Unfortunately, lemon trees are quite susceptible to disease. These are mostly due to incorrect care or overwintering, but can also be caused by pest infestation. However, yellow leaves appearing on older shoots are normal. This can be prevented with regular fall pruning.
care mistakes
If the leaves of the lemon tree are turning yellow, it may be due to spider mites. However, if there is no pest infestation, you should assume a nutrient deficiency. There are various reasons for this:
- If roots are kept too moist for a long time, especially with bitter oranges as a grafting base and with cuttings, root rot can be the cause. Due to the defective roots, nutrients are no longer transported to the crown, and the leaves turn yellow.
- If the plant has been kept too dry during the growing season, nutrients will not be able to reach the crown as nutrients cannot be absorbed from dry soil.
- The plant has not yet been fertilized during the vegetation period or has only been insufficiently fertilized. A sufficient supply of nitrogen is mainly responsible for the lush green leaves.
- Watering with hard water also blocks the absorption of nutrients such as iron - especially with bitter lemon rootstocks. However, intensive iron fertilization is not recommended, as this often creates gum flow at the base of the stem, which can cause the death of the plant. In this case, it is better to immediately switch to lime-free irrigation water.
Damage caused by improper wintering
If your lemon tree loses many or even almost all leaves, this is usually due to a winter that was too warm and/or too dark. Another reason can be that the plant was once kept too dry, so that the leaves have already curled up at the outer edge. After subsequent watering, all foliage is often thrown off. If the drought damage was not too great, the lemon tree will usually sprout again.
pest infestation
Lemons are very often attacked by scale insects, aphids, mealybugs, mealybugs and spider mites. Sticky leaves and shoots always indicate an infestation with plant lice.
scale insects
The tiny scale insects are difficult to see with the naked eye. They sit on the underside of the leaves along the pathways and on young shoots. The lemon appears to be sticky due to the sticky honeydew excretions, and the liquid also attracts ants. In addition, the sooty mold fungus likes to settle on the honeydew, which covers the leaves black.
aphids
An aphid infestation can be recognized from afar by the stunted shoots and twisted leaves. The animals prefer to stay on soft new shoots.
Mealybugs and mealybugs
The white to pink-colored mealybugs and mealybugs can usually be found on the undersides of the leaves, in the leaf axils and in the tips of the shoots. They are about twice the size of scale insects, making them easier to spot.
spider mites
Like plant lice, spider mites also belong to the pests that suck plant sap. An infestation can be recognized by light spots on the underside of the leaves, with severe infestation webs form there and in the leaf axils. Spider mites can usually be kept in check by high humidity.
tips and tricks
You can counteract a pest infestation by dipping the lemon tree upside down in soapy water and leaving it that way for a while. However, the substrate must not get any soap, and the treatment must be repeated several times.