Tomato leaves turning yellow - Ask Extension
Hello. My tomato plants seem to have all been hit by the same thing, despite being planted in different locations.
Starting at the lower leaves, the...
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Tomato leaves turning yellow #877156
Asked July 14, 2024, 1:23 PM EDT
Hello. My tomato plants seem to have all been hit by the same thing, despite being planted in different locations.
Starting at the lower leaves, they begin to turn yellow in the areas between the veins. They then turn brown and die off. I think it might be a magnesium deficiency, but I was hoping for your expert advice.
The upper leaves also have a slight speckling of tiny yellow dots. They have been getting watered, despite the drought.
Would you add epsom salts to their watering? If so, can you tell me how much and how often?
If it's a bacteria or fungus, how do I treat the soil to prevent it from returning next year?
Thank you!
Prince George's County Maryland
Expert Response
The leaf speckling, called stippling damage, is caused by sap-feeding insects or mites; in this case, the tiny size of the stippling spots suggests spider mites. Management tips can be found on the linked page.
We do see indications of nutrient deficiency in the foliage: possibly nitrogen for the solid-yellow leaf, and either magnesium or manganese for those showing yellowing with greener veining (called chlorosis). (Iron can cause chlorosis also, but occurs in the youngest growth, while magnesium and manganese occur in the older growth.) Epsom salts can remedy a magnesium deficiency, but will not address manganese deficiency if it exists, nor does it supply nitrogen.
Are all of the plants growing in the ground, or in containers? Were they fertilized earlier this season, and if so, what fertilizer was used? For plants in the ground, a laboratory soil test can help determine if any key nutrients are deficient, and if the soil acidity (pH) is outside of the ideal range for tomatoes (which impacts how easily roots can absorb nutrients), but that type of test will not work for potting soil.
While Epsom salts alone might be sufficient, you may want to use a more complete fertilizer instead, so it can also provide nitrogen and ideally manganese. The N-P-K needed is not exact (that is, you aren't limited to a formulation marketed specifically for tomatoes), but as long as the fertilizer contains micronutrients (which will include iron, manganese, and magnesium), that's enough. More information can be found on our Growing Tomatoes and Fertilizing Vegetables pages. (Or, for growing in pots, the page Maintaining Container-Grown Vegetables has a section on fertilizing.) If you do use Epsom salts, follow package label directions for dosage amount and frequency of use. Chlorosis can't always be reversed (that is, existing leaf symptoms won't resolve themselves, even if the missing nutrients are provided), but new foliage should remain an even green color if no further deficiencies persist.
If you notice other symptoms, our Key to Common Problems of Tomatoes page can help diagnose typical issues like fungal or bacterial infections. Soil treatment for such issues is not possible as fungicides won't be effective (and the pathogens are commonplace in the environment and could recolonize the site at any time), but in that situation, moving the plant's growing location for a couple years, or switching to growing vulnerable crops in containers, can help to bypass infection until it's safer to replant in the same bed. Some tomato cultivars also have higher disease resistance to certain pathogens.
Miri
We do see indications of nutrient deficiency in the foliage: possibly nitrogen for the solid-yellow leaf, and either magnesium or manganese for those showing yellowing with greener veining (called chlorosis). (Iron can cause chlorosis also, but occurs in the youngest growth, while magnesium and manganese occur in the older growth.) Epsom salts can remedy a magnesium deficiency, but will not address manganese deficiency if it exists, nor does it supply nitrogen.
Are all of the plants growing in the ground, or in containers? Were they fertilized earlier this season, and if so, what fertilizer was used? For plants in the ground, a laboratory soil test can help determine if any key nutrients are deficient, and if the soil acidity (pH) is outside of the ideal range for tomatoes (which impacts how easily roots can absorb nutrients), but that type of test will not work for potting soil.
While Epsom salts alone might be sufficient, you may want to use a more complete fertilizer instead, so it can also provide nitrogen and ideally manganese. The N-P-K needed is not exact (that is, you aren't limited to a formulation marketed specifically for tomatoes), but as long as the fertilizer contains micronutrients (which will include iron, manganese, and magnesium), that's enough. More information can be found on our Growing Tomatoes and Fertilizing Vegetables pages. (Or, for growing in pots, the page Maintaining Container-Grown Vegetables has a section on fertilizing.) If you do use Epsom salts, follow package label directions for dosage amount and frequency of use. Chlorosis can't always be reversed (that is, existing leaf symptoms won't resolve themselves, even if the missing nutrients are provided), but new foliage should remain an even green color if no further deficiencies persist.
If you notice other symptoms, our Key to Common Problems of Tomatoes page can help diagnose typical issues like fungal or bacterial infections. Soil treatment for such issues is not possible as fungicides won't be effective (and the pathogens are commonplace in the environment and could recolonize the site at any time), but in that situation, moving the plant's growing location for a couple years, or switching to growing vulnerable crops in containers, can help to bypass infection until it's safer to replant in the same bed. Some tomato cultivars also have higher disease resistance to certain pathogens.
Miri
Thank you so much for all this amazing information. I'm glad to hear that it's likely a nutrient deficiency rather than a fungal issue, which feels much tougher to deal with.
Most of the tomatoes are in pots, but I have about 5 other affected plants that share a large 2ft x 7ft raised planter.
Most of the tomatoes are in pots, but I have about 5 other affected plants that share a large 2ft x 7ft raised planter.
As for fertilizer, I have used Neptune's Harvest (liquid, 3-4-3, I think) in the past (maybe twice over the season so far). Most recently (one week ago, in response to this issue), I applied a general liquid fertilizer in the hopes it was a nutrient issue. That one was somewhere around 10-12-10, if I recall.
I also used epsom salts in my watering can once on at least some of the plants, but that was early in the season. I haven't been very consistent with which plants are getting fertilizer and which not unfortunately, but they all are affected.
I will look for a fertilizer that includes manganese.
Thank you!
Mike
You're welcome.
Liquid fertilizers act more quickly than granular (time-release, often in pellet form), but they don't last nearly as long. If since the start of the season (mid-May or so) a liquid fertilizer has only been used twice, then that definitely sounds like an under-nourishment issue, at least before your more recent applications. For now, the application a week ago might just need more time to begin working, though it will mostly benefit new growth since old foliage has limited capacity to re-absorb nutrients it had effectively run out of.
Miri
Liquid fertilizers act more quickly than granular (time-release, often in pellet form), but they don't last nearly as long. If since the start of the season (mid-May or so) a liquid fertilizer has only been used twice, then that definitely sounds like an under-nourishment issue, at least before your more recent applications. For now, the application a week ago might just need more time to begin working, though it will mostly benefit new growth since old foliage has limited capacity to re-absorb nutrients it had effectively run out of.
Miri
