We have a satsuma mandarin about 12 years old that has been healthy until now. Leaves are turning yellow and falling off. The tree was recently given citrus fertilizer via spray and in the ground with watering. It does not have any visible bugs. Prior to its illness it did have black soot (this has been an ongoing issue), which was treated and we had a good harvest of fruit. There is no visible soot now. The soil has the proper moisture and a quick dig did not reveal root rot. We trimmed the tree. There are no flowers when they should be visible. I’m at a loss. Any ideas? Thanks
I don’t know if I’d be able to identify the cause, but pictures might help give a better visual what’s going on.
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@Stanthecitrusman and @Johnsgard, y’all are the first two to come to mind who could hopefully offer a clue on the issue that RPH52 is having with an established Satsuma mandarin tree.
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The yellow leaves suggest long-term and significant undernourishment (especially nitrogen, but probably also micronutrients, like iron, magnesium, etc.). Foliar sprays are most effective on new leaf growth, with minimal/no uptake by old leaves. Soil drenches with diluted fertilizer solution (50% normal strength MiracleGro or similar) should help re-green the foliage. Black soot implies infestation by a sucking insect (scale, aphids, whiteflies, psyllids, etc.). Controlling the invertebrate pest will eliminate the cause of the sooty mold. Not sure what “treatment” was used. Not sure where this plant is located, but it should have had its best yearly growth flush in early spring (typically March for Satsuma in southern U.S.), but looks to me like it failed to do so. Unless it was substantially over-produced last year, it looks like chronic undernourishment and possibly under-watering. Citrus leaves should always be dark green. Anything else indicates a problem.
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Citrus that struggle to make good growth and droopy foliage is often due to citrus mite infestation, but these leave behind silver-looking leaves and I don’t see those in the single photo included. They are often a problem in dry winter air. A magnifying glass is needed to see them. Diluted dormant oil or Neem oil emulsions are a good organic option for treating mites, but this requires complete soaking of the canopy, sometimes repeatedly.
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I applied another round of fertilizer and watered some more. I have also cleared out all the dead branches and leaves. We had “normal” rainfall this winter, 12.5 inches. The two winters before that were great for rainfall, 21 and 18.
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Let me know if it fails to respond to your latest treatments.
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The branches you had pictured looked pretty dark. If you cut a tree and expose branches to the sun, they will sunburn. It could just kill some of the branch or the whole scion. The rootstock will most likely survive. Just what comes to my mind from the pics and the conditions you said in your post.
I did a Rapitest soil test and got a strong blue color for pH, high alkalinity. That makes sense given the yellow leaves. Should I try sulfur treatment? The tree is a little better since I treated it with Miracle Gro All Purpose Plant Food and watered. I’ve got blueberries in a different location and they’ve never done great. I know they need acidic soil and have used amendments to boost acidity. The mediocre results with blueberries confirms this test showing that our soil is alkaline. Thanks
After 12 years the pH is now an issue? I am in Southern CA and our soil and water are higher on the pH side. I do nothing for pH on my citrus. I would look for other issues first. This is only an opinion.
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For plants that are under year-round irrigation, it is the pH of the irrigation water that sets the pH of the soil. Applying sulfur is only a temporary fix. If you apply it periodically you’ll send the plant on a pH rollercoaster ride – which it won’t appreciate.
Check the pH of your water supply. If it’s below 8, I wouldn’t worry about it. Common citrus rootstocks generally tolerate pH between 6 and 8. If it’s over 8, then consider fertigation with N-phuric.
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Sadly, the tree died. I’m still mystified as to the reason. I dug it up and the roots looked fine. All the leaves came off and then all the branches turned from green to brown. It goes back to a severe case of black soot. I treated it with horticultural oil and neem oil, but maybe I needed to use a fungicide with copper.