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Hello Everyone, I am a first time poster and an armature condo gardener. I am in a US zone 5 or Canadian zone 6 and my plant is always indoors. I was given a small Meyer Lemon tree as a gift from Home Depot about 2 years ago. When I received it there were about 7 small green lemons already growing. It was in a very tiny 5 inch square pot that I re-potted into a 24 inch pot. After about several weeks the leaves started to develop lighter green spots like the picture below.



At first I thought I was under watering it and the leaves continued to fall off for another 2 months. Then I tried the opposite of under watering it. I tried adding fertilizer for citrus plants and still no effect. Eventually almost all the leaves fell off along with 6 of the 7 lemons. The last thing I tried was to spray it for spider mites as this seemed a possibility from what a read online. Eventually the one lemon ripened and three prances still had more than three leaves on it. I was about to write the tree off as good for dead as it looked pretty bad, but I thought I would give it a couple more months. about a 4 months ago I had a huge growth spurt and leaves returned to branches that we bare and I even got about 20 blooming flours which about half look to start developing small little lemons. The problem is that now the light green spots are back! if I cant solve this problem then I expect the tree will really die this time. Anything that you guys can help me with would be great!

The only other conditions that have changed that relate to this is that the problem seems to occur now at fall time. But as I understand a meyer lemon tree should not lose its leaves. Also it is an indoor plat, at this same time the heating comes on which might be a factor, but I don't think it is. Also as it is right beside a window is it possible that a draft would affect the plant this way? The current leaves in the picture are about 1 meter from the window so I don't see how that could cause any harm.

Get a magnifying glass or loupe 30x is a good one but 10x should still work. Look under the leaf and see if you see anything on it. Thrips, whiteflies, aphids, could all cause light areas on the leaf like the one you are showing. So could over watering.

If the lemon has bright light it can stay indoors. Please update your profile with your zone and location. It helps us when you ask questions in a post and you won't have to keep telling us all the time. If you live in a frost free zone, the tree will be happier outside.

It is hard to water a pot indoors because it dries out slower. A five inch pot to a 24 inch pot is a big jump for a plant. If the pot is too big it will take longer to dry and citrus likes deep watering but well drained soil. I would have gone to maybe a 1 or 3 gallon pot at the biggest from a 5 inch pot. Citrus like well drained acidic soil with a pH of around 6-6.5.

Citrus trees do have growth spurts, that is normal and they usually do not drop all their leaves.

I would check the roots and see if they are healthy and not black or soft. If they are either, you have no choice but to try to repot in a smaller pot. Cut off the dead roots with a clean pruner. Depending on the size of the root mass, I would just get a pot that has maybe 2-3 inches larger in diameter than the root mass. Personally, I don't like to repot citrus trees often so I do something that most people will not do. I plant all of my citrus trees in cinder. Air space and drainage is the most important thing for keeping citrus happy in a pot for a long time. Cinder allows for good drainage so don't mess it up with a saucer. No saucer under the pot. If you have to use the saucer, turn it upside down and use it as a pedestal. Cinder has no fertilizer. I use citrus food, Vigoro, I get it from Home depot, but any citrus food will do. Read the label, most times the fertilizer application depends on the diameter of the trunk. For a 1 gallon pot, 1 tablespoon in the spring with the first leaf flush and another feeding at fruti set at the end of summer is enough. If you want you can supplement with miracle grow for acid loving plants 1/4 strength once a week. (Weakly, weekly feedings). You don't have to use cinder, but it needs to be an acidic well drained mix. You can add some organic like peat moss or coir to a cactus mix to hold water longer. Cactus mixes tend to be alkaline so add a little bit of sulfur or use miracle grow for acid loving plants. I contains sulfur so it is an acidifying fertilizer. Black cinder is neutral. So is blue rock, but blue rock is much heavier and has fewer air spaces. If you want to make your own mix:
1 part peat moss or coir
1.5 parts number 3 or 4 perlite (large perlite, not the fine number 1 or 2.)
How often to water depends on how fast it dries out. If you can't tell and it can be hard to tell with cinder, get a moisture meter. Overwatering houseplants is the number one problem with most houseplants, second is not providing the right kind of light. Getting a combo meter can really help with those issues.

https://www.amazon.com/Moisture-Meter-Li ... B007FMVOVK

I call it the plant happiness meter. Mine is more for fun and it is not the same model as this one. This is just one that I found on the search. I think it just has a guage. Mine makes a sound; the faster the sound the happier and wetter it is. When the plant is dry the meter sounds off very slowly. The light sensor, I use to determine if my orchids are getting the right light. It is more of an empirical way to judge light. The other way is to look at the leaf texture (soft and dark green is too little light, Yellow or red and thick leaves means they are getting more light than they need, medium green, firm leaves= just right). You can use the light meter on a camera too. 10,000 lumens is full sun, 8,000 lumens is about 35% shade, 5,000 lumens is about 50% shade, 3000 lumens is 70% deep shade. Moonlight can be as low as 0.25 lumen. A lumen is the amount of light that reaches an object or foot candles per square foot. The light source is usually measured in foot candles of output.

I'm with imagine on this one KingMinster,
I suspect red spider damage. Their not really spiders but are very tiny mites. You need a lens to see them.
If you see it is these tiny mites then phytosylis will do the job of controlling them. These are extremely small critters that munch red spider with great relish.
They come mixed in bran usually and you just scatter this over the leaves of your plant. many thousands in just a small pot.

Very useful for cucumbers and toms too as no spraying needed.

Sorry ....incorrect spelling....should read phytoseiulus

I don't know about a Canadian source, but I came across one out of Arizona that offers several different species including the one JONA recommended. JONA, what are your thoughts on these others? Do you have experience with them as well?

https://www.arbico-organics.com/category/mite-control

Mite Predator, Amblyseius andersoni
Excellent choice for pre-emergent control of mite infestations!

Mite Predator, Amblyseius swirskii
Excellent beneficial mite for warmer growing conditions!

Spidermite Destroyer, Feltiella acarisuga
Use these predators for control of widespread spider mite infestations.

Mite Predator, Galendromus occidentalis
This is an excellent mite predator for use in hot and dry cropping environments–particularly effective against spider mites on orchard crops.

Mite Predator, Mesoseiulus longipes
This mite predator is an excellent control for spider mites in hot greenhouses with low humidity.

Mite Predator, Neoseiulus (= Amblyseius) californicus
This mite predator survives low spider mite densities by feeding on pollen and other small arthropods. Survives a wide range of temperatures and can tolerate lower humidity (40%RH).

Mite Predator, Neoseiulus (= Amblyseius) fallacis
A general predator for many different mite pests. Survives well when pest densities are low.

Mite Predator, Phytoseiulus persimilis
A great mite predator for spider mites in humid greenhouses and for dense field crops.

Spidermite Destroyer, Stethorus punctillum
Both the adult and larval stage of this predator consume hundreds of spider mites on cucumber and pepper plants. Compatible with predatory mites.

Wow thanks for all the responses. So I took a look under the leaves with a 10x loupe. I did not find anything crawling around, but I did notice that under most light spots there seems to be a brownish growth/stain that I could not get off. I tried to snap a pic I hope it helps. Also I tried the "paper" test where you place white paper under the leaves and gently shack it to see if anything falls on the paper, but that also resulted in nothing.



I also thought I should snap a picture of the actual plant in its pot. Let me know if you think the pot is too large. Also I have been too scared to prune it as it has so few leaves.



I may have just over watered it recently, after the spots started as I got scared. But I just ordered that moister tester to see if that is the case.

Let me know if these new pics lead to any other additional information.

We've used both a
Amblyseius and Phytoseiulus , with great success. Haven't used the others I'm afraid. We use them both under glass but outdoors we find that Phyto... seems the better.
Guess it depends on price and numbers required.
Remember folks though....you have to have the mite present there in the first place. Commercial growers actually introduce the pest into the crop first...then the predator so that a balance is set up where control is just right for good cropping.

KingMinster....the red spider mites are extremely small and would not fall off in a paper test. However I must say that that last photo you put on does not look like serious mite damage. Also mites do in severe attacks produce a webbing rather like a true spider web under the leaf. No sign of that of your plant though.
All I can suggest, if no further suggestions come forward, is that you keep a close eye on the lesions and see if they get any larger.

Citrus don't like to be pruned much. That is why I only lightly prune mine every year to keep it in shape.
I see some brown patches where the light areas are. It could be necrotic areas or areas of feeding damage. Can't really tell. I have no idea what the white spots are.

The pot size actually looks o.k., but you have to choose a pot based on the size of the root ball and not on the size of the top.

JONA with the phytoseiulus I see I can buy like 1,000 of them online, but is it ok to release them in my Condo? Not even going to get into how I will explain this to my girlfriend. Also it says that I should have 60% humidity. I know that during this time of year with the heat on my condo only averages around 30% humidity. I have also been thinking this may be a cause of my problem so I am looking into getting a humidifier. Not just for the plat but for me too!

You won't even see them KingMinster so don't worry about telling your girlfriend!
These tiny predators will only survive as long as there are mites for them to eat. Once the pest has gone..the Phyto will disappear.

Yes spider mites hate humidity; dry conditions are very conducive to them. The humidifier should be beneficial for both you and your tree. You can also help your tree by misting the leaves daily or at least several times a week. I have found that most of my house plants thrive with a misting regimen.

Thanks a lot guys. One last thing for now. Should I go try the humidifier first then try the phytoseiulus, or should I just do both at the same time?

I'd take the plant outside and hose down the undersides of the leaves well with water and dip the top in a bucket of horticultural oil and water for a couple of minutes. It is the best way to ensure good coverage. Most of the time nature takes care of the mite and thrip problem for me with a good rain. Oil will smother mites and thrips.