This is a photo of a tomato plant from Southern California. Notice the yellowing leaves even on new growth, but the dark green veins. I'm thinking Magnesium deficiency. Your thoughts, please.

Consider also red spider mite,not easy to see check under leaves with a magnifying glass, but magnesium deficiency would be my first guess. Sudden temperature change can also cause yellowing.

Good suggestions Terry. And I'm thinking there are all those diseases to consider. Here's a page for you from the Texas Plant Disease Handbook that I have on our links page with lots of other good veggie research sites under my category for Texas Gardening and Resource Links

tomato diseases

Terry, that's exactly the way I started out my response to my cousin in So. CA who sent me the photo. I said, if this were a Texas tomato plant, my first thought would be spider mites. I explained to her what to look for just in case. Then proceeded with what to do for Mg deficiency, as well as reminding her to compost the base of the plant well, and gave her a recipe for a foliar feed that she can use on her whole garden as well.

Maggie, thanx for the link. I don't believe I've seen that one.

If this is magnesium deficiency, a dose of epsom salts will work wonders. We have not had spider mite problems in our part of TX but it never seems too early or late for them...usually when it is really hot and dry. Eva

... oh yeah, and Mr. Eva's tomatoes grow like trees too! They looked like decorative shrubs in the garden with big red shiny blooms, last time I was there. Let me know if ya need harvest-help Eva ;-)