Bonsai care (diseases and pests)

Diseases and pests

Like all garden or indoor plants, bonsai can suffer from diseases and be attacked by various harmful insects. Monitoring the condition of the plant is a daily concern for bonsai enthusiasts, especially during spring and summer. During this period, pests become more active, and the risk of plant damage from diseases increases significantly. Constant attention is necessary to prevent pests or diseases from causing irreversible harm to the plant.
The primary cause of plant diseases is improper care:

• Unsuitable location
• Insufficient or excessive watering,
• Excessive or insufficient fertilization,
• Incorrectly selected soil mix,
• Poor drainage,
• Strong wind.

If you follow all the proper care guidelines and the plant still becomes diseased, remember that a well-maintained bonsai is more resilient to stress than a neglected, weakened plant. The first signs of disease appear on leaves and needles. Regularly inspect both sides of the leaves. Symptoms include color changes, curling, spots, white coatings, sticky residues, and edge discoloration. Combat diseases and pests with specific chemical treatments, determined by the damage's cause. Immediate action prevents irreversible harm. Remove and burn damaged leaves, isolate affected plants, and maintain vigilance.

 Diseases

Powdery Mildew
Powdery mildew is a fungal disease caused by powdery fungi, developing on plants from early summer. It manifests as a grayish powder on leaves, shoots, and fruits. Leaves prematurely yellow and fall, while fruits harden and crack. The infection often begins on leaves closest to the soil and spreads to the entire plant.

Rust
Rust is a disease caused by fungi. Symptoms include small rust-colored spots developing on leaves. Infected plants experience disruptions in nutrient metabolism, water balance, and reduced photosynthesis efficiency.

Chlorosis
Chlorosis disrupts the production of chlorophyll, significantly reducing photosynthesis activity. As a result:
Leaf edges curl,

• The leaves partially or completely lose their green color,
• The leaves fall prematurely,
• New leaves grow smaller in size,
• The plant's growth slows down.

The cause of the disease can be either infectious or non-infectious in nature. Infectious chlorosis is caused by viruses, fungi, and other microorganisms, often transmitted by pests (mites and aphids).
Non-infectious chlorosis can be triggered by:

• Incorrect watering,
• Insufficient lighting,
• Inappropriate air humidity for the plant, 
• Lack of certain elements in the soil (iron, magnesium).

Verticilliosis
Verticilliosis is a disease that affects the tree's vascular system and causes wilting. The fungus *Verticillium* enters the plant through damaged roots and can dry out the tree within a few days. Initially, the leaves at the lower part of the tree turn yellow but do not fall off. The same happens to the rest of the leaves, and branches begin to weaken. To prevent verticilliosis, it is important to follow basic guidelines: do not overwater the bonsai, avoid excessive nitrogen fertilizer, and do not damage the roots during repotting.

Root Rot
The most difficult to detect is root damage, as it is impossible to monitor the roots on a daily basis. Root inspection is only possible during repotting. Therefore, damage is typically detected only after the process has advanced. During repotting, carefully examine the roots. Damaged roots are dark and break easily. Any decayed or broken roots must be trimmed with sharp scissors. The soil must be clean, free of pests and insects. Drainage holes must be checked. Water accumulation in the container is the main cause of root rot.

Pests

Pests are very small parasitic insects that feed on a plant's leaves or its sap. Primarily, these are various types of bugs and mites, which are so small that they are practically impossible to see without a magnifying glass.

Spider Mite
This microscopic parasite, measuring 0.5mm, resides on the underside of leaves. It spins a very fine web on the plant. It lays up to ten eggs a day, which are attached to the web. Spider mites feed on the leaf surface, sucking out cell contents. Their salivary glands release an extract that damages chloroplasts (the cells where photosynthesis occurs). Initially, reddish spots appear on the leaves, followed by darkening, premature drying, and leaf drop. In cases of mass reproduction, the plant dies.

Aphids
Aphids are the most common pests that damage both deciduous and coniferous plants. They range in size from 0.5mm to 6mm. They reproduce very quickly, up to twenty times a year. Aphids leave a specific shiny, sweet secretion on the leaves, which becomes noticeable after close inspection. Aphids feed on the plant, especially newly sprouted shoots. If not treated in time, they can ruin the decorative appearance of the bonsai and cause it to dry out.
On coniferous plants, you may notice white, flaky deposits. These are one type of aphid. They reproduce very rapidly and can dry out the plant completely in one season.

Millipede
   The millipede, due to its size, is easier to spot than mites or aphids. The first signs of damage include:

• Holes on the leaves,
• Eaten leaf edges,
• Conically curled leaves, which are used by the millipede as a "nest."

Ant
   Ants are carriers of various diseases. If you notice a large number of ants near the place where your bonsai is kept, use chemical agents to remove them.
Protecting the plant from diseases and pests is quite a difficult task for a non-specialist. First of all, diagnosing the problem correctly is not always easy, and the chemical solutions that treat certain diseases and eliminate pests change from year to year. The list of pests and diseases mentioned above is, of course, incomplete. Different types of plants are affected by different kinds of diseases. Therefore, it is important not to neglect the plant. If you notice any suspicious symptoms, immediately consult a specialist who will recommend a plant protection chemical and carefully follow their recommendations.