It is hard to diagnose from a photo unless a person is a trained diagnostician or very-well experienced with disease on their own plants. To me, a photo shows only one specific point in time, and it is easier to diagnose what is going on with plants when you see them every day, you watch as it develops, and you know first-hand what every day of temperatures, wind, and rainfall has been like, particularly in terms of the way those things affect the emergence and development of discolored spots on leaves. Also, for any random gardener, you really can only diagnose what you are used to seeing. I never see Late Blight on my tomatoes or potatoes, so I find it harder than Early Blight to diagnose from a photo because I do see Early Blight to some extent most years and have experience with its appearance. Also, it is not unusual to have several things happening at once so that can make diagnosis difficult. Even letting potato plants get extremely dry can lead to foliar damage, so it is easier to diagnose when you know the whole day-to-day history of the conditions the plants have been exposed to.

I'm not sure if you're asking if it is Early Blight (Alternaria solani) or Late Blight (Phytopthera infestans). In our climate, Early Blight normally first appears in spring, but not usually this early in spring, especially since it has been a pretty cool spring. Even in a wet and humid year, I generally don't see it at all until very late May and often not until early to mid-June, and it is still April here, and a fairly cool April overall this year,

In the photos, since they were taken from a distance, we cannot see the brown lesions on the leaves well enough to tell if the concentric circles common with Early Blight are present within the brown patches. In the last photo, you can see a golden/yellow halo around one of the brown patches, and that is something you often see with Early Blight. So, look closely at your brown spots and see if you can see the concentric circles within the brown spots. I'm not seeing them, but that could be because of the distance the camera was from the leaves in question. Or it could be that my eyes are getting as old as the rest of me.

If it is Early Blight, there is no real cure, but this early in the season, you often can stop it from spreading by regularly spraying your tomato and potato plants with a preventive fungicide like chlorothalonil, which is found in products like Daconil. The label will recommend how often to spray. If you look at your leaves and decide it is Early Blight, remove and dispose of all the affected foliage and spray the plants with a fungicide. Merely removing the affected foliage doesn't put an end to the Early Blight which can be spread in several ways. Mulching the ground with a heavy layer of mulch can help reduce its spread. If you have Early Blight spores in/on your soil, every time it rains or you water, soil splash can carry the spores up from the soil and onto the plants so that is why mulching the soil is very important.

It doesn't look like Late Blight to me, and normally Late Blight is not an issue in Oklahoma, although it can crop up occasionally. Late Blight can survive on living plant tissue but not in soil, so you would have had to have an infection source from someplace (like, for example, a pile of cull potatoes that were infected with Late Blight and which somehow did not rot and disappear outdoors over the course of the winter), and Late Blight only appears under very specific temperature and moisture conditions in combination (that we usually don't have here for very long). The brown spots don't look enough like Late Blight that I'd consider it a likely candidate.

Lots of things cause brown spots like you have on our leaves, including environmental stress like very strong winds and even potato leafhopper damage.

Usually if I get freeze or frost damage on my potatoes or tomatoes, which is incredibly rare since I began using floating row cover/frost blankets, the damaged portions of the plants go limp and have that water-soaked look. I prune off the damage and the plants quickly regrow. If they get very mild frost damage there is some browning or blackening of the foliage and some limpness to the damaged leaves, but to be honest, I haven't had damage like that in several years and I am not sure I'd recognize it any more if it happened. When you haven't seen something in a few years, its appearance fades from your memory.

Covering potato and tomato plans with sheets is one of those things that might save the plants from damage if your temperature is dropping down close to freezing without actually hitting freezing or if you have only a very light and patchy frost, but there are absolutely no guarantees. It is one of those things that is better than doing nothing, but only marginally so. For reliable frost and freeze protection, you need to use a floating row cover that has been tested and rated to provide a certain degree of protection. The very first one I bought gave 6 to 8 degrees of protection and protected the plants from moderately heavy frost. I bought a larger amount of row cover that gives 2 to 4 degrees of protection and was disappointed. With it, the protection was poor and patchy---and leaned more toward 2 degrees than 4 degrees. Last year I bought a very heavyweight frost blanket type row cover that gives 10 degrees of protection, and have been thrilled with it. These row cover fabrics give plants better protection than you'll ever get from sheets. When I first started using actual row cover instead of my pile of old sheets and blankets, I couldn't believe how much better protection a good weight of row cover provides. If I'd known it would have worked so well and been such a useful garden helper, I would have bought row cover 15 or 20 years earlier than I did.

When you have a problem with some sort of leaf discoloration on potato and tomato plants, the TAMU Tomato Problem Solver is a great website to use to attempt to diagnose the issue yourself. There's photos and descriptions of the diseases common to this part of the country. Cornell University's Vegetable MD Online website is pretty helpful too.

If you aren't seeing whatever you have pictured on the leaves in the photos spreading and getting worse, I'd lean towards windburn or a little cold weather damage. Watch for the potato leaf hoppers, though. When they show up, they can damage potato foliage, in particular, very rapidly, but also can damage tomato foliage.

Here is a link that might be useful: TAMU Tomato Problem Solver

Okiedawn wrote "Last year I bought a very heavyweight frost blanket type row cover that gives 10 degrees of protection, and have been thrilled with it."

Could you please tell me the name brand of the row cover you are using now or a link. I was not happy with the cover I used this last winter and will be looking for something different this year. Also, I am still working full time and in the winter have to leave the house before full sunrise and don't get home until almost sunset. Can these row covers be left on during the day if the temps get below 32 overnight and about 60 F during the day. We get wild swings in weather here in Georgia between night and day.

Hi Yolos,

The kind I bought is made by DeWitt and I bought it from a company called Agricultural Solutions. They have it in all kinds of sizes. I bought a 250' roll of the 12' width so that, if a late frost or freeze threatened long after the tomato plants were getting tall and were caged, I could cover the plants without having to remove the cages.

This row cover is very heavy. When I take a 60' long x 12' wide piece down to the garden, the 200' trip seems like it is about a half-mile, so be careful not to be a piece wide enough to cover an entire garden with one piece.....it would be very heavy unless your garden is tiny.

I have left it on my plants during the day when the highs have gone into the 70s and maybe even into the low 80s and they were fine. It is not something I'd leave over a row of plants for more than a few days at a time because it does not allow much light transmission. I didn't buy it for light transmission, though, and never intended to leave it on 24/7 for more than a couple of days at a time.

Our weather is like yours in that it can fluctuate greatly some years. I think my greatest 48-hour fluctuation this year has been a 24 degree night followed one day later by a high temperature in the 80s. I've used lighter row cover, but with uneven results. I am in a cold microclimate in a creek hollow in a river valley, so if there is any place that is going to get really cold, really late, our property is the spot. I love, love, love my frost blanket row cover.

It has a fancy name I never can remember but I'll give it my best shot. At the link below look for a name that is something like Dewitt 3.0 Oz. Ultimate Frost Blanket Thermal Blanket or something similar.

I don't think they list what percentage of light gets through, but they might e-mail you that info if you ask.

Hope this helps.

Dawn

Here is a link that might be useful: Ultimate Frost Blanket Thermal Blanket Row Cover

Thank you so much, Dawn! I took another look - and some closer pictures. I don't see the rings you described as being a telltale sign of blight. Maybe this is just frost/wind damage and/or stress from the erratic weather. Have you see anything like this before? It doesn't seem to be spreading, and there are three tomato plants that are closest to the corner of the fence where it is more sheltered and they look much better and don't have any of this at all.

Shelley, Usually when my plant leaves have brown edges this early in the year, it is wind burn. We had wind gusts to 47 mph earlier this week and a lot of my plants got wind burn, but not my potatoes....they are at the lowest end of the garden, so the woodland to the north of the garden that sits only about 5' from the north garden fence protects them from strong north winds. The plants that got the strongest wind and most damage were greenhouse plants I'd moved outside as a continual part of the hardening-off process because they were on the highest elevation of our land where the wind is the worst.

The fact that it isn't spreading on your plants does make it sound more like environmental damage than disease.

Potato foliage gets all sorts of issues some years and none in other years. Generally, though, except in the wettest years we have here--like 2004, 2007 or 2010, I rarely see significant disease issues. I tend to look at the foliage, say "oh well" and go on about my business. I get the same size yield whether the leaves have looked good all year or have looked like crap. My potato yield is affected much more by how early we get insanely hot than by anything that shows up on the foliage.

I have a very hands-off approach to spots, specks and blotches on plant foliage---it happens and I ignore it. Worrying about it doesn't do any good, I'm not going to spray my plants with chemicals unless they are in imminent danger of dying (which is extremely rare), and we generally don't get enough moisture here in our area about 7 or 8 years out of 10 for anything of fungal nature to spread. In other words, I don't even care what the plant foliage looks like. I am not growing these plants for ornamental reasons---I am growing them to produce food and what I care about is that their energy is going into producing food, not that their energy is going into making pretty foliage. So, if I seem lackadaisical about foliar damage, it is because my plants produce just fine even with ugly foliage. With a big garden, I have to focus my energy on the big jobs like weeding, watering, mulching and harvesting. That doesn't leave me time for worrying about the foliage. About the only issue I'll spray for is Septoria Leaf Spot, which I see at a level that needs spraying about 1 year out of 8 or 10. It takes a whole lot of bad-looking leaves to get me to even look twice at them.

If you are the type of gardener who worries and frets over the issues that show up on leaves because it drives you nuts, you could/should spray your potato and tomato leaves with a fungicide that contains chlorothalonil regularly from early in their lives. These fungicides protect the foliage from becoming infected by fungal disease by coating the leaves as a sort of barrier. They don't work as well once the leaves already have issues.

I probably drive garden visitors crazy when they point to spots on a tomato or potato leaf and say "what's that" and I tell them what it is and they say "what do you do to control it" and I shrug and say "nothing--I'd rather not have chemicals in my garden". Too often, we gardeners think we have to do something to keep the plants looking perfect, but what I have learned is that plants that look significantly less than perfect produce about as well as plants that look perfect. We're in our 16th year here and I have sprayed my entire garden twice in one year, and otherwise haven't sprayed much at all. That one year I used Bt 'kurstaki' to spray in a year when the climbing cutworms and army worms were eating everything down to the ground a few years ago. They were so bad, you couldn't find Bt in any store within 50 miles of our house. I just kept looking for it and asking for it until a new shipment came in at a local feed store and we got some that first day before it sold out. My feeling is that my garden is an environment/habitat inhabited by us and by our animals and lots of wildlife, and I'd rather not spray anything in that environment if I can avoid it, and that includes organic products as well as those that are synthetic in nature. Some organic products are just as dangerous as the synthetic ones they are supposed to replace.

We have wind gusts up to 70 mph and hail in our severe thunderstorm watch currently in effect this morning. I sure do want the rain, but dread the rest of it all. I'd go out and cover up plants, but how the heck would I get anything to stay over them in 70 mph wind gusts?

This has been a more-challenging-than-usual spring, in terms of erratic weather beating up our plants, and it isn't over by a long shot. I spend a whole lot more time trying to protect plants from all the severe weather than from foliar disease because it is a much bigger threat to the actual harvest.

Dawn