It's obvious to me that the people who claim ants do not kill trees have absolutely no experience with fire ants or any knowledge of them....I've noticed they are all from more northern states than Florida. Yes, certain ants will kill trees. Fire ants kill trees and shrubs. They are a horrible scourage here and were imported from Brazil in the early 1900's into Pensacola via cargo ships. They are one of the most miserable creatures on earth, and a prime example of how careless importation of foreign species is so disruptive to another area. In Brazil there is a fly that keeps the fire ants in check there, and then other birds and animals that keep the flies in check, and so on. Here, our native species do not know what to do with them, and they have flourished and gotten out of control. This is all information given to me by our local extension office. They have become so bad since the last tropical storm on our property, (and other properties in our area that did not flood), that I can't garden or walk to my clotheslines without being bitten. The bites are horrible. They burn, sting, and itch all at the same time, and then the bite forms a nasty pustule. Imagine having 50 bites. Imagine a tree or shrub dealing with them. We are having our farmer's co-op come to treat our whole 10 acres. They are not just present at the mounds. They scout all over the place. Our property did not flood, unlike many unlucky people in my area, so the fire ants have migrated to properties that stayed dry. They literall float mounds of themselves on top of flooded areas. I saw it with my own eyes. They have killed 7 rose bushes on fortuniana root stock, 5 citrus trees, and several of my native holly trees so far since the storm. They eat the roots and they bore up into the trunks of the trees. Once established into and near the trees they are almost impossible to get rid of. I've tried everything, including drenches. I am going to have my husband pull them with the tractor and burn them. Since the roots are so damaged I could actually easily remove them with a shovel, but I won't go near them any more. In addition to all of this it appears that they have displaced many of our native ants, who do not bite, and whom are important to the balance of our ecology. They've even appeared to have eaten all our earthworms. I can't find any in my composted areas. So, unfortunately, we have to "nuke" our whole property and then try to introduce the beneficials back in. So yes, ants may have killed the original poster's tree.

Well, I would think that the ants are dying where they sit on the leaves, due to the residual malathion poison you're using. Then the dead ant bodies are just decaying. I never use an insecticide to treat for mites or aphids, especially something as nasty as malathion, as a hard spray with the hose gets rid of them for me. And, I make sure to keep the ants out of my citrus, as they will farm the aphids, making things much worse. I use boric acid ant traps as well as tanglefoot placed on a paper wrap around the trunk (never apply tanglefoot directly to the trunk, as it can heat up and damage the cambium layer), but my citrus are in the ground. I would think, though, that with a 30 gal. pot, you're probably fine using boric acid bait traps, which is again, avoids the use of chemical insecticides on a tree whose fruit you eat. Can't speak to white fly treatment, as I haven't dealt with that on my citrus or in my yard, fortunately. Patty S.

The ants themselves don't harm the tree, but they do "farm" aphids and scale, they collect the honeydew these insects produce. So often seeing ants is the first clue you may have aphid or scale or both. Ants do sometimes collect the nectar from the flowers, so if you have flowers but don't see any aphid or scale, they could just be after the flower nectar. Your leaves show some minor insect damage. First pic looks like you had some Citrus Leaf Miner damage a while ago, looks like old damage. They usually show up in fall and spring. Second pic looks like possible grasshopper or katydid damage. The ragged edges show that. Also looks like old damage, as the edges are healed up. Third pic looks like you may have some aphid damage there. They can often make new young leaves curl like that. The leaves also look to have a pretty bad nutrient deficiency, lack of nitrogen mostly. Might be time to feed your tree again with a good citrus food. Pyrethrins is a good low environment impact insecticide, but short term so you need to use it a few times over a few weeks to clean up an infestation. Make sure you do have an infestation of either scale or aphid currently before you spray again. Works well on sucking insects like aphid or scale, works better mixed with Neem oil, as long as your air temps are below 85*F. But Pyrethrins doesn't do much for Citrus leaf miner or chewing insects like grasshoppers. Spinosad works best for them, but it looks like your CLM is gone for now. You will want to spray that again in the fall when you get a new flush of leaves. CLM love the new leaves best, so if you spray the Spinosad on the new growth in spring and fall you should be fine there. On a larger tree like that, it's mostly just an annoyance, but it can stunt young new trees. Overall though your tree looks pretty good. Outdoor trees often will have a percentage of damage from insects and unless it's all over the tree, most mature trees can tolerate a percent of insect damage without any problems. But do look more carefully under the leaves and along the young twigs, as the ants can be a sign you might have scale or aphid somewhere on the tree. This link may help.Citrus Invertebrate Damage to Leaves

I'm a little late to the discussion, but I'll give my experiences in the world of growing potted citrus in case it helps. I live in South Central Pennsylvania where our zone was changed from 6a or b to 7a in the last year or so. I currently am growing meyer lemon, something that was labeled as "standard lime", and an arctic frost satsuma mandarin. I potted them all in unglazed clay pots because they dry out fairly well with less chance of root rot occurring as long as the soil drains well. The lime was the only plant that didn't give me any problems once I started watering it regularly. The 3 foot meyer lemon was my favorite and I decided to get a nicely decorated pot just for that one. The pot is maybe about 18" compared to the 12" and 14" the other two were placed in. The walls of the pot were much thicker than the other two as well. The soil itself was organic soil that comes pre mixed with compost and worm castings. I just added sand and micronized azomite to keep the soil well drained and enriched with trace elements. The lemon grew a few limbs and leaves last summer. It also flowered and grew lemons. My intention was to remove the lemons to allow for more leaf growth, but couldn't bring myself to do it! The problem was that the soil never dried out. I believe the thickness of the pot was the cause of that. Most of the leaves dropped off over the winter despite it being kept under a 600w high pressure sodium grow light and being watered the same amount as the other two plants. I just repotted the plant about a week ago and it started growing new leaves almost immediately. The new pot is 12" with the soil being recycled from the 18" pot. The citrus have been outside almost a month now since we've been out of the 30s. I wanted them to get some of this rain we've been getting to flush the soil out and to rinse the neem oil off that I sprayed them with last fall to get pests off before I brought them in for the winter. The lemons never fell off so I knew the plant wasn't close to dying, but I did notice the roots hadn't grown all that much since I potted the plant last spring. I think it should do a lot better now that the soil can dry out a bit between watering. As for the arctic frost, the plant never did much of anything from the time I planted it until about two months ago. It neither grew nor lost any leaves. It just stayed the same and I knew that wasn't what it was supposed to do. I knew that could happen if the soil level was raised higher than it was at the time of purchase but didn't remember adding soil. I later remembered that I pushed excess soil around the edge of the pot as if to direct water toward the trunk during waterings. That excess soil eventually leveled out and left almost two extra inches of soil around the trunk of the plant which was maybe two feet tall. I removed all the excess soil until I ran into roots. The excess soil filled about a quarter of a plastic grocery bag. I removed a little excess from the meyer lemon at that time as well. Within a couple weeks, the arctic frost finally grew new leaves and eventually flowered for the first time. The fruit started to grow, but I did remove those because the plant is way too small with too few leaves to be growing fruit in my opinion. As for the lime, It did just fine from the time it was potted spring of last year. It started flowering last fall or winter and hasn't stopped since. The fruit would get to about pea size and drop off during the winter, but as the length of our days increased and especially since I put the plants outside, the fruit hasn't been dropping. To sum things up, plastic pots retain moisture too much in my opinion. Clay pots allow for breathing and make it harder to damage plants due to over watering. You will have to water the plants more often, but from what I've experienced thus far, that's how citrus like it-quick drying soil with frequent thorough waterings. Misting the leaves is also appreciated by the plants. Given the hotter temps in Florida, plastic pots may be acceptable while outside. Root rot may become an issue if the plants are taken inside at all however. Something else to keep in mind is mentioned in a youtube video by an experienced citrus grower. He compared the growth of his citrus to that of his neighbors citrus plants. The neighbors pruned the plants heavily in a way that exposed the bark of the tree to a lot of sunlight. The trees never recovered from the pruning. He rarely pruned his trees and if he did, he did it in a way that allowed the branches to still be shaded by leaves. He stated that citrus, unlike apple trees, don't have to be pruned in order for more fruit to grow. Citrus will likely have more of a bushy growth while people prune them to look more like trees. Doing so with a potted plant will expose the trunk to sunlight, which they do don't want. It will also take needed shade away from the pot. The roots need to be kept cool like they would be if the plant were in the ground. Hot roots will result in poor growth as well. If the plant isn't wide enough to shade its pot from too much sunlight/heat, place other pots around it or something white/bright around it to reflect some of the light... I had to move due to not being able to find employment and my plants were stuffed in a closet at a relatives house for a few months with a florescent lamp. My gojis, navel oranges, jade plant, and original meyer lemon all died from lack of light and air circulation. Actually the navel oranges were placed in a very cold window sill with a thick curtain keeping any heat from getting to them and weren't watered for over a week... Of all the plants pictured, only the two bananas and the lime survived. The lime is front left with the vibrant green new growth. I'd only had it about 3 months at that time. The long branch was about two feet at that time. That very same lime plant is on the left in this photo after a much appreciated summer outside. This photo was taken almost a year after the previous photo. It really filled in! I guess it liked the bat guano ;) The plant in the middle is the arctic frost satsuma with a meyer lemon cutting rooting under the plastic jug. The plant on the right is the 3 foot meyer lemon plant. It didn't look too bad after the summer but the long winter started to take its toll... It flowered and started to grow lemons. Then flowered again. Then I decided to flush the pots. The lemon never dried out after that and I eventually ended up with this... It's now in a smaller, thinner pot that should dry out like I want it to. It's been cloudy/rainy the last few weeks, but I still found some growth on the meyer lemon. It was windy yesterday so the leaves are flipped over in some spots. The arctic frost is doing well with a few new leaves... And the lime is still doing well... I guess I've exceeded some kind of limit so I'll have to add the photo in another comment...