The lemon plant is an evergreen plant belonging to the Rutaceae family, native to East Asia and introduced to the Mediterranean area by the Arabs around 1000: pleasant to look at, easily recognizable, and highly appreciated for the production of its tasty fruits, if looked after with the right care and awareness it can become an absolute protagonist of our gardens for several decades.
However, even this plant is certainly not immune to diseases that can challenge its survival.
It is worth recalling, for example, how the lemon tree is particularly susceptible to some specific diseases that need to be identified early so that their rooting does not cast doubt on the very life of the plant. For example, as we will see more clearly in the next few lines, the difficulties can be traced to three major hypotheses:
- Fungal diseases: these are one of the most dangerous threats. Among the best known is fumaggine, recognizable by the presence of a dark patina on the leaves, such that photosynthesis is impaired. Also included in this category is dry rot, which causes progressive desiccation of branches;
- pests: mealybug is one of the most common enemies, but mites-and especially the red spider mite-are also capable of causing significant damage to one’s plants;
- physiological deficiencies and disorders: these are conditions often related to unfavorable environments or poor cultivation practices. Among them is ferric chlorosis, which manifests as progressive yellowing of leaves.
Lemon disease: how to tell that the plant is suffering
Each lemon plant disease has different symptoms, evolution and treatments. However, there are some common telltale signs that can lend us a hand in intercepting distressed conditions and, therefore, form the ideal basis for a right diagnosis.
The first and most recognizable symptom is certainly the failure to produce lemons: if the plant is no longer able to produce flowers or fruit, it is a sure wake-up call that should prompt more attention.
Another particularly important sign is the deterioration of the bark: if it begins to spoil, it is probably because an infection or other condition that is undermining the plant’s survival is in progress. The same can well be said for falling leaves: if the phenomenon is particularly intense, frequent, and numerous, it could be a telltale sign of an already entrenched disease. The presence of mold-usually in the lower part of the plant-is also another indicator of the poor health of the lemon plant.
For these very reasons, to keep the plant healthy we recommend:
- Make frequent and regular inspections of leaves, branches and fruit
- Ensure proper irrigation, avoiding water stagnation
- Ensure good air circulation through appropriate pruning
- Intervene in a timely manner at the first signs of disease with specific treatments
- Maintain proper nutrient balance through appropriate fertilization.
It thus emerges, again, how prevention is the best defense strategy against diseases in the lemon plant: well-cared-for and conscious maintenance, supported by our unique ecosystem, will in fact allow the plant to develop greater resistance to diseases, ensuring abundant and consistent production of its healthy and tasty fruits.
The main diseases of the lemon plant
As we introduced in the opening of this in-depth discussion, lemon plant diseases can pose a serious threat to the health and survival of this citrus fruit.
So let’s look at the most common diseases that can affect the lemon plant, from fungal problems to bacterial infections. For each disease, we will briefly review the characteristic symptoms and the most effective intervention strategies, providing practical guidance for both prevention and treatment.
Collar rot
The first lemon plant disease we want to deal with is collar rot, determined by fungi of the genus Phytophtora, the presence of which promotes the formation of wet spots on the bark at the base of the trunk.
In turn, gummy exudates emerge from the damp patches, which can quickly spread to affect the roots. The foliage and leaves begin to decay and yellow, the flowers become sparser, and the fruits become smaller, softer, covered with mold, and foul smelling. In severe cases, lesions with gummosis can affect the entire circumference of the trunk, leading the plant to death.
Given that the disease is favored by moisture stagnation at the collar of plants, an effective preventive measure is to smear trunk paste on the stems of plants during the winter season: since it is a compound with disinfectant action, it can ward off the spread of the fungi responsible for collar disease.
If, on the other hand, the infestation has already affected our plant, the trunk can be brushed with a copper product, appropriately diluted in water. If the case occurs, you can also spray the same product on the crown. As for the fruits, those affected and fallen to the ground should be removed in order to avoid sites of accumulation of the pathogenic element.
Dry sickness
Another lemon plant disease is dry rot, brought about by the fungus Phoma tracheiphilus, which contributes to yellowing of the leaves of the branches starting with the outermost ones. In some cases, however, the infection may start from the roots. Whatever the origin of the infection, unfortunately, the outcome does not change: the plant is doomed to a quick death if remedies are not taken immediately.
In particular, when the first symptoms are recognized on leaves and twigs, the parts must necessarily be removed, cutting below the visible symptoms, and then helping with copper. Cutting tools should then always be well disinfected. If the plant has died of this disease, it is important to disinfect the hole with lime and sulfur after levelling it.
Even for that scenario, to prevent infection , log paste can be of good help.
Bacteriosis
Additional lemon plant disease that should be taken care of is Pseudomonas syringae bacteriosis, which is visually recognizable because the action of the bacterium results in the onset of red-brown spots, from which gummy drop-like exudates may emerge.
The infection starts on the twigs and can reach the leaves, causing them to crumple. On fruits, however, the action of the ongoing infection can be recognized by the presence of spots about 1 cm in diameter with bacterial exudates.
As we commented above, this disease can also be addressed by copper treatments. Preventive action can be taken by spraying propolis.
Citrus tristeza virus
Citrus tristeza virus, or sadness virus, is one of the most dangerous diseases affecting lemon plants, responsible for millions of dead trees each year.
The evolution of the disease is unfortunately well known. Initially, the plant affected by this virus slows down its ordinary growth. However, the most common symbol is the one immediately following: the leaves turn yellow from the veins and, within a short distance, begin to fall off. The plant tries to respond with new shoots, but these remain small and light green in color. In case the virus starts from the roots, then it will soon attack the stem as well, damaging the water absorption capacity.
Given that the vehicles of the virus are aphids, the fight against this lemon plant disease must be conducted on them. Plants that have died from the virus must be uprooted and burned. Pits must be disinfected with lime.
Serpentine miner
Another relatively common problem among lemon plants is that of serpentine miner(Phyllocnistis citrella): the leaves thin and bleach before being darkened in a curvilinear pattern that appears to be embroidery. Finally, the leaves curl up and become sticky.
Treatment generally involves treating with Neem oil every 7-10 days until the pest disappears. However, if the problem is larger and involves more plants, it may be useful to install pheromone traps and, in more intense cases, spray the leaves with mineral oil.
Smoke
Although not a lemon plant disease in the strict sense of the word, fumigation is nonetheless often cited among the most troublesome conditions for the health of the tree.The condition is brought on by the presence of a saprophytic fungus that does not directly infect the leaves, but attaches itself to the honeydew honeydew of aleurodid aphids and mealybugs. The result is that the leaves reduce photosynthesis, facilitating the decay of the plant.
To defend against this condition, it is best to act directly on the insects that smear the plant with honeydew, through a treatment with Marseille soap on aphids.
Pests: mites, spider mites, mealybugs and larvae
Speaking of unwelcome presences on the lemon tree, it is worth mentioning some insects that could put a strain on the health of the plant.
Particularly when the plant is grown in very hot environments with stagnant air, it is certainly not uncommon for the dreaded red spider mite to find a home, which can usually be recognized by a punctiform discoloration of the leaves, which tend to be shrouded in thin webs. To discourage red spider mite infestation, it is a good idea to create a climate that is hostile to the insect by increasing humidity (which also works as a preventive factor), such as by steaming the foliage daily and moving the plant-if potted-to an airy spot. Should the spider webs appear more tenaciously, and not disappear within a week, they can be treated with soft soap, agrarian soybean oil or agrarian linseed oil.
On the other hand, if the lemon plant is affected by scale insects, the plant can be treated with mineral oil if the plant has no flowers, or with repeated treatments with soft soap if it also has flowers.
Finally, among the unwelcome presences on the lemon plant is the undermining larva, a butterfly that deposits its eggs inside the leaf page. Once hatched, the larvae will create labyrinths between the lower and upper leaf page. To treat the problem, one of the most effective products is rock dust.
The shortcomings
Among the most common problematic conditions for lemon plants is deficiency of key nutrients. For example, one can fall into this category is chlorosis, a situation in which the plant is no longer able to absorb sufficient iron or magnesium to meet its ordinary needs. The most immediate symptom of such a scenario is yellowed leaves, with only the veins tending to remain green.
If this case recurs, you can improve the health of the plant by supplementing the soil with a mineral fertilizer specifically for citrus, which contains additional doses of iron and magnesium. Simply follow the doses and frequency indicated on the label until the leaves have turned green again.
Another deficiency that can affect the lemon plant is that ofnitrogen: in this case, the leaves appear small in size and with a coloration that tends to turn yellow-orange. In case of persistence of this deficiency, the leaves necrotize starting from the edges, beginning with the lowest leaves and then continuing with those positioned in the highest part of the plant. Supplementation with a specific product is generally able to restore the tree’s healthy condition within a reasonable time.
| Pathology/Problem | Agent or Cause | Main Symptoms | Treatment/Prevention |
|---|---|---|---|
| Collar rot | Fungi of the genus Phytophtora | Moist spots on bark at base of trunk, gummy exudates, leaf yellowing, reduction of flowers and fruit, small and moldy fruit | Spreading winter trunk paste, treatments with copper products (on trunk and crown), removal of fallen fruit to prevent spread of the pathogen |
| Dry mal | Phoma tracheiphilus | Yellowing of leaves on outer branches (or departure from roots), progressive desiccation, rapid death if not promptly intervened | Removal of infected parts (cutting below symptoms), use of copper, disinfection of tools; in case of dead plant, disinfect the hole with lime and sulfur |
| Bacteriosis | Pseudomonas syringae | Red-brown spots on twigs and leaves, drop-shaped gummy exudates, spots about 1 cm on fruit | Copper treatments and, as a preventive measure, spraying with propolis |
| Citrus tristeza virus | Virus (mainly transmitted by aphids) | Slowing of growth, yellowing of leaves from the veins, leaf drop, small and weak new shoots | Removal and destruction of infected plants, strict control of aphids and disinfection of pits |
| Serpentine miner | Mining insect(Phyllocnistis citrella). | Thinning and bleaching of leaves, formation of curvilinear (embroidery-like) patterns, leaves becoming sticky | Treatment with Neem oil every 7-10 days, installation of pheromone traps and, in case of extensive infestations, spraying with mineral oil |
| Honeydew | Saprophytic fungi that develop on honeydew produced by insects | Formation of a dark patina on leaves that reduces photosynthetic activity | Control of insects (aphids, aleurodids, mealybugs) with Marseille soap treatments to eliminate the source of honeydew |
| Pests (Mites and Red spider mite) | Insects such as red spider mite and other mites. | Punctate discoloration of leaves, presence of thin spider webs, possible general weakening of the plant | Improve air circulation, increase humidity (daily steaming), and targeted treatments with soft soap or agrarian oils (soy/linseed) in case of persistent infestations |
| Cochineal | Parasitic insect | Sticky secretions, yellowing and deterioration of leaves, possible reduction in plant viability | On plants without flowers, apply mineral oil; if in flower, prefer repeated treatments with soft soap |
| Ferric chlorosis | Iron and magnesium deficiency (often related to unfavorable cultural practices or soil) | Yellowed leaves with veins still green | Supplementing the soil with a citrus-specific mineral fertilizer containing extra doses of iron and magnesium |
| Nitrogen deficiency | Nitrogen deficiency in the soil | Reduced leaves, yellow-orange coloration, necrosis starting from the edges, especially in lower leaves | Use of specific high-nitrogen fertilizers following recommended doses |
Adopting a preventive approach and accurate diagnosis is crucial to keeping the lemon tree healthy. Taking timely action against diseases and pests not only preserves the vitality of the tree, but also ensures consistent, quality production.
Specialized tools and resources, such as those offered by PlantVoice, provide valuable support in monitoring the state of the plant and applying the correct intervention techniques. Focusing on preventive care, in fact, means investing in the well-being of our citrus tree, ensuring its longevity and yield in every season.
