Alaskan Yellow Cedar Foliage Issue

Arcto

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I’m putting this out here in hopes that members with a lot of experience with these can help out. I picked up this Alaskan Yellow cedar last winter. This mottled yellow coloration started appearing late this spring. It doesn’t appear to be spreading. Otherwise the tree has good color, is growing well and healthy. Anyone out there ever have a similar symptom to this?
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Hard to tell from a photo. Lots of things can cause the "leaves/scales" to yellow. Too much water. Lack of a specific nutrient (ie nitrogen) etc.
If it's just in one spot and the rest of the tree is fine, I'd cut it off to be safe.
 

Leo in N E Illinois

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If you can cut it off, that would be the safest, clean tools after making the cuts before moving on to the next tree.

Low probability, but it could be virus.

Higher probability, it could be a localized nutrient deficiency.

If no further reoccurrence, then it doesn't matter what it was.
 

Arcto

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This was a collected tree from V. IL. It was also fully green last season. Checking thru my trees, I found this affected Shimpaku branch showing similar symptoms. Those I cut out.
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I’ll probably remove as much as I can do without excessively weakening the tree as it is scattered throughout.
 

Leo in N E Illinois

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I've seen this, in orchid seedlings. One leaf of a sympodial orchid will come out partially bleached, yellow or white. Almost always happens in a very rapidly growing seedling, and only happens on one or two individuals. The speculation, without proof, in the orchid circles is that the individual plant had a "growth spurt" and outstripped its own vascular system's ability to supply nutrients to that zone, resulting in bleaching. The bleaching almost never reoccurs. This is wild ass speculation, by people with advanced degrees in fields other than plant physiology. (a poke at a friend who is an advanced nuclear physics PhD, doing very high energy laser research, at Argonne, who was speculating on the phenomena, with me one day).

Alternately, it could be a local epigenetic change, causing a local zone of variegation. Again mere speculation. But a non-pathogenic cause for the color change.

Finally, one symptom of plant virus is color break, streaks of color, often accompanied with small streaks or spots of necrotic tissue. Your tree looks too healthy for this to be virus. But, it is difficult to tell just from a photo. The occasional streaks of necrosis in addition to the color changes are key to the "Virus Guess". If you have no necrosis, you probably do not have virus, but only a test can confirm. There are test kits available, suitable to use in a farm field (reagents in bag, basically stick a leaf sample into a bad, add tiny amount of very fine pumice & macerate leaf with fingers, then add the reagents, dip in test strip to the macerated goo, wait for color change). But each test kit is specific for a single virus, there are hundreds of identified plant viruses, I have no clue which one you could possibly have. Also you can't buy just one kit, need to buy in lots of 25 or more, and at $5 per individual test it adds up.

There is no cure for virus, tools should always be sterilized after touching a suspect tree. 70% isopropyl alcohol wipe down will kill virus on tools. TSP soap solution will clean virus off tools. Heat from a flame will also work, but flaming will destroy temper of cutting edges. If bonsai growers were smart, tools should be wiped down with alcohol every time you move from one tree to another.

When investigators look for plant viruses, they are found, unique viruses have been found for just about every group of plants tested. The isolation of viruses is expensive, so the search is largely limited to economic crops, and pretty much without exception, if you look for plant viruses, you find them. But the number of plants tested compared to number of species world wide is quite low. So it would be wise if as bonsai growers we stay aware that a common vector for plant viruses are the cutting tools that are not cleaned as the horticulturist (or farmer) moves from one plant to another. Other vectors include insects that suck plant juices. Nematodes, and a few other vectors not coming to mind.

So honestly, I have nothing but speculation to offer.
 
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