Yellow Spots on Lemon Leaves

Discussion in 'Citrus' started by englak, Aug 9, 2020.

  1. englak

    englak Active Member 10 Years

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    Hello,

    I have a young semi-dwarf improved Meyer lemon that is showing yellow spots on the tops of its leaves and brown blotches in corresponding locations on the backs of leaves. What is this, and how to I get rid of it?

    Your help is appreciated.
     

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  2. Sulev

    Sulev Active Member

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    Your container seems to be pretty minimalistic.
    I think, that your plant needs repotting to the larger container.
     
  3. Junglekeeper

    Junglekeeper Esteemed Contributor 10 Years

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    I've grown a number of Meyer lemon trees over the years that originated from the same grower and they all had this affliction to some degree. I am guessing it is some sort of bacterial or fungal infection. I ended up discarding the trees as a precaution against infection of my other citrus trees. Here is a similar complaint, with no resolution: What is ailing my Meyer lemon tree? The tree that I have now is similarly affected from the start but the problem exacerbated around the same time. Perhaps it's related to the environmental conditions at this time of year.
     
  4. Arlette

    Arlette Active Member

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    The cultivation of lemon in pots requires greater attention than that in the ground, the soil in the pot must have a neutral pH, must not allow water stagnation (well drained) and must be not very clayey. Obviously, as he rightly wrote Sulev, It must have dimensions appropriate to the size of the bread of earth. suitable for the size of the earthen bread. Generally it must be twice the circumference and height of the bread of earth that surrounds the roots of the plant.
    In pots, the substrate is subject to frequent washouts (rain, irrigation ... ...) so you will have to think about a suitable fertilization program from March to September to avoid loss of micro and macro elements (especially iron) and fertilization must be carried out periodically using a specific fertilizer for citrus fruits.
    It often happens that the leaves of citrus fruits turn yellow and the causes are many, the most frequent are:
    Incorrect irrigation: the lemon is affected by water stagnation, irrigation must be carefully dosed. A useful practice to understand if there is a need for water is to stick a finger in the ground for 2-3 cm if extracting it is dirty with damp soil you have to wait a little longer to give water, if instead it comes out clean it means that the substrate is also dry. below the surface and the plant should be irrigated.
    Furthermore, if the leaves of the potted lemon turn yellow, you are probably irrigating with water from the aqueduct which, in addition to being calcareous, is very chlorinated and therefore, before distributing it to the lemon tree, it is essential to leave it for twenty-four hours in containers open to allow the evaporation of chlorine and the deposit of limestone, discarding the one found on the bottom.
    The quantity and quality of the water must also be considered: in fact, each irrigation must be proportionate to the size of the pot (indicatively it goes from about 3-4 liters for pots with a diameter of 30-35 cm to reach 30-35 liters for pots of 60-70 cm)
    Poor drainage of the substrate: even if the irrigations are carried out correctly, water stagnation can occur due to a soil that is not perfectly drained. In fact, a layer of inert material (pumice, expanded clay, gravel,… ..) must be inserted at the bottom of the vase, proportional to the size of the vase.
    Lack of nutrients: If the leaf veins turn yellow and the vegetation is generally not very lush, it is likely that the tree does not have enough nitrogen. Nitrogen, among all the nutritional elements, is the most important as it influences all metabolic processes and promotes the growth of lemon plants. About 50% of nitrogen is stored in the leaves, while the remainder is divided between trunk, branches and roots. Therefore, the bright green coloring of the leaves is a great indicator of the availability status of the element.
    If the margin and the apex of the leaves are yellowed, but the internal portion and the ribs keep their green color, it is possible that the plant is suffering from a lack of magnesium.
    If the leaf turns yellow between the veins and growth is stunted, it is a clear symptom of a lack of zinc.
    If dark spots are seen on the lower plate of the leaves while the upper page is affected by evident yellowing between the ribs, the citrus fruit is suffering from a manganese deficiency.
    iron certainly plays a leading role. Its lack can be visibly detected by the yellowing of the leaves (ferric chlorosis), while an adequate presence of iron in the fertilizer for potted lemons produces an intense green color of the foliar apparatus, which denotes an excellent state of health and makes the lemon plant less susceptible to attack by fungal parasites.
    Phosphorus, which is stored in a high percentage in the roots, is mobilized towards the aerial part in spring and becomes indispensable during the reproductive phase of the lemon plant (spring summer).
    Potassium, on the other hand, plays an important role on the quality of the fruit, increasing its sugar content, firmness, aroma and taste. The contribution in summer is fundamental, also considering that potassium is more assimilable in the hottest months
    Presence of parasites: the lemon suffers from attacks by aphids and cochineal, animal parasites that feed on the sap flowing in the branches and leaves. In case of yellowing of the leaves, it is necessary to carefully observe the inside of the plant and the underlying part of the leaves because the parasites because that is where these enemies usually nest.
     
  5. scilover

    scilover Member

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    Sap-sucking insects can cause harm sufficient to clears out that they create yellow spots that inevitably develop together to create huge yellow patches. Check the undersides of the takes off and stems for the particular parasite included.
     
  6. Will B

    Will B Active Member

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    I would recommend getting a magnifying glass and looking really closely. To me it looks like you have signs of an early spider mite infestation. Spider mites are extremely small and hard to see, but they can cause the type of yellowing you are seeing. I can't quite tell for sure from the photos, but a few tiny bumps in one of the photos look suspiciously like spider mites to me. Once the infestation gets really bad you will see webbing and stippling on the leaves, but when it is just getting started it looks like your photos. My guess is they will be two-spotted spider mites. Here is some info on spider mites: Citrus: Identifying Spider Mites—UC IPM

    If you do have spider mites then there are various ways to control them. One way is to simply give the plant a good shower in your bathroom shower, making sure to spray the under side of the leaves if you can. This will reduce the damage and population considerably. A more effective method (but potentially messier) is to spray with oil. Oil will suffocate the mites. I tend to use horticultural oil when needed, 2 tablespoons per gallon of water, but other oils should work (like canola oil used in cooking) though I have not tried them.
     

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