What are these dark spots?

[Merediana]

I've found some dark spots on my leaves

The plants have been treated with fungicides twice, the last treatment was one week ago and I started noticing these spots 1-2 days ago. They are on more than one plant.



backside of the same leaf:

[gorbelly]

Symptoms are subtle right now. Could be the start of any number of diseases. Could be a nutritional issue. Could be damage from spraying a solution that is too strong or when the sun is too bright. Did you double check to make sure that your fungicide spray (I'm guessing copper due to blue residue) is at the right dilution and that any additives you may have used (soap, lime, etc.) were OK to mix with the fungicide and at the proper dilution?

[Merediana]

With the fungicide I'm quite sure that I used it right plus the german ones seem to be quite weak in general. I haven't added anything.

I think I do have a nutritional issue in general... Still figuring out how to fertilize them right in their pots as this seems much more complicated than in the ground. Last year it went much better, this year I purchased a fertilizer that should be even more suitable for tomatoes but obviously it is not...
I think I'll go back to the old one.

I hope it's no serious problem that might kill my plants.

Thanks for your help

[gorbelly]

What is the growing medium in your container? What is the fertilizer you're using, how much, and how often? How often and how much do you water?

[Merediana]

It's a typical german potting mix which contains mostly peat moss and I've added perlite.

I use a water soluble fertilizer which I add with every watering in a 0,5% dose (5g/10l) and so far I've watered twice a week - the weather is quite cold. Last year I did water daily at the same time but the plants needed it. Last year I used 10-15g/10l once a week.

This years fertilizer:

11 % Gesamtstickstoff (N)
11 % wasserlösliches Phosphat (P)
24 % wasserlösliches Kaliumoxid (K)
2 % wasserlösliches Magnesiumoxid (Mg)
6 % wasserlösliches Calcium
0,025 % wasserlösliches Bor
0,01 % wasserlösliches Kupfer* (Cu)
0,07 % wasserlösliches Eisen** (Iron)
0,04 % wasserlösliches Mangan*
0,004 % wasserlösliches Molybdän
0,025 % wasserlösliches Zink*

Last years fertilizer:

16 % Gesamtstickstoff (N)
- 9,7 % Nitratstickstoff
- 6,3 % Ammoniumstickstoff
8 % Phosphat (P)
22 % wasserlösliches Kaliumoxid (K)
3 % wasserlösliches Magnesium (Mg)
0,03% Bor
0,02 % Kupfer* (Cu)
0,15 % Eisen** (Iron)
0,05 % Mangan*
0,005 % Molybdän
0,015 % Zink*

This one doesn't contain Calcium which was the reason to switch. But I must say that I didn't see any negative effect last year. The only BER I got was on my in ground plants, not the ones in containers.

At the beginning of the season I tried an organic fertilizer on my pepper plants and soon got deficiencies because our water is very low in trace minerals That's why I feel like I need a fertilizer that has all the trace minerals added...

Edit: The reason why I add now fertilizer with every watering is that I've bought a mixing system that makes watering mouch easier. You just put it on your hose and it mixes the fertilizer in while watering. The options are: 0,2%, 0,5%, 1% and 2%. Both fertilizers can be used in watering systems.

[gorbelly]

If the weather is cold, perhaps you are watering a little too much? In containers, I usually don't water until I feel down a couple inches under the surface or unless it's very hot and I think the plant roots might need the cooling effect of watering. Too much wetness can cause the lighter/yellowish patches on the leaves. Also, cold can interfere with some nutrient uptake, which fixes itself when the weather warms. The cold can produce some purple in the stems and veins and some overtones of darker areas on leaves.

I would think you don't have too much to worry about right now. I would just prune off any leaves with spots or bad yellowing, continue to spray regularly as a preventative, be more careful with watering, and just watch things carefully. My guess is it will be fine. Aside from the mild yellow patches on some of the leaves, the foliage looks very healthy to me.

[Merediana]

Ok I'm probably just overreacting

But we had soooo much rain that I was really afraid of all those nasty diseases out there It seems to get better now but still with temperatures around 20-23°C maximum... I'm hoping for some sunshine.

I see a lot of dying tomatoes in the neighbourhood But well, it's mostly from those who don't have rain protection and don't spray.

In a german forum someone told me that I'm overfertilizing my plants.

http://imgur.com/Lhgu0Rm
http://imgur.com/uggzRNc
http://imgur.com/If88mmN

What do you think?

[gorbelly]

Originally Posted by Merediana

But we had soooo much rain that I was really afraid of all those nasty diseases out there

If the weather has been wet in addition to cool, even if the water does not go into your tomatoes, you are probably watering too much. I would make sure to check moisture levels deep in the pot before watering.

Originally Posted by Merediana

I see a lot of dying tomatoes in the neighbourhood But well, it's mostly from those who don't have rain protection and don't spray.

It could be disease. Cold and wet is perfect weather for a number of diseases, including the dreaded late blight. Or it could be nutrient problems due to the cold and being waterlogged. Also, excessive rain can deplete the soil of nitrogen, and nitrogen deficiency often looks like the plants are sick.

Originally Posted by Merediana

In a german forum someone told me that I'm overfertilizing my plants.

http://imgur.com/Lhgu0Rm
http://imgur.com/uggzRNc
http://imgur.com/If88mmN

What do you think?

Your plants look very nice and healthy to me. The big thing to worry about is too much Nitrogen relative to the other nutrients. That can produce big, green plants that have very few flowers and don't want to set fruit. But the proportions in your fertilizer seem to be OK for fruiting veg.

I don't know enough about liquid fertilizer to comment on the total quantity. This is my first year using liquid fertilizer. But frequent fertilization of container plants, especially when they are fruiting, is quite normal. You just need to think about the buildup of salts, etc. in the medium. For example, some people recommend watering with fertilizer at a diluted strength every time you water for a few times, then only water for the next few times, then repeat. Every time you water, you want to make sure to water deeply, until the water runs out of the bottom. This gives plants plenty of food, then flushes out any extra buildup. Other people recommend a very dilute amount of fertilizer in the water, but every time you water. Note that there's no set schedule for watering, though. You water only when the plants need it, always checking moisture levels first to make sure they actually need it, and water a lot/very deeply at that time. When weather gets very hot, they may actually need water once a day, even twice a day if the containers are small. But in Germany, with its more temperate weather, I would worry more about watering too much, at least until plants get much larger.

[Merediana]

They aren't waterlogged, they have some rain protection... Sadly the leaves get still wet when it is windy but I don't think that I'm watering too much. The containers are fairly small and I check them every time before I water them.

I think next time I'll flush them with pure water and than go on with the fertilizer...
Here some people recommend always watering first and using liquid fertilizer afterwards? Maybe this would be better?

Our neighbours are growing potatoes so this could be a source for diseases too

I'm now hoping for better weather I think this would solve a lot of problems...

[gorbelly]

Originally Posted by Merediana

They aren't waterlogged, they have some rain protection... Sadly the leaves get still wet when it is windy but I don't think that I'm watering too much. The containers are fairly small and I check them every time before I water them.

Once I saw the full plants, I thought they looked very happy. Not all the leaves can be pristine all the time, and your "problematic" leaves didn't really look bad to me.

Originally Posted by Merediana

Here some people recommend always watering first and using liquid fertilizer afterwards? Maybe this would be better?

Some people do that, too. Apply a dose of fertilizer at the recommended dilution after the soil is already wet. I would follow the directions that came with the fertilizer and only adjust if the plants look like they need more or less.

To be honest, it looks to me from the state of your plants that your routine is working for you.

[Merediana]

Thank you very much

[zipcode]

Err, that's just a very mild Magnesium deficiency. Like, I'd be happy to have so little in my containers. I bet they're on the sun facing part of the plant.

[Merediana]

Yes they are! So a slight dose of Epsom Salt would do the trick?

[zipcode]

Yeah, a teaspoon or so per plant. Note that affected leaves won't recover. It should just slow the effect. One of the reasons you're seeing them is because your plants are too healthy, no fungal disease of any sort, usually those lower leaves just go because of other problems before you see this problem.

[Merediana]

It's slowly getting worse... So far only on the old leaves.




Edit: I've signs of severe magnesium deficiencies on several plants that aren't tomatoes, it really seems tu be an issue here. And it's even worse with the in ground plants.