Snek, the symptoms you describe here and in the other thread match my experience so far. Only affecting the Meyer lemon (and mine is in the ground on standard rootstock) and not spreading to any adjacent trees.

I did recently find a contact in the CDFA Plant Pathology office that offered to diagnose, so I'll probably send a cutting in soon and perhaps we can all resolve!

I see ACP all the time (even today, in the winter) on the citrus in Westchester. If I look daily, I see them daily. 100% certain of ID, they're just under the size of the exclamation mark "!" on a standard keyboard and in the conventional head-down-diagonal feeding position. Neighbors who have used imidacloprid products haven't seen a significant reduction in population.

What worries me is that they don't stop at just the newer/younger growth, but also have been attacking the hardened leaves (and once, even saw one trying to feed on a thorn). Year-round concern.

But the hope is that they aren't (currently) carrying HLB.

Millet, thanks. I did catch that in the other thread. Looks like it has Neem extract too. Heavy duty combo with the pyreth. and soaps - probably takes out the beneficials too. I wonder what it's defeating for the improvement?

People have seemed to think this is a form of greasy spot fungus.

To be honest, I tried another forum a month or so ago but am looking for more opinions. There was a long-ago post where another user (in Florida) had the same issue but never indicated if it was resolved (not sure if we can link there, but if you web search for "Problem With Meyer Lemon Leaves" and "charles27gardener" his post will show up).

My improved Meyer lemon (on a standard non-dwarfing rootstock) has been growing like gangbusters since planting a year ago. Recently, the underside of many of the leaves have started to become covered with rough brown spots. A number of the leaves fall off.

This is the only tree experiencing the issue of five trees that are about the same size and on the same watering schedule (two blood orange, one minneola tangelo, one page mandarin, and this meyer lemon).

The suggestion was fungal and that fungicide could control - I've begun that regimen but it continues to get worse (more leaves falling off, at the same time the tree is flushing with newer growth). Could it be mites? Edema? Fungal but takes longer to control? Other ideas?

I'm in the coastal Los Angeles area. Theoretically greasy spot is rare here?

Top of leaves, backlit (no noticeable issues with tops of leaves, but you can see where whatever is happening is affecting the tissue to make it lighter yellow) (Click for full-size)


Underside of leaves, note (necrotic?) brown spots (Click for full-size)


Fallen leaf top and bottom (click for full-size)


The tree itself, in lighting that doesn't reveal the issue, except for the defoliation near the top: