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Lemon trees are often kept in tubs and Mediterranean gardens because of their appearance and the fruit they produce. In addition to various pests, there are 10 common lemon tree diseases that you should definitely know.

Notice: We have shown some diseases as examples with pictures of other plants so that the diseases are recognizable.

yellowing disease

Yellowing is one of the most common lemon tree diseases. With these, the leaves begin to turn yellow and curl up, dry up or fall off the tree. However, it is difficult to determine the actual cause, as there are numerous triggers for it:

  • waterlogging
  • persistent drought
  • high pH of the substrate
  • too dark location
  • too cool location
  • nutrient deficiency

That means you need to double check what might be wrong with the plant or what is causing the problem. Typical for Central Europe, for example, are heavily calcareous soils or hard water, which has a negative effect on the pH value of the substrate. The trees are sensitive to lime and prefer an acidic substrate. Nutrient deficiencies are usually related to an iron deficiency. A magnesium deficiency is also often the reason for chlorosis on the lemon tree. Once you figure out what's causing it, you need to adjust the appropriate conditions. Rarely, removing the yellowed leaves is recommended when they have already dried up.

Notice: In older specimens, the tree may turn yellow and shed some leaves before new ones are formed. The trees remove the chlorophyll from the respective leaves.

sunburn

Yes, even a lemon tree can get too much sun. The reason for this is not a location that is too sunny, but a plant that is not adapted to the Central European climate. If the specimen is transported outside of winter quarters without hardening, it will have a hard time withstanding the warm temperatures. The roots in particular suffer and cannot transfer the required moisture to the leaves. This can be recognized by the following symptoms:

  • bright spots are formed
  • irregular shape
  • scarred brown
  • stains yellow
  • dry out
  • take on a light brown hue

Depending on the intensity, the course of the disease can be quite rapid. Fortunately, sunburn does not directly affect the tree. You can simply remove and discard the infested foliage if the case is severe. Otherwise just leave the leaves on the tree as the green parts are still useful for photosynthesis. Next year, be sure to get the tree used to full sun in the spring.

Notice: If only the edges of the leaves are brown, the trees are over-fertilized. While this rarely happens as lemon trees are very hungry, you should reduce nutrient additions.

root rot

One of the most dangerous diseases that can affect a lemon tree is root rot. This is triggered by waterlogging, because lemon trees should never be watered excessively or planted in compacted soil. You can recognize root rot by a sudden loss of flowers and fruit. The lemon tree is also visibly weakening. If you suspect waterlogging, check the substrate in the bucket. If this is very wet, you must assume the disease and repot the plant immediately:

  • Carefully remove the lemon trees from the tub
  • Remove roots completely from substrate
  • check roots
  • remove dark, thin roots
  • also remove dead, rotten or dried out ones

If the root rot is well advanced, you will either need to cut away a large part of the root ball or discard the entire plant. You should never put them in the compost afterwards, as root rot is often accompanied by fungal infestation. Household waste is used instead of compost. After freeing the plant from the wet soil, you need to repot it. The substrate should be as follows:

  • high-quality garden soil
  • airy
  • create drainage
  • Drainage material: gravel, potsherds, screed sand
  • enriched with mature compost

If you use screed sand as a drainage material, this is simply mixed directly into the soil. Place gravel and shards of pottery at the bottom of the pot, which should also have drainage holes. After that, you should only water as needed. This means that when the top layer of substrate has dried, water them.

sooty mold

Sooty dew on a rose petal

The disease is caused by lemon tree pests. In this case, it is scale and aphids that can make life very difficult for citrus limon. Sooty mold is visible on the plant as black leaf spots that are irregularly colored. In many cases honeydew can be seen because the lice produce which in turn can attract ants. This is a little less common with a lemon tree, since in Germany they are usually kept in tubs. Remove the affected leaves and pests to eliminate the disease.

mildew

Powdery mildew on maple leaf. Source: Jerzy Opioła, Powdery Mildew Acer DK43 (1), crop from Plantopedia, CC BY-SA 4.0

Powdery mildew is one of the diseases that can affect even healthy plants. Various powdery mildew fungi spread on the trees when they are too close together and there is high humidity. The trees must also be able to breathe. Fortunately, you can remove the white to gray coating on the top or bottom of the leaf with classic home remedies. If the infestation is severe, you should remove the leaves and create a good environment in which the lemons will thrive.

Fusarium

One of the serious diseases that can affect your lemon tree is Fusarium wilt. The fungal disease occurs particularly frequently in specimens that are mainly kept in the greenhouse. The fungi can multiply much more easily due to this attitude. In most cases, they are introduced through the selected substrate if this has not been sterilized before use. The symptoms are:

Fusarium wilt on a field bean, Source: Jerzy Opioła, Fusarium sp (4), Edited by Plantopedia, CC BY-SA 4.0
  • Foliage brightens
  • falls off
  • Affected shoots die off
  • branches discolour

If the infestation is not treated, the trees can die. If they don't die, growth will be severely restricted. As soon as you notice the symptoms, you must completely remove the affected parts of the plant. Also repot your plant so that it receives fresh substrate. Sterilize this and the citrus limon will be much better off.

scab

Depending on the intensity, scab can pose a problem for the lemon tree. Especially in the humid regions of Central Europe, the disease caused by Elsinoe fawcettii fungi is not uncommon and noticeable on the leaves and fruits. Persistent moisture causes the fungi to get into individual shoots, and from there they get into the foliage and lemons. An infection can be recognized by the following damage pattern:

apple scab
  • Pustules appear on the top and bottom of the leaves
  • Pustules appear on the skin of the fruit
  • Red color
  • leaves cripple
  • Fruit mostly inedible

Remove all infected plant parts immediately and do not dispose of them in the compost. It is important to prevent the scab so that it does not strike again in the next season. To do this, collect the autumn leaves, because the fungi overwinter on them and infect the lemon tree again the following year.

lack of light

Diseases on the lemon tree can be caused by a lack of light. Being a Mediterranean plant, it needs plenty of sun and constant warmth to thrive. In most cases, a lack of light can be seen in the spring. The new sprouting ensures horny shoots that are significantly thinner and mostly bare. They rarely have single pairs of leaves. Remove the horny shoots and provide the plant with enough light. The shoots negatively affect the lemon trees, making them more susceptible to other diseases.

lack of water

The lack of moisture is also one of the typical diseases of lemon trees. A lack of water is particularly common because the plants are kept in tubs outside of their original distribution area and can therefore only create a limited supply of water without waterlogging occurring. A lack of water is noticeable by the following symptoms:

  • Tree looks weak
  • Leaves curl up
  • whole tree affected
  • location dry

If you don't start watering enough, the lemon tree will dry up in the near future. This condition occurs particularly frequently during the vegetation period, since the citrus plants put a lot of energy into budding and flowering during this time. To bring the tree back into shape, you need to give the root ball a bath:

  • Prepare bucket
  • slightly larger than root ball
  • fill with lime-free water
  • Get the plant out of the bucket
  • put in the water bath

Soak the root ball well with water until no more air bubbles can be seen. Then you can pot it again. It doesn't hurt if you check the drainage. Then you should always make sure to water when the plant needs it.

Notice: If you find curled leaves on just one branch or shoot, it usually needs to be removed. The shoot is damaged and negatively affects the vitality of the rest of the plant.

Winter leaf fall

Source: FASTILY, Lemon Tree 4 2022-11-21, Edited by Plantopedia, CC BY-SA 4.0

If the leaves fall in the selected winter quarters during the cold season, the reason is overcooled roots. Here's the problem. Even with lemon trees that are in the perfect winter quarters, the root ball can freeze. As soon as you notice the following symptoms on your lemon tree in winter, it can be assumed:

  • Leaves brighten
  • curl up
  • fall off

Rarely, the plant can appear weaker, which is typical for such diseases. In order to additionally protect the root tissue from cold damage, it is advisable to use a heating mat that is placed under the pot. In addition, the plant should be placed a little darker so that it does not sprout too early, which would cost it a lot of strength.

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Garden plants