arnagas
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Joined: Tue Dec 13, 2016 8:26 am

What is this on my lime tree?

Hi
It seems to be killing the tree. Some leaves look like they have been partially eaten but I do not see any insects, caterpillars, or ants on the tree or leaves themselves
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SQWIB
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Joined: Tue Feb 16, 2016 9:21 am
Location: Zone 7A - Philadelphia, PA

Lichen?

arnagas
Newly Registered
Posts: 6
Joined: Tue Dec 13, 2016 8:26 am

Hmm yes after searching it does look like that. I also read that it does not kill the tree.
Somehow though my tree is dying. It is drying up and the leaves look eaten (see attached) Any thoughts on what it could be?

Location is Florida
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imafan26
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Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

It is indeed lichen. It is usually from wet conditions. Citrus trees are tropical trees that like heat and lots of sun but while they do need water, they require excellent drainage. There is a lot of lichen on the tree so it is in very wet conditions, probably wetter than the tree prefers. If the ground floods at any time, you can get root issues. There are several diseases and pests that can make your tree look like this.

1. Water issues - causes root damage. If the root to canopy ratio is not maintained you will see more twig
die back. This can be caused by over watering killing roots or from under watering causing leaves to yellow curl and drop. Citrus are not tolerant of salt or poor drainage. Citrus like a good soak and to be almost dry before the next watering. Leaves will curl, yellow, and drop if they don't get enough water.

2. Pest pressure: Pests like citrus aphids, scale, Asian psillids, white flies, thrips, mites not only feed on trees but can bring viruses and diseases which eventually will cause the decline of the tree.

3. Soil/fertilizer Citrus trees are heavy feeders. A mature tree should be fed regularly. I feed mine whenever the new leaves come out and again after fruiting. Some of my citrus get fed multiple times of the year because they produce continuously. Persian limes only produce one crop a year for me so it only gets fed when the new leaves appear and after the harvest in September. I have potted citrus so I feed them Vigoro citrus food 6-4-6. The amount is dependent on the diameter of the trunk and how often the tree fruits.

4. Pruning. Citrus trees do have some die back and dead branches should be pruned off. It is better to prune citrus trees a little after the flush to open up the canopy, and control the direction of growth. Trees should not be heavily pruned. Pruning more than 30% of a fruit tree usually results in no fruit for 2-3 years until the canopy grows back.

5. Control pests: Citrus aphids, mites and thrips will attack the new leaves and flowers. Whiteflies, Asian psillids, scale are opportunists and will attack plants that are weakest first. Citrus Tristiza virus, if pretty much rampant in Hawaii. We can only graft onto resistant rootstock which slows but does not stop the disease. The trees usually succumb in 25 years. Some trees are more resistant and can live 50 years.
Florida has Huanglongbing = citrus greening disease. It is a virus transmitted by the Asian psillid and is always fatal.

Your tree does not look that old but it is in poor condition. Something is chewing on the leaves and the leaves are yellow. Prune back the dead wood on the tree. Make sure your pruners are clean and sharp.
Control the pests on the tree. Look under the leaves and on the stems for aphids, scale, whiteflies. Snails, slugs, and beetles will show up after dusk. Once you identify the pests, treat them appropriately. For most sucking pests, I just blast them off with water. You have to do it daily. If you haven't done it yet. Feed the tree. Check the soil and fix any drainage issues. For now hand water the tree. Use a probe to check soil moisture to determine how often you need to water the tree. The lichen does not harm the tree, but it is a sign that the branches are seeing a lot of moisture. If your soil has phythophtora, you will not be able to save the tree. You can replant the tree in good soil or just keep the tree in a pot. Citrus trees do well in pots of appropriate size. I have 14 or so citrus trees. A couple have escaped and I will have to kill them. The only way I can keep that many trees is to keep them in pots to control their size. My oldest tree is a kaffir lime and it is about 28 years old. It looks a lot like your tree, but mine is near the end of its life.

P.S. I plant most of my citrus trees in pots ranging from 2 gallons to 20 inch pots (mature trees). I plant in pure black cinder and the pots are watered daily and fed a combination of osmocote every 6 months and vigoro citrus food 6-4-6. My trees range in age from 3-28 years old. Many of my trees are grown from cuttings or are grafted. Meyer lemons, calamondin, and grapefruit are resistant to tristiza so they can be grown from cuttings. Others need to be grafted or they will only live a few years. You can use potting soil in the pots, but I don't like to repot, that is why I am using cinder. It makes it very hard to move the pots and they have to be tipped regularly or they escape.

https://edis.ifas.ufl.edu/hs141



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