I'm far from an expert on tomato diseases, but what you show here does not look like a disease. It looks more like a water issue / nutrient deficiency to me. Possibly a lack of nitrogen or too much water.

Since it appears to be affecting the lower leaves and is moving up the plant, I would suspect nitrogen deficiency as a first and most likely suspect (assuming watering has been appropriately limited).

The first thing I thought of was Fusarium, but you didn't mention any wilting...

Late Blight the yellowing would be similar patterns but brown or olive green, and white mold on the undersides, plus brown spots/splotches on the stems.

Early blight usually has much more spots surrounded by yellow.

Many would only wish that their plants looked as good as yours. If you'd like, use a fungicide as they were meant--as a preventative, not a cure. This would extend the plant's life and is generally a good preventative measure to do regularly anyways, but let's see if anybody else chimes in.

what worries me is the speed of the change. 6 days ago I gave a daconil spray and removed the leaves which had yellowed and turned brown in spots... what you see in this picture was green when I did that.

its been 16 days since a 15-15-15 MG feeding, with one other watering and one generous rainfall in that span. sunny, afternoon temps in the 80s.

Are you trying to set a record for least amount of water allowed a plant?

For big, luscious tomatoes, I water DAILY (2x) with drip fertigation.

korney19 -

I am in Middle Tennessee which gets hot (afternoons often in 90s). With my tomatoes mulched with about 3/4 inch of cypress, they usually need watering every other day at most. And I just use the spray from the hose. I've got some nice big, luscious tomatoes ripening right now. Are you in a very dry area? Seems like 2x daily drip watering would be a little too much watering in my opinion. Just my thoughts...if you get good results, I guess I can't argue that you're overwatering.

Hmm.. well that's roughly 5 days per deep watering (with one due tomorrow), there's never been any sign of afternoon wilt, I check the moisture beneath the mulch daily and its never dried out; and the first fruit that's developed near full size shows no signs of BER.... so I assumed my watering was sufficient. temps here have been mostly in the low 80s for highs, very much below typical July temps.

Ken

Just so you don't worry yourself to death, all tomato plants eventually get yellowing leaves, even healthy ones. Nobody ever shows pictures of perfectly healthy tomato plants with yellow or dessicated leaves at the bottom. "Healthy" plants are always shown in pictures with perfectly green leaves everywhere. I think that confuses the heck out of people.

Notice the posted pictures of long time tomato growers here. Many may show yellowing leaves at the bottom or have signs of common diseases that the grower is dealing with, and the plants are producing quite well anyway.

Diseases usually come with spots, specks, or blotches that may or may not have some yellow in or around them, but I wouldn't worry about your yellow leaves. Just gently remove them since they aren't contributing to your plant's production any more and to prevent the attention of insects.

You're doing the right thing by being aware of what your plants are doing, but they look okay to me. Watering and fertilization issues are easily addressed.

Late blight does not appear with yellowing. See below pics. Those plants look fine. A "course of action"??? Yeah, stop worrying and be thankful you are not in the northeast.

I know I mentioned this earlier, but this really doesn't look like any type of blight or wilt to me. There are no lesions at all on the leaves pictured on the original post, just yellowing. No browned or burnt margins, no wilt, no legions. Just looks like either a nutrient deficiency or just plain old leaves.

As the pictures jtcm05 posted show above, if it were late blight you'd see the necrotic regions on leaves and stems and possibly no yellowing at all. If it were early blight you'd see small dark round lesions with yellowing concentrated around said lesions. If it were a wilt, you'd see, well... wilting.

My cherry tomato has leaves that look exactly like that. In my case, it was probably caused by not enough water and plant crowding. I put two cherry tomatoes in one 18 inch container, which was completely insane. The problem got particularly bad when I went on vacation and the neighbor didn't water them nearly enough.

With daily watering, the plants are still setting fruit like crazy, and the new growth looks fine.

Ken,

Your issue is very minor. The affected plants are drawing a bit of nitrogen off lower leaves to feed new growth. This takes on variations of appearance variety by variety, but generally looks like what you picture ... some yellowing of the more mature leaves.

You could give your plants a good side dressing of 10-10-10 or 12-12-12 or 9-12-12, etc. Or you could feed them again with Miracle-Gro or Scotts or fish emulsion. Whatever. Or you could just not worry about it. But a little nitrogen wouldn't hurt especially after a good fruit set.

With regard to watering ... tomatoes generally need a good deep soaking, preferably by natural rainfall, once per week. The equivilent of one to 1.5 inches rainfall is about all they need. This is for tomato vines grown in native soil or raised beds.

Tomato vines grown in containers or grow bags need much more frequent irrigation and feeding such as was mentioned above by a grower who indeed grows his in containers and fertigates daily. But drip systems are expensive and babying tomato plants is too time consuming unless you happen to be in the business anyway, retired, or unemployed.

I have yet this year to water any of my three dozen plants growing in raised beds or grade level native soil. It's rained enough to keep them plush. Last year I only watered the ones that showed leaf droop and only when the leaf droop indicated the need to water. The year (2007) before I had to water heavily in August and September because we were in a severe drought. Personally, I find "dry farming" tomatoes in raised beds heavily mulched is perferable to irrigating. But I live in a temperate area where I can expect a half inch or so of rain most weeks.

And with containers I find it better to discover those varieties that are hardy enough to weather it with a good 10-count or 15-count out the end of a garden hose once every other day and a gallon of half strength Miracle-Gro solution every 10 days or so. Indian Stripe, Bradley, Traveler, Creole and Cherokee Red are examples of such hardy cultivars that will do well with minimal irrigation in 10-gallon tubs. Golden Cherokee is showing the same ability this year so far.

I'm currently growing hybrids in containers, and despite having done everything wrong in the book, they are doing very well. They are growing in top soil, top dressed with potting mix. Most of it is dumb luck - I've fertilized twice, I water every day unless we get a good rain, and they are all approaching 5 feet with nice fruit set.

I rent, so while my landlord doesn't mind if I garden, he probably would rather I not dig up most of the back yard to do a full grown tomato garden. So I have four plants in old flower beds, and 6 in containers.

I should also add, that I'm a total newbie, and will use potting mix next year. And proper supports. And maybe try out a heirloom. :)

pennyrile, drip systems are more affordable than ever. You can buy kits under $10 without a water timer and as low as about $35-$40 with a battery operated timer and enough fittings to do 20 plants. Of course, an advantage is you DON'T need to be there once it's set up!

thanks everyone, I will continue as I am and hope for the best. the other plants all look tremendous, this one just got me scared as none of the others have issues in the mid-growth but this one. The leaves do turn necrotic if left a bit longer, but I had trimmed all of them a few days prior to the photo and these newly affected leaves hadn't progressed that far yet.