I thought Irish people are experts on growing potatoes. Just kidding. But on serious not ,as Dave mentioned, yellowing in most cases is a sign TOO MUCH watering and/or TOO LITTLE nitrogen. Also , I think potatoes need more "K". K is for roots. My potatoes are about 50Cm tall now and in a week or so they should flower. I have not fertilized them exept at the time of planting and water them maybe once a week or so. I have about 10 hills in one row. Also, potatoes should be fertilized from the bottom of hiil , close to the roots, not from the top. The hill is just a housing for the tubers.

Leaf curling alone is a physiological condition caused by stress; it's common in stressed plants, including young plants which don't have the root system to support all their foliage yet, or in times of unusually bright sunlight. If you get it by itself, look to see what may have stressed the plant recently; often it's nothing to worry about. The wilting, dead green leaves symptom resembles bacterial wilt, but that's pretty rare in your neck of the woods, and tends to take the whole plant down very rapidly. Stem borers can sometimes do it; look for little holes in the affected stems. Look for any damage to the stem, in fact. With the yellowing and necrosis -- it's hard to see in that small a photo, but it looks like the dark lesions are following the veins. That's diagnostic of a toxin of some kind -- no virus I know of does that in tomato, no bacterium or fungus is that specific, and no deficiency kills the veins before the interveinal spaces. I've seen a symptom almost identical to that in a case of alcohol poisoning (someone had a cocktail party in a library foyer and apparently the drinks weren't very good, as the potted plants looked pretty rough afterward). It was an unusual enough symptom that it became a teaching example. Toxins can come from outside or from the soil. Pyola is perfectly safe for tomatoes, and the heat wasn't excessive, but make sure the dilution was correct, as too high a concentration can burn leaves much like that. Spray damage can also cause wilted and dead green leaves. If you can sacrifice a plant that's badly affected, dig it up to look at the roots, see whether it has lots of crisp, white, fine roots, not dark or knobby ones. Shave away the skin at the soil line to look for discolorations in the woody stem underneath; cut open wilted green shoots to check for hollow centers from stem borers; and finally split open the main stem to see whether it's hollow or discolored inside. I don't expect much except maybe root symptoms, but you really never know. My personal guess is soil toxicity, especially given that the lower and terminal leaves are the worst affected by the yellowing and dying, and some things take a while to build up in the leaves enough to kill them. One important thing to note is that not all toxins are synthetic chemicals -- an excess of certain minerals or nutrients can poison a plant. pH affects root uptake of anything enormously, especially minerals, but it can have its own effect as well. You may need a soil test -- call your Agriculture Department, Cooperative Extension, or U of O to find an affordable lab. I don't see your symptoms in any of the common nutrient toxicity listings, though, which means it could be something chemical, and there is no general panel for that. Down here in California I'd send it to Sacramento's Plant Diagnostics lab or the extension pathologist at U. C. Davis, but I don't know what pathologists you have at your disposal. This is certainly not a cut-and-dried common disease problem, and even a specialist is going to need some lab work to figure it out, I suspect. I wish I had more answers for you, sorry. --Alison

That looks physiological to me, not pathogenic. There are a couple of possibilities, depending on what you do with your plants. Some nutrient deficiencies can look like that; magnesium, potassium, maybe molybdenum. If you haven't fed them recently, or if you have been feeding them a straight NPK food and your soil isn't the best, consider supplementing with a complete fertilizer or tonic, one which has trace minerals. (I'm fond of Superthrive for hard-to-pinpoint problems like this.) Low pH can also mimic nutrient deficiency. It could be fertilizer burn, though it's not perfectly typical. If you've been feeding them a lot, lay off for a bit and see whether it resolves. The last possibility I can think of is spray burn. Sulfur and some oils can burn foliage at high temperatures (over 85F) and even simple soap at high concentration can burn; it's common for the tips of the leaves to get higher concentrations of the spray as it runs off. You didn't mention any earlier sprays, but if you have done any, watch your temperatures and try to get an even spray without a lot of runoff. Don't mix different sprays together, either. I don't suspect a fungus because the yellowing pattern is so regular, and the dead patches are in the center of the yellow areas which speaks of it either being the center of the toxicity/deficiency, or being a victim of sunburn as the leaves get too pale to handle the sun. I hope some of that helps. :) --Alison

It's probably the heat. Cherries don't do well in the heat. It should start to get better by the end of September if you keep the tree consistently watered. If you really wanted to go out of your way to tend to the tree, you could mist the leaves during the middle of the day (sometime between 12:00 to 4:00 ). I've even heard some people have very lightly sprayed their trees with mineral oil, or lightly rubbed some petroleum jelly onto the leaves, to help keep them from drying out. It's the height of summer right now, and a little browning is to be expected. San Jose has clearer skies than San Francisco, so less protection from the sun. In short, what you are seeing is perfectly normal for the climate you are in. There's a reason most commercial cherry orchards are based in Michigan and Eastern Washington. Also, in San Jose (all the paved surfaces in the surrounding area has an effect on temperature) it's quite likely your kwanzan trees are not getting quite the degree of winter chill that they would prefer. This results in slightly reduced vigor, and that is also associated with browning of the leaf tips. Your tree should fair better in future years when the roots have become more established (and they can provide a more adequate water supply to the leaves).