[MikeHardman]

My little kumquat (1.2m tall) was doing very well, apart from attack by citrus leaf miner, for which I sprayed with a systemic insecticide some while ago. Later, it started bearing a good crop of flowers.

More recently, the leaves have started falling off, while still green. They first develop a central brown blotch, and they are not fully withered when they drop off. I can find plenty of web sites that show all sorts of leaf problems, but none match these symptoms. The remaining leaves seem to be more firmly attached, and do not have the brown blotch. ...So it is the older leaves that are most-affected. In principle, this sounds a bit like normal shedding of the old leaves, except: the brown blotch, no sign of the usual yellowing preceding leaf-fall, happening all of a sudden, and all the flowers and fruitlets have dropped off, too.

I wonder if it is my fault. Most of the irrigation goes down a 50mm pipe straight to the roots, but I recently increased irrigation, including at the surface. The base of the trunk has been getting wet, and has been exposed to the hot sun. I'm afraid I may have cooked the wet base of the trunk...

Yesterday, I ceased surface watering, and  I built a little cairn around the base of the trunk (close, but not touching), to keep the sun off (see photo).

I would appreciate any opinions on:
- identification
- treatment
- significance for adjacent Citrus, Prunus and olive trees

Regards,
Mike

[David Bracey]

Pic 2 looks like your kumquat is suffering from lack of N but maybe its the sun since pic 4 looks ok.  Could it be sunburn?

[pamela]

Not a happy bunny that Kumquat!.    For what its worth I think that your environment is not right.  Kumquats don’t like wet feet but as well I am seeing an irrigation system far too close to the trunk. That irrigation only looks after a few inches around the plant the feeder roots will branch out and then they are going in to seriously dry stony soil.  The plant is far too small to tolerate that.  It would be much better in a pot where you can manage a slightly damp condition of soil for it.    In Spain as you know citrus grow well but they are not endemic and always have to be on an irrigation system.   Those systems are very carefully placed under very 'voluptuous' bushes, which give a wide shady area below to protect the dampness of the soil. I don’t want to be negative but I think sadly for you it might be wrong plant in wrong place in this case.

[Caroline]

Although it may seem very drastic, you might also want to consider cutting the kumquat back hard. My experience (two kumquats in pots) is that they respond well to this, so that if you can get the watering right, a hair cut might encourage it to shoot again.

[MikeHardman]

Thanks for your comments.

David:
I don't think it is sunburn. The other sunburn I have seen is distinctly yellower and the patches fade more gradually into the normal green tissue towards the edge of the leaves. Also, it seems very sudden. Lack of N is unlikely - it had a balanced feed in Jan-Feb. And if anything, it might be N-toxicity - since I put a pinch of high-N granules into the deep-watering tube.

Pamela:
The dripper was still there from when the tree was much smaller. It had been turned-off for over a year, but when the tree was looking a bit wilty, I opened it again - but without thinking to check on the wetting of the trunk base. The dripper is out of the way now. So it is back to being irrigated by a 50mm pipe going down about 30cm, with perforations in the lower half. It was doing OK on that until recently, when a drop in water pressure (below my already low 2bar) caused some of my irrigation to stop working (hence the tree becoming wilty).
I havent' done it on the kumquat yet, but on my other fruit trees, I have spread Aptenia prunings around the base to cool and mulch the soil, and shade the base of the trunk. I shall do that for the kumquat as well.
I have grown other kumquats in big pots, but found them prone to ant nesting - making them just too quickly-draining. hence my planting this one in the ground. It was doing OK until recently; last year it make good growth and gave a good crop of fruit. But I take on-board your cultural comments. I think I will adjust the irrigation moat so that the trunk is on an island, and the moat itself extends further away. For the time being, Aptenia prunings will have to suffice in lieu of 'voluptuous bushes'.

Caroline:
I am willing to hard-prune, but only as a last resort. For the time being, I shall be keeping a close eye on the tree, looking for signs of twig bark shinkage (pressagng death), cessation of leaf drop, new shoots, etc.

Thanks again.