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Location: north Italy (Alps). Asking for my dad.

My dad has planted some 20 tomatoes of various type in his garden, in a spot with around 8h or sunlight and automatic watering through a drip-tube at the base. He sometimes alternates by planting potatoes, and in spring before planting he usually turns the earth around and adds some new/fresh earth/compost. He has been doing this for years and always has good harvest.

This year he noticed an issue on some of the plants: the leave starts to dry up and wither, and some fruits starts to have some spots as if they are starting to rot. So far it seems as only the regular round tomatoes are affected by this, but it seems to be spreading.

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Reading up online about it could be overwatering, but we doubt it is that. We read it could be some apical rot caused by lack of calcium, but we are not sure.

What is causing this? Can the plants still be saved? How can this be prevented next year?

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  • Potatoes and tomatoes are in the same family; it's recommended that they not be planted in the same ground without a (usually) three year rotation with plants of other families (for example, tomatoes/peppers/potatoes one year, root crops the next, melons/squash/cucumbers the third year). Has your father been doing this?
    – Jurp
    Jun 2, 2022 at 11:17
  • It is like a plot of land, roughly on one half he plants tomatoes, on the other half potatoes. The next year he then switches places and plants the tomatoes where the potatoes were, and vice versa. In between the plants he also plants some basil, onions, salad and such smaller things. Will tomatoes and potatoes use up the same nutrients and make the ground "bland"?
    – pazi__fisch
    Jun 2, 2022 at 12:36
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    You can get away with that (planting the same plant-family year after year in the same ground) until you can't - the reason for rotations through other families of plants is to help break disease life-cycles - once a disease has become established it's very hard to get rid of if you don't change what plant-family is growing there for long enough to disrupt the disease.
    – Ecnerwal
    Jun 2, 2022 at 19:30

2 Answers 2

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It actually looks a lot like a Torradovirus. I've been reading up on that lately, and it can result in the dark leaf edges and strange stuff on the fruit. I'm not sure if it contributes to fruit rot, however (but from the pictures I've seen, I wouldn't be surprised). The affected fruit on the right looks closer to it than the one on the left.

Here's a page that tells about these viruses: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/tomato-torrado-virus

Here's a relevant quote from that page:

". . . symptoms . . . begin with the appearance of chlorotic spots at the base of the leaflets, and these later develop into necrotic spots and/or conspicuous shot-holes, giving the leaves a burned appearance . . . Fruits can also suffer necrotic lesions and cracking, making them unmarketable. "

Alternatively, it's possible that you over-fertilized your plants (probably with nitrogen) or something.

Regarding your question about calcium, calcium, magnesium, nitrogen, and potassium all need to be in proper balance. I'm not sure if an imbalance there could cause those specific symptoms (I've never seen that happen, anyway, but it's possible). More likely, you'd just get blossom end rot or a fungal disease.

I learned about this virus by reading about tomatoes that were resistant to it.

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  • As you mention, and comparing with other pictures online, it seems to me it may be some kind of fungal disease (blight).
    – pazi__fisch
    Jun 2, 2022 at 12:46
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Going to a garden center they claim it's peronospora (late blight), and as a remedy they recommended to spray the plant with verdigris fungicide.

They also recommend to cut off the infected parts and not throw them into the compost/mulch.

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