Meyer lemon - brown patches on leaves

I gently root-pruned my Meyer Lemon early last spring and it was very healthy when I brought it in this winter but it started new growth in November and had almost too many blossoms. I feed it a regular citrus fertilizer as recommended on the package, and give it an occasional side dressing of worm castings. The new growth seems to have stopped and now it is losing some leaves. The room has sun and humidity. The leaves look as shown, the left leaf is the way it starts on the plant - the right leaf is after it falls off the plant. I will remove some of the blossoms so that the leaves might get more nutrition, but can anyone tell me what is the cause of the patches? The tree is about 30 years old and about 3 feet high in the pot and has produced beautiful lemons. I watch for scale and other insects but that does not seem to be the problem.

This message was edited Feb 10, 2008 1:52 PM

Mygardens, you mention "gently" root pruning the tree. Did you "gently" top prune as well? If you didn't, this could be part of the problem. It doesn't always occur right away.

Have you checked the underside of the leaves with a magnifying lens? Some pests are very small and difficult to see with the naked eye. The leaf on the left side, as well as some of the leaves un the background look curled, an indication of damage by sucking insects such as aphids and mites.

How often do you water? Citrus prefer moist, but well drained soil. You may want to invest in a cheap pH meter. Very high or very low soil pH will interfere with nutrient absorption. Every so often you need to leach old salts out of the soil by letting the water run out the drain holes until the water runs out clear.

Citrus are self pruning so you don't need to remove the flowers. The symptoms may be caused by mesophyll collapse. I've inclued a link to its description. Scroll down a little over half way to get to it.
http://aggie-horticulture.tamu.edu/citrus/l2315.htm

bettydee - Thanks for your prompt response. You are right, there is a bit of curling in the leaves because we had some construction last summer and the poor plant was moved around a bit and it had some problems this summer, but I don't see anything now. I do look carefully but I will look again.

It was not in good condition at the end of last winter. It usually suffers a bit indoors, and yes, I did some significant top pruning as well at the same time as I root-pruned. I have to keep it in a container so I do both regularly. I have stones in the bottom for drainage and I water once a week, a bit from the top to moisten the fertilizer, and from the bottom so the roots will grow down . When I repotted it I followed the directions for citrus soil. I forgot about the pH meter. We have one somewhere. I'll find it ASAP. Two years ago it looked like the attached photo. It does sound like Mesophyll Collapse. I wish they had a photo with the description. I found photos on other plants, but not on lemons. Thanks for the many suggestions. I'll recheck everything.