6

What could be the reason to cause this discoloration of the leaves? The discolored parts you see here get thicker over the time until the green color disappears. It does not seem that the leaves dry out as the right one on the photo feels quite wet.

image of the leaf

  • have you looked on the underside of the leaves for insects or traces of them? – kevinsky Apr 4 '13 at 10:37
  • Your profile says you live in Leeds in the UK. If that's accurate, then I'm assuming this plant is not currently growing outdoors? If its outside it'd be some sort of miracle, and this would definitely be cold damage - is it in a pot in a greenhouse or in the house? – Bamboo Apr 4 '13 at 13:31
  • @Bamboo indoors (in the house). It's growing right in front of the window on the south side, so it should be getting full sunlight (though the last month was quite cloudy). – Andrey Cizov Apr 4 '13 at 19:21
  • @kevinsky I do notice them sometimes but I have bought sticky traps for them (insects being small flies). They have also started eating a couple of leaves, but these particular leaves are still alive and don't seem to be getting worse. Could they plant something inside the leaves? – Andrey Cizov Apr 4 '13 at 19:23
  • Andrey, what was it after all? I have the same problem and have difficult time figuring out the cause from this thread. Many assumptions but no definite answer. – lecamarade May 16 '15 at 13:32
2

This is caused by excessive drying. I have seen this happen when Morning Glory vines found their way into a house and grew up to the window. Even though the temperature didn't go under 65 degrees Fahrenheit (it was summer), every leaf inside the building developed the dead areas on the leaves, but outside they were fine. I thought it was a humidity issue, but discovered a few red spider mites on the plants. The drying effect of the mites plus the low humidity (they usually come together), causes the dry dead patches to form.

Note: The pictures below are of cold damage, not excessive drying.

Cold damage on morning glories comes as a blackening leaf collapse. See the pictures below.

enter image description here enter image description here

4

You've said its on a windowsill which has full sun exposure (if there's any sun at all that is). Can I ask if there's a radiator beneath the window, which is currently hot during the day? Do you have double glazing? Do you draw the curtains at night, leaving the plant between the curtains and the window? What size pot is the plant in and how long has it been in that pot, and how tall is the plant currently? It's just this still looks like cold damage to me - if the plant is in a heated room during the day, and is exposed to sun, then it's in very warm conditions indeed. But overnight, when the heating is off, and it's dark, and particularly if its on a windowsill with curtains drawn, that's a very cold place to be indeed, even with double glazed windows, and our temperatures are unusually low in the UK for this time of year.

  • I have had that idea before, but the leaves I have cut are not the ones to be nearest to the window, though they are one of the largest so it might be that the have enough area to be affected by the cold. Last month was quite cold as well, so it might be it. It's getting warmer though, so will report later :) – Andrey Cizov Apr 5 '13 at 13:31
  • It does seem like a cold to me as the cold days are now over in the UK and as I have decided to open my window less frequently (the leaves which were affected remain as they were, but it doesn't spread, so I keep myself calm about it). – Andrey Cizov Apr 15 '13 at 10:16
3

In my opinion, it could be a too calcareous soil, that causes chlorosis (leaves become white, then dry, then the plant dies)

Try to give to it some Sequestrene iron chelate. Very important to any type of plants, included cacti.

  • I will try this and report back in a couple of weeks. – Andrey Cizov Apr 4 '13 at 20:04
  • The chelate should be used only in the case of chlorosis (yellowing of leaves, the veins remain green), that occurs more easily in alkaline soils and potted plants watered with very hard water (calcium and magnesium, ie limestone). The chelated iron is in a form that is immediately ready for the plants. Being photosensitive, is better to distribute at the sunset. This is also true for chelates to give through the leaves. The first results will be visible in a short time. But now you need to change forthwith the water in the watering. Stop to sink water. – violadaprile Apr 5 '13 at 0:22
  • If the diagnosis is correct, measure also using manure to fertilize acidophilic plants. Following you need to work hard to change the ph of the soil. - Or just change soil. – violadaprile Apr 5 '13 at 0:27
  • In addition. Exposure to bright light and direct sunlight will accelerate the metabolism of plants. For potted plants, if the fertilization is not sufficient in relation to light, increases the risk of chlorosis. It is therefore necessary to increase the fertilizer and iron intake. You have to check the trio = light -> fertilizer / iron -> alkalinity of the water, and find the right balance. – violadaprile Apr 5 '13 at 0:52
  • I have ordered pH meters for the soil yesterday, should receive them in a couple of days and will report back. Though the leaves started to loose colour before we had any sunny days at all. – Andrey Cizov Apr 5 '13 at 13:34
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We don't have enough information to provide a definitive diagnosis. Close up pictures would help. Here are some possibilities:

  • thrip are common in greenhouses and indoor plants. The adults are the size and shape of an explanation point ! They have wings and can spread from plant to plant. They do the usual insect thing and suck juices from leaves. But the kids..they do damage typical of what is seen in the photos because they live inside the leaf and tunnel through the tissue. The adults leave black spots called "frass" on the underside of the leaf. You should see frass, and if you do not disturb the leaf, you might see adults. I have never managed to cure any plant of thrip even when I used systemic insecticides. They are too hard to eradicate and the plant should be destroyed.
  • some kind of virus is a possibility but ipomoae are not known for this. I could only find one reference for the sweet potato which is in the same family, and would not normally be susceptible unless the plant is weakened and there is source for the virus nearby

So, check for evidence and put up more photos please!

  • I have had some flies around but they didn't look like thrip. Though I could use a magnifier to look at them more closely as I am not sure what kind of flies these were. Do they always leave frass like on this picture? link As I have not noticed any in my case. I will put up more photos this evening. – Andrey Cizov Apr 5 '13 at 13:40
  • A severe infestation of thrip will always have frass on the underside of the leaves. The damage from the kids looks like silvery trails inside the leaf. – kevinsky Apr 5 '13 at 15:06
  • It does not seem to show any signs of frass under the leaves (mostly small black dots of dirt which look completely unsystematic, also I have not seen any of these on the affected leaves) – Andrey Cizov Apr 15 '13 at 10:11
2

I have similar problem with my chili plant. Its seems like a fungus problem in the soil if other leaves are also getting the spots. Change the soil entirely and check for root roth.

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