Just adding another photo of the spots

Different diseases appear in different parts of the country so could you please share with us in a geographic sense where you grow your tomatoes.

Are there any other tomatoplants you grew, or only this one and did you grow it from seed or buy it and if others do they all, or most, have the same symptoms?

What has the weather been like lately where you are.

Is it a new place where you are growing, and I ask b'c you said the leaves were turning yellow from the bottom up.

Carolyn

johannajo, did you mulch ?

Did you fungicide ?

This post was edited by Daniel_NY on Wed, Sep 10, 14 at 22:08

Thank you for responding! I live in Portland Oregon. I got the plant as a seed late this spring. It's my only tomato plant, and I keep it on a pot on my balcony. ((Recently my basil plant that is also on the balcony got downy mildew and I relocated it and started spraying it with a mix of baking soda and dr bronners and resolved itself. I don't know if that would affect anything)) I haven't used mulch and I haven't used fungicide. And the potting mix I used is some general "organic fertilizer " that I've used with all my plants.

Oops, I forgot to answer all the questions! Also, the weather has been pretty hot but cold nights. It's also been pretty windy, the plant got knocked off the balcony in a windstorm a week ago and lost a branch. And I've been growing them in the same place all summer.

I your case could be Gray Leaf Spot.

One of the most common methods of tomato leaf infection is through rain splashing on bare soil. During a rainstorm, water droplets hit the soil surface, splashing water and soil up onto the lowest tomato leaves. Prevent rain splash in your garden by covering the soil with mulch.

Source: Controlling Tomato Leaf Spot Diseases

A mulch that I recommend: Landscaping Fabric (Dewitt).

This post was edited by Daniel_NY on Wed, Sep 10, 14 at 22:10

Have you used any fertilizer? If so, what kind and when?

Can you post a picture of the whole plan?
How big is the pot? what kind of potting soil you have used? How often do you fertilize it ?
Is the leaf shown is from the lower part ?

It is possible that your plant needs more nutrients. All I can see is that it is yellow (lack of nitrogen).

Potted plants need more frequent almost continuous feeding with water soluble fertilizer at 1/4 to 1/3 recommended strength.

Also, cool temperature can cause pale color, together with less direct sun. I also live in your area (Seattle, WA). we get cool nights ALL the time. Tonight it is going to dip to 49F. Today's high was 73F.

The other option is fo spray with some kind of fungicide (Daconil, Neem Oil, etc). I would also trim all and any severly yellowing leaves, as they no longer make a contribution and might harbor diseases.

It's pointless to spray when disease isn't preset.

We still don't know anything about fertilizer.
Was it used?
And if so, when and how much?

If only watered, even if the potting mix already contains fertilizer, it needs supplemental fertilizer.

It's pointless to spray when disease isn't preset.

%%%%%%%%%%
It is a common practice to spray tomato plants regularly, from early on , with anti fungal and anti bacterial, as a preventive measure. Often it is too late to try spraying when the plant is full infected. Most tomato plant diseases are fungal/bacterial.

So it is an option:, to prevent or to fight the disease.