Yellow patches

My first year growing more than a couple of tomatoes.

I have about 20 plants, 6 different types, in rows about 80x400 (I dug up my lawn)

Yellow patches have appeared on all my different varieties of tomato in the last 24hrs... is it sun damage perhaps? Or some nutritional deficiency?

Thanks for your help :)

More yellow patches...

  • Are you positive it's only appeared in the last 24 hours? Deficiencies take more time than that to appear. And sometimes younger leaves are affected before others eg. in iron deficiency. Where are you, and what soil are you planting into? What nutrients are you using? Jan 17, 2017 at 7:04
  • 3
    I suspect it is a disease. Please take a photo on the underside of the most affected leaf to see its pattern and signs
    – Alina
    Jan 17, 2017 at 11:21
  • 1
    Have you had very wet or humid weather recently? Anything to see under the leaves as well as the yellow patches on top? what part of the world are you in?
    – Bamboo
    Jan 17, 2017 at 21:17
  • Did you have colder temperatures than has been usual, recently? This doesn't particularly have to do with my question, but I might suspect downy or even powdery mildew (although I don't see any powder, at this point). They can cause similar yellow patches. Jan 19, 2017 at 0:49

1 Answer 1


It is CHEMICAL (also called nutritional though plants don't need nutrition, they need proper chemicals and chemistry, they make their own food) deficiency. First, you absolutely have to test the pH. You could have plenty of proper chemistry in your soil but if that pH is off the plants won't be able to use Iron or Nitrogen for instance.

The other thing you should know is at this time your plant is putting its energy into the fruit, not the vegetative growth. If you were to increase the nitrogen right now your tomatoes would get bitter and tough. Your flowers would not set fruit. You'd get great vegetative growth with dark green leaves and NO fruit.

Test the pH. Tell us what you HAVE used how often for fertilizer. What have you added to the soil as well. What type of compost? Coffee grounds and that kind of thing? Ashes? What water are you using? Have you had a proper soil test? Tell us every little thing you've done or added to your soil, please.

I am seeing your tomato plants are in the garden soil and you are using either straw or pine needles for mulch? Your mulches are not decomposed. Anything dead has to be decomposed first and that takes feeding the decomposers who thrive on nitrogen. Decomposition will rob Nitrogen from use by your plants. Do not ADD nitrogen willy nilly or you won't get fruit. Get a pH test, get a soil test first.

Otherwise, when my tomatoes start producing fruit the vegetative leaves get wimpy looking no matter what. This mottling could be very normal OR it could be the beginning of mosaic virus from tobacco. ANY tobacco on hands, the smoke, will transfer this virus to your plants and certainly cause this yellowing. Keep smokers away from your garden plants!

And in that case, Alina is on the right track, a viral disease.

  • Nutrition is 'the process of providing or obtaining the food necessary for health and growth'. I'd say that plants' intake of chemicals necessary for food creation, and other natural processes fits that well. But good answer :).
    – J. Musser
    Jan 21, 2017 at 19:34
  • But humans do not understand the difference between nutrition and food. This is a big deal thing to understand as people automatically think nutrition is food, food is good and then way too much is given. Using the word nutrition is tantamount to saying FOOD. My big beef is getting people to understand plants are SO DIFFERENT to humans. Forget correctness! Therefore I don't say NUTRITION. I say chemicals.
    – stormy
    Jan 22, 2017 at 0:06

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