Disease starting at the top of the plant

[Mark0820]

The only real disease (on tomatoes) that I have had to deal with is early blight, so I am used to seeing the disease start at the bottom of the plant and spread upwards.

This year, I have early blight, as usual, but also have a new disease (or possibly insect damage) that is starting at the top of the plant. The leaves have light brown spots (almost tan) that appear to grow larger with time. There is also a very light yellow color (yellowish / green) around the brown spot. The brown spot is sort of crunchy, but not to the point that it breaks apart when I touch it. I can touch it, and none of the brown spot crumbles. I sprayed the plants with Otho Max disease control on Monday, but this new disease has been spreading at a fairly good pace.

I have looked on Cornell's site for tomato diseases, and cannot find anything that resembles what I have. I have also looked through this forum, and cannot find a thread that addresses this disease.

Does anyone have a clue as to what it might be?

[Mark0820]

I just found something that looks somewhat similar: drought stress. The pictures of drought stress appear to have more yellow on the leaves than what I am seeing on my plants. It is really hard to tell from a photo because the colors can be distorted. I'm not sure if this is what I have, but it appears to be a possibility (we just had 14 consecutive days of 90 - 100 degree temps).

http://www.longislandhort.cornell.ed...ght_stress.htm

I'm still interested in other ideas because I am not certain this is what I have.

[RayR]

The picture at Cornell is a good representation of what drought stress looks like, but the amount of yellowing varies at first. Those leaves and stems will eventually dry up and fall off. It's easy to mistake it for early blight at first if you've never seen it before.
I've seen drought stress on lower leaves of some of my in -ground plants because of the lack of rain here, so I stepped up the watering.

Mark, do you have any pictures of those spots on the upper leaves of your plants?

[Mark0820]

Ray,

I don't have a picture. What I am seeing on my plants looks a lot like the very last picture on Cornell's drought stress article. I'm not seeing any small round brown spots like some of the pictures show. My leaves have larger patches of brown spots, and they don't have as much yellow showing either. I just have a very light yellow color.

I am seeing it at the Community garden, and I did notice the plot next to mine has it worse than I do (I am downwind from them). It is only touching the tops of their plants also, but it looks like it is just getting started (whatever it is).

I first noticed it on my Couilles de Taureau plant. It looked like it was spreading fairly quickly, so I removed the plant to be safe (since I haven't been able to identify what it is). The leaves on the Couilles was touching my Red Barn plant, and I have seen a few spots on that plant. At this point, those are the only two plants I have seen it on. I am hoping to identify what it is before I sacrifice the Red Barn plant.

The Cornell site said drought stress is often confused with late blight. I have looked at pictures of late blight, and it doesn't seem to quite match what I have. In addition, I have never experienced late blight in my area. I have also looked at pictures of grey mold, but that has more of a greyish color to it than I am seeing on my plants.

[ca1ore]

I must say, there are a few things that seem to mimic blight (either early or late) for the casual gardener. I've had leaf symptoms this year that the pessimist in me was convinced was late blight - but the local testing lab found no evidance of fungus of any kind. His view was that the symptoms were physiological - either too much or not enough water or not enough sunlight due to lots of cloudy weather. I also have a few plants that looked suspisiously like they had CMV, yet most of them have resumed producing normal leaves. My only issue right now is that some of my plants are massive (a few over 9 feet tall) without a tomato in sight.

[Mark0820]

I took some leaves to the county extension office, so I hope the OSU person will be able to identify the problem.

It did occur to me that pulling the plant wasn't the smartest thing to do. This is my first year in a community garden, and I wasn't thinking about the fact that disease control is only as good as all of the participants in the garden. Since the garden next to mine has the same thing, I'm not gaining anything by pulling my plants unless they pull their plants.

I also noticed the garden next to mine has some leaves at the bottom of the plant with this problem, but more at the top of the plant. However, there didn't appear to be any pattern to the diseased leaves, so maybe it is just stress or something non-threatening. Therefore, I am guessing I have this problem at the bottom of my plants, but just can't see it because I also have early blight on the bottom leaves.

[Mark0820]

The OSU contact at the county extension office said he thinks it is just a continuation of the early blight I have at the bottom of the plant. He said it could be drought stress, but it looked more like early blight to him.

I mentioned that in the past, the blight I have had always started at the bottom of the plant and moved up the plant. He said that is more common, but also said early blight can jump from the bottom of the plant to the top of the plant.

[Mark0820]

The one thing I learned most from my early blight experience this year is to never feel safe. In past years, early blight has always shown up in April / May. Therefore, I knew I was going to spray from the plant out date. This year, there was no sign of early blight in May. I thought that since we had a warm Spring, maybe there wouldn't be any early blight this year and I wouldn't have to spray.

However, I got caught off guard. This year, early blight arrived in mid to late June and I wasn't prepared. Going forward, I think I will be using some type of spraying program from the day I plant my tomato plants in the garden. If I would have done that this year, my plants would be in much better condition.

[RayR]

Originally Posted by Mark0820

The OSU contact at the county extension office said he thinks it is just a continuation of the early blight I have at the bottom of the plant. He said it could be drought stress, but it looked more like early blight to him.

I mentioned that in the past, the blight I have had always started at the bottom of the plant and moved up the plant. He said that is more common, but also said early blight can jump from the bottom of the plant to the top of the plant.

Your OSU contact is correct in that Early Bight can jump from the bottom foliage to the top. There was a study done by German scientists in Cuba about 8 years ago on Early Blight and their findings proved that the leaves most susceptible to Early Blight infection were the oldest leaves, followed by the youngest leaves.

[Mark0820]

Thanks Ray! Interesting study.