Presumably all three are near each other and suffering equally? Leaves yellowing and dropping can happen for all sorts of reasons - pests (mites); under- and over-watering; under- and over-fertilising.

If mites are the problem, they're incredibly tiny and very hard to see. They would resemble tiny specks usually on the underneath side of the leaf. A spray with something like white oil will clear them.

How often have you fertilised the trees? And have you kept the fertiliser away from the trunks?

How often have you watered them? And is their soil well drained? Citrus like a drink, particularly in summer, but they hate soggy ground.

all three are very near each other -- they're planted in a triangle, each about 1m away from the others. they all have yellow leaves, but the lemonade is the worst effected (whole branches are leafless), followed by the lime, with the blood orange having only a few effected leaves.
the spot where they're planted is in full sun, and used to have a lemon tree on it. i reluctantly killed off the lemon tree because half its trunk had split off, and what was left was full of borers. preparing the site thus involved digging out the lemon's roots, which left a hole a bit more than 1m deep and about 2m wide. i filled this hole with a mix of one third cheap potting mix, one third dynamic lifter potting mix (not straight dynamic lifter!), and one third garden dirt (my soil's not great, but it inevitably has a bit off goose-poo in it, as my pet goose likes to "help" me garden). then i planted the trees, and they're raised up a bit above ground level. they're mulched with bedding straw, and the lawn is kept well back from the trees (lawn right up to the trunk was probably part of the old lemon's problem), as is the goose.
in the centre of the triangle, i planted some oregano. when the oregano starts looking a bit wilty, i water the trees -- usually with a sprinkler for about 45 minutes to an hour at dusk; that probably happens about twice a week when it's hot. a few weeks ago (about 5 months after they'd been planted), i gave them some slow-release citrus food... i only gave them the recommended amount, and i don't think i got it too close to the trunk, but i could be wrong.
i don't think it's mites... i have mites elsewhere in the garden (on some native violets under a peppercorn tree -- i also have rust on a few trees, including a new dwarf almond... my garden's a disaster!), and they make things go a different kind of yellow, if that makes sense? this is a really bright yellow, and the veins stay green until right before the leaf drops off.
i'm pretty sure it's something i'm doing wrong, but i don't know what!
the fact that they've all started new leaves in the last week gives me hope, but the balding branches are upsetting.

This is something I copied and saved from the citrus forum, some time ago. I hope it helps. Obviously the conclusion was for that case in particular, but the info in the body is fairly generic.

Totally yellow leaves with no variation in the color, or yellow-orange veins with some green out on the sides, could be severe nitrogen deficiency, which may be due to an actual lack of nitrogen, OR could be due to injury to the roots (digging, weevil grubs) flooding, or damage to the base of the trunk (weed-eater), etc.
Less severe N deficiency will tend to show up more on the older leaves, while the newest leaves will have some green.
Yellow new leaves, with no pattern at all (just like N, but on the new leaves as opposed to the old), could be sulfur deficiency. Most Florida soils are sulfur deficient, and some blended fertilizers don't supply it.
If newest leaves have green veins on an otherwise yellow leaf (no border area around the vein; just the line-like vein itself), that would be iron deficiency, caused by a lack of iron OR a soil with too-high pH, OR again, severe damage to the roots or lower trunk.
If the newest leaves have green veins WITH green border areas to the sides of the veins, on an otherwise yellow leaf, and the leaves are normal size, it would be manganese deficiency.
If it looks just like manganese deficiency (green veins, green borders, newest leaves) but the leaves are dwarfed substantially, that would be zinc deficiency.
If on the older leaves only, you see a leaf on which the lower center portion is green and the tips and sides are yellow, with the green area looking rather like an inverted "V" or like a christmas tree, that's magnesium deficiency.
Iron, manganese, magnesium, and zinc deficiencies are often due to high soil pH, rather than an actual shortage of the element in the soil.
If your house is concrete, is there a chance the citrus trees are planted over buried concrete waste? If so, that would bring up the pH to 8.0 or even higher, and you may be seeing a mixture of all of those deficiencies.
I would not recommend a heavy application of N at this time of year, since it will inhibit the trees' becoming cold-hardy. It would be ok to apply any of the other elements, though. Then in mid-February, start your nitrogen fertilization.

Seems to me your soil pH is out. Perhaps the goose poo is alkaline?

now i'm really confused!
i went and had a closer look at the yellow leaves, and they're all different!
some are green with yellow veins, some are yellow with green veins, some are green with yellow mottling, some are more yellow at the tip, and some are more yellow at the base.... the only constant seems to be that they eventually go entirely yellow and drop off, and it's all adult leaves -- the new baby leaves seem to be fine.

should i be getting a soil pH testing kit, then?

sorry to be such a nuisance... it's just that all my fruit trees keep dying, and i don't know what i'm doing wrong. all the other plants seem fine, but the fruit trees turn up their toes and die. it's quite upsetting.

catslave

I agree with pepino about the pH. If your soil is similar to my mums in WA, then the soil tends towards alkaline...Mum worked in a nursery and she lamented people watching Burke's Backyard and giving their citrus dynamic lifter, which increased the alkalinity of the soil. She also said that growing a lemon tree near the chook pen was a no no too. That is only ok if you have clay soil

i'm in adelaide, so i think i do have clay soil. if i dig down about 15-30cm, the dirt's kind of orange-ish and sticky, which is clay, isn't it?

It sounds like clay, which isn't all that conducive to good drainage, and the mix into which you planted the trees also sounds like it was a bit lacking in nutrition. BTW, how did you kill off the old lemon?

Has the watering pattern been dictated by the condition of the oregano? For what it's worth, oregano's one of those herbs that thrives in tough conditions. Mine gets next to no special attention, even through summer, and it thrives. I'd forget the oregano as an indicator and plan the watering around the trees' needs. As I said, citrus likes water, patricularly in summer, but not soggy ground. Does the water drain away?

Young citrus also like regular feeding. Mine are now three years old and, from their early days, I've fed them about once every six weeks with a lesser dose than is recommended for the traditional two or three times a year feeds.

Anyway, try a process of elimination. As pepino and mercury suggested, test the soil's pH. If the pH is crook, it doesn't matter how much goodness is in the soil, the trees can't access it, and excess acidity or alkalinity will lock up different nutrients respectively. Citrus like a pH of between 6 and 7. If the pH is crook, adjust it. Once it's in the right territory, watch the trees to see what happens. They could be all right again. If the problems persist, and if you've already eliminated wet feet as a problem, you can be pretty sure you've got soil deficiency problems.

And don't worry about the trees dying just yet! :) The diagnosis will take a little while to surface, but the trees will cope till then.

i killed off the old lemon by chopping it down and digging out the roots! so i don't think i've poisoned the new trees.

just tested the soil pH, and it's neutral, so it's probably not that, either?

i have, though, been letting the oregano's condition determine watering... when the oregano gets really wilty, i water the citrus.
so i'm probably under-watering?

i'm sure the citrus can be saved, it's mostly my track-record that makes me afraid for the poor things. :-p
i've already done in a pear-tree (i think it had crickets nesting under it?)... i have a mandarin tree that seems quite healthy, except for the fact that it's the same height now, 3 years later, as it was when i planted it (2 foot)... there's the rust on the almond (which i can't spray because of the goose)... and then there's the persimmon, which is on death's door, and i'm starting to suspect that i'm desiccating that, as well....
i don't know that i can be trusted with trees.

Okay, if the pH is neutral, it's probably a nutrient deficiency. Although has it been determined whether the soil drains well? With clay 15cm beneath the surface, water could be being trapped, and citrus hate standing in water. If the soil is draining well, you could reasonably expect to give citrus a good, deep drink once (or even twice) a week in the heat of summer, scaling back to every two or three weeks in cooler weather subject to decent rainfall. Water, particularly, around the drip line - beneath the outer-most margins of the branches. That's where the growing roots are. Don't let water gather around the trunk for too long.

Citrus like consistency in both watering and feeding. If I read your post right, they've only had one feed in five months? That's not enough, particularly for young citrus, and it could be the cause of the deficiency. I'm of the feed-them-a bit-less-more-often school rather than the big-feed-twice-a-year school. Try giving them a couple of good handfuls each of citrus food about once a month. Spread it out well around the drip line, where the growing roots are, away from the trunk.

And keep the mulch well away from the trunk as well or you'll have a rot problem.

Pepino's very good info from the citrus forum covers most of the possible deficiencies. The starting soil was low in nutrients, so regular feeding should address the problem to some extent. You should see an improvement. It might not be the complete answer, but only time will tell. If, after a couple of months, there are still signs of deficiencies, you can target some of the specific nutrients and add them.

Citrus are pretty simple beasts: give 'em plenty of food, water and sun and they're laughing!

Forgot to add that it's wise to water immediately before and after you add the citrus food.

Hi catslave,
I'm no expert on citrus, but I am wondering if this could be corrected with a dose of trace elements. You can buy these readily at any garden supplier, nursery etc.
Cheers,
Dee.

The order of severity you mentioned seems typical of each of the varieties with the Lemonade being most sensitive (in my experience).

I give mine a citrus feed called Thrive. Not sure of its composition off the top of my head. I give them approximately a large tablespoon of it at the change of each season. As Finbar says less more often is probably better but I forget and tend to feed them in the first month of each new season. I fed mine the night before last being the official change of season for the rest of the world. I don't feed mine when the next day is going to be hot either.

I have in the past fed with Epsom Salts and Lectric Soda. Not sure what each one is good for but they all look healthy at the moment. I do prefer the Thrive as it is balanced and slow release.

If you do opt to go for Epsom Salts or Lectric Soda, use it carefully to start with. I only fed mine small amounts once. Unless you do a full soil analysis you don't know what is in it and you may be adding to the problem.

Above all I prefer good mulch around the plants. It encourages worms, which in turn work the soil and even my clay ground has improved because of them. Just don't put too close to the trunk.

I have just found a link I saved some time ago with sick citrus symptoms and pics of what they look like.

Here is a link that might be useful: A Guide to Citrus Nutritional Deficiency and Toxicity Identification1

Some of my lemons have little pointy bumps on them, and the fruit has a small patch of brown on the inner side of the pith, extending into the outer margin of the fruit. Is something stinging my lemons?

Are the small pointy bumps at the end Finbar? LOL.

If they are elsewhere, I have seen this and not sure what it is or what causes it but doesn't seem to adversely affect the fruit. I have seen some severe deforming in lemons, which takes on the shape of a Buddha's Hand citrus - nearly all rind.

I've never seen the other problem you have. It may be something that occurs in warmer areas.

Hello

I'm having a similar problem with my 2 year old potted meyer lemon. Some leaves are yellowing and dropping off, which I've heard can be from under or over watering. But I use a moisture meter to water, and measure at root level, so I don't know how that could be a problem.

It's potted in a 10 gallon pot with plenty of drainage holes and it gets around 6-8 hours of full sunlight. It just sprouted out at least 20 new leaves about two or three weeks ago, and those look a little wilted in comparison to the older leaves which look yellowed. How can half of the plant look overwatered and the other underwatered?

I'm just really worried I don't want to kill this tree, it was doing so well two weeks ago!

Hi Nicole
I'm not sure where you are located, but I'm guessing it was warmer 2 weeks ago and now that the weather has cooled your plant probably has too much moisture around the roots. You will find in large containers there will be a vast difference in moisture levels from the top to the bottom. See if you can test the moisture through the drainage holes. If you find it is moist, hold back on the watering and ensure you don't overwater through the winter months. Depending how much sun the plant will receive I think watering a plant in a pot that size is only required about once a week. You will need to monitor how quickly it dries. If it is in a saucer or water-well I'd take it out and then if you want to use it, only do so through Summer.

Good luck

I'm in Savannah, Georgia. Mine doesn't sit in a saucer or anything. I also tested the moisture from the bottom and it seems okay.

It's not dropping leaves anymore--perhaps it was just a little cold spurt that bothered it.

However, it does have 6 or 7 leaves that are yellowing from the tip. They have brown points and are curling up. It's only on older leaves, also. What could this be from?

Hi Nicole
Try the citrus forum. There will be much more knowledgeable people there that can help you.

Good luck

Here is a link that might be useful: Citrus forum