i can't tell what's causing it. the yellowing could be a deficiency. have you fertilized it recently?

what's the watering schedule?

Oh, I water it a couple times a month. A slow trickle for several hours at a time.

I bought some fertilizer but haven't used it yet, have been unsure what to do.

The brown spot with yellow around it may be alternaria. It can be controlled by a copper spray. If you have a good nursery near you, try taking a leaf in a plastic bag to have them verify it.

I agree with lgteacher. It looked fungal, and considering we have had an abnormally prolonged humid August and September, this could certainly be the culprit. Good eye, lgteacher. If you Google Alternaria in Citrus, you will see several images that look like what you're seeing on your leaves. I would make sure the tree is pruned to remove any crossing inside branches, to allow for better air flow through the tree, pick up any dropped leaves and debris from underneath the tree, and the spray with the appropriate anti-fungal spray. I believe this is treated with low-concentration copper sprays. But, good tree hygiene with opening up the canopy and raking up all the dead leaves and debris may end up eliminating the problem for you.

Patty S.

Is #3 isolating a tiny egg on a stalk? Or the fact that some of the leaf has been eaten. If not the tiny egg scenario, what do the eggs look like?

Yes, rhizo 1, that is a tiny egg on a stalk and a leaf that has been eaten. I haven't seen an egg up close. I took that photo with a zoom lens and captured the egg in the photo by mistake.

Now, does anyone know of a good nursery in the western San Fernando Valley, CA?

Thanks everyone for your replies. I'm going to try and find a nursery to take the leaves to and go from there.

Those little eggs on a stalk--Are they tiny and white on a white stalk?

They may be lacewing eggs and often I see those near places there are pests. The lacewing lays the eggs in places like that so the babies will be close to their "prey". The babies are very fierce and they eat all kinds of pests. The reason the eggs are up on stalks is so the first to hatch won't eat the rest of the eggs.

The larvae will attach all sorts of debris to their backs to camouflage themselves and will look like little bumps of lichen. Then, they trundle around looking to eat things, but they don't eat the leaves. I've had them fight with me when I've used a blade of grass to try and herd them toward an aphid. One of the was on the rim of a pot I had to move and I prodded it off the pot and onto a fig leaf, but it lost its footing and tumbled when it landed on the leaf, leaving a part of its camouflage stuck to the hairs on the fig leaf. It was stuck upside down with its little legs waving in the air, so I used the grass to turn it over. It then trundled away. I herded it back to it's debris that it had lost and when it came to the pile, it started picking the stuff up and putting it back onto its back. It was so cute to see. When it was satisfied it had put it all back on board, it walked off. The reason I used a blade of grass is they will give you quite a nip if you touch them. One of them bit me on the leg and it actually hurt. I smacked it thinking it was a spider, or mosquito biting me and too late saw it was a lacewing baby.

The picture of the egg is too small for me to tell if it is lacewing, but it looks like it.

Good luck with your lemon tree,

Vivian

Pam, try Sperling's Nursery.

Patty S.