yellow spots on tomato leaves

I'm getting conflicting diagnoses. Is it the start of blight? Mosaic virus ? Bacterial infection ? Or a deficiency in something ...magnesium ?

This was a recent discussion on this subject-my feeling is you will find the answer there

http://www.gardenersworld.com/forum/fruit-andamp-veg/tomato-leaf-problems---help/4527.html

If not italiophile will be along at some time -he is the tomato guru

Are these actual yellow spots, or a more general yellowing between the leaf veins?

They are seperate fairly round , pea sized spots. I am removing quite a lot of the leaves as the light levels are so low and to improve air circulation.... keeping greenhouse door open plus windows.... should I close at night ?

joanna, can you post a photo? It's always easier if we can see the probem. Doesn't guarantee a diagnosis, but it helps. Are the spots actually yellow? Or a pale brown/fawn, as in necrotic (dead) leaf tissue?

And when you say the light levels are low, how much sunlight are the plants getting?

With the summer we are having sun would be a real bonus ! The spots are more fawn coloured.... would love to post a pic... not possible at the moment sadly. The outdoor plants are fine , so far.They have also started fruiting whereas the greenhouse ones are still very green. 

Do the spots look like this?

Not as extreme ...those are dead patches and maybe mine will become like that but in size and shape they are similar. I am really grateful for your input Italophile ..thanks.

Yes, that's necrosis, dead tissue. It can be nothing to worry about in terms of disease. Fertiliser burn can cause it, and sunburn (though probably not in your case!)

Are the spots on the top or underside of the leaves? And where are the leaves on the plant? And, last question, is there any sign of a darker spot forming in the middle of the current spot?

The spots are yellowish on the top of the leaves and brown on the undersides and leaves are affected from top to bottom of the plants. The variety worst affected is Brandywine Pink. No sign of darker spots in the patches.

Brandywine Pink? It is a Potato Leaf? With the almost smooth, slightly scalloped edges? As distinct from the traditional saw-tooth edge of a tomato leaf? Glorious tomato. Possibly the best I've ever tasted. Only Marianna's Peace comes close, I think.

It's so hard to know without actually seeing anything. Did you notice whether the problem developed from top to bottom or vice versa? The brown underneath hints that it might have developed on the underside. Septoria Leaf Spot does that and it, along with Early Blight, are the most common fungal problems in the home garden. They both tend to start from the bottom of the plant - the older leaves - up. EB is more apparent on the top of the leaf and pretty quickly develops a "halo" around the spot.

You might not want to, but I'd be inclined to leave one leaf in situ and watch it. If it's SLP, you'll see little pin-head type mini-bumps develop inside the brown patch. If it happens to be SLP it won't terminally damage the plant if you contain it. None of the fungal problems do massive instant damage - except Late Blight, which will kill a plant in weeks - and the onset of cold weather usually terminates things before the fungal problem does.

Sorry I can't be more specific. Without an image, it's sort of guess work.

I overlooked your earlier query about doors and windows. Air circulation is an absolute priority in greenhouses. A closed environment can be an incubator for all sorts of nasties.

Just an idea - it could be scorching - the sun has been very hot indeed for short periods on the few occasions that we've seen it (it's just the cloud cover that's keeping temperatures down).  If the tomatoes had got some water splashed onto their leaves and then the heat of the sun through the glass ....?  

I've seen some nasty cases of sunburn on people this year, believe it or not - pale skins with no protection, 20 minutes of scorching sun

I wondered about something like scorching but the symptoms are all over the plant, top to bottom. Scorching is usually confined to affected leaves.

Any of the fungal (or indeed bacterial) problems develop their symptoms pretty quickly. That's why I suggest leaving a leaf or two in place to see what transpires. It would be a pity to defoliate for, ultimately, no good reason.

If I were to ( on one or two plants) remove all the affected leaves could the plant still function with maybe only a very few leaves and plenty of potential fruit ? I love the potato leafed Branywine too ...sometimes difficult to get it to set fruit and therefore not the most prolific plant but what flavour !

The plants need the leaves for photosynthesis. Take off too much foliage and you run the risk of the plant basically shutting down.

The thing with the fungal and bacterial diseases is that the symptoms develop on the leaf. They don't just begin as a spot and remain so. The spots get darker, crustier, develop tiny concentric rings within the brown spots in the case of Early Blight (as well as a yellow "halo" around the spot), and the wee pimply pinpricks I mentioned in the case of Septoria Leaf Spot. The spots/patches spread across the leaf, there is yellowing and withering, the signs are umnistakeable with all the diseases.

Trouble is, I'm not sure that you have a disease problem. Is there absolutely no way of posting an image?

Yes, the Pink Brandywine is about the most fickle of toms. Neurotic probably best describes it. It won't set fruit in any sort of high-ish temperatures or humidity. When I used to live in Sydney I had to grow it as an autumn crop because it couldn't cope with the hot, humid Sydney summers. Glorious flavour, though.

 hope this helps! this is the top side & on the reverse the spots are brown

Is this what the brown spots on the other side look like?

 Or this?

More like the top one . I'll see if I can get you a pic.I've removed the worst of the leaves to try and slow down the spread, increased the airflow ,decreased the watering and feedingand will keep an eye on it all ... thanks so much for all your help.

 this is it!

Yes, it's fungal. The spots don't have a distinctive "halo" so that rules out Early Blight. The first of the two photos I posted above shows Septoria Leaf Spot. Your spots look too big. The water-soaked look around the spots and the yellowing on the other side of the leaf suggests good old Leaf Mould to me.

Here's what it typically looks like, top of leaf and bottom:

Look familiar? There was a thread largely about it only the other day. It's about the most common fungal problem with greenhouse toms, in fact it's rarely if ever seen outdoors. Unfortunately, like all fungal problems, there's no treatment once it's established. All you can do is remove and destroy affected foliage. And wash your hands before touching healthy foliage.

Unless you spray preventively, your only defence against these problems in a greenhouse is as much ventilation as possible - a friend of mine used an electric fan on low speed to aid the air circulation - and keeping the foliage as dry as possible. But, as I say, it's very very very common.

One of the unfortunate ironies is that there's a school of thought that the PL varieties are less susceptible to fungal problems. Never believed it, myself.

The ultimate danger, obviously, is defoliating the plant. I'd even take the plant out of the greenhouse for a while if that's at all possible.