyfacepansyface PEAK DISTRICT DerbyshirePosts: 20,088
    Maybe getting chilled, especially at night?

    Have you tried giving them a dose of Epsom salts?
    Apophthegm -  a big word for a small thought.
  • purplerallimpurplerallim LincolnshirePosts: 4,231
    The leaves of my toms that have layed against the greenhouse glass have done that too, I thought it was temperature caused as well.
  • Pete.8Pete.8 Billericay, EssexPosts: 8,485
    The purple/black marks on the leaves are due to a chill and nothing to worry about.
    I'd say carry on as you are. Black marks (like a bruise) on the stem of the plant may indicate blight.
    If you try to give supplements such as magnesium (epson salts) you have to be careful. If it's not needed then excess Mg can lock out Calcium which may cause blossom end rot.
    There's no need to fertilize the plants until the first tiny tomatoes start to form, then use Tomorite or similar
    Good luck
    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Hein_BlödHein_Blöd Posts: 5
    edited June 2019
    Temperature at night is exactly 22 C° and during the day it is 24 °C, which should be okay. The Hoagland fertilizer is supposed to be working great for tomatoes and I applied it in different frequency for different sets of plants, to exclude that it is simply an issue of too much/ too little of the right thing. It contains all macro- and micronutrients a plant could possibly need. I also tried two different light conditions and measured light intensity. They still developed the symptoms and they always develop them at the same time. I already know when I can expect the first symptoms to appear.
  • Hein_BlödHein_Blöd Posts: 5
    edited June 2019
    Pete.8 said:
    The purple/black marks on the leaves are due to a chill and nothing to worry about.
    I'd say carry on as you are. Black marks (like a bruise) on the stem of the plant may indicate blight.
    If you try to give supplements such as magnesium (epson salts) you have to be careful. If it's not needed then excess Mg can lock out Calcium which may cause blossom end rot.
    There's no need to fertilize the plants until the first tiny tomatoes start to form, then use Tomorite or similar
    Good luck
    I don't think it is a chill. They grow under absolutely controlled temperature. It doesn't get colder than 22°C. The fertilizer is a good point, I think the potting soil provides the plant with enough nutrients, otherwise I would have seen clear differences between unfertilized and fertilized plants. The plants are definitely stressed though. Some of these plants are already producing flower buds, which seems to be very early for that cultivar under these conditions (Seedlings emerged 24 days ago and get 16h of light a day) according to several articles I read.
  • HelixHelix 704m altitude...Posts: 631
    edited June 2019
    I wonder whether it’s the humidity? Humidity levels that are too high essentially suffocate the tomato plant. Transpiration processes cannot function or evaporate as effectively since the surrounding air is saturated with water molecules; tomato plants overheat from lack of evaporative cooling.  So lower leaves might be struggling as in the most humid zone? 

    Or of course it could just be the natural growing cycle of this variety.  As the plant grows it slowly allows the lower leaves to senesce and die off
  • purplerallimpurplerallim LincolnshirePosts: 4,231
    It does seem to depend sometimes on what cultivar you are using. Last year Alicante suffered badly in my greenhouse, but Gardener Delight wasn't so bad. This year it's a black tomato heritage seed type that has started doing this. Roma has no sign of it.
  • JennyJJennyJ DoncasterPosts: 6,038
    Maybe the constantly high temperature is too much and forcing them to grow faster than would be natural? 
    My toms (Gardeners Delight, Yellow Pear and Rosella) are outside and have been since mid-May, so night-time temperatures have been down below 10C and daytime (so far) rarely above 20C, mostly mid-teens.  And they're doing fine, green and healthy (except one plant whose leaves are starting off yellow then turning green, which is weird).  There are two or three trusses of flowers on each plant, and teeny tiny toms just starting to form on the lowest trusses (they had their first feed of half-strength tomato food last weekend).
  • Hein_BlödHein_Blöd Posts: 5
    edited June 2019
    Helix said:
    I wonder whether it’s the humidity? Humidity levels that are too high essentially suffocate the tomato plant. Transpiration processes cannot function or evaporate as effectively since the surrounding air is saturated with water molecules; tomato plants overheat from lack of evaporative cooling.  So lower leaves might be struggling as in the most humid zone? 

    Or of course it could just be the natural growing cycle of this variety.  As the plant grows it slowly allows the lower leaves to senesce and die off
    Interesting point. The humidity should be fine from what I read, but it is at the upper range and one of the view things that I haven't considered yet and that was always relatively constant. 

    I think it is normal that the cotyledones are die off after some time but especially the patterns that you see on the leaves in the picture do not look as if they were part of the normal growing cycle. Maybe there's another person here that grows Moneymaker and can confirm that.

    Many thanks to everyone for the great input!
  • GrannybeeGrannybee Sunny South EnglandPosts: 286

    I am no expert but I think :

    1. The pots are too small.

    2. The plants seem to be over-fertilised - no fertiliser required until the tiny tomatoes form and then only once a week

    3. The humidity is too high

    4. The small shoots on the main stem should be pinched out

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