How to prevent and treat stem base rot in Japanese holly?

Japanese holly is mainly distributed from the lower reaches of the Yangtze River to parts of South China, East China, and North China, with production areas mainly concentrated in Hunan, Zhejiang, Fujian, and Jiangsu. It prefers a warm, humid environment with plenty of sunlight, tolerates partial shade, and can be grown for ornamental purposes. Stem base rot is one of the main diseases harming Japanese holly, so what are the prevention and treatment methods for stem base rot in Japanese holly?

I. Symptoms of stem base rot in Japanese holly

At the initial stage of the disease, irregular water-soaked patches appear on the stem base near the ground, light brown in color. The cortex of the diseased area becomes soft, water-soaked, and easy to peel off, with an unusual odor when smelled closely. The diseased area gradually expands around the entire stem base and darkens in color. Later, white granular substances grow on the diseased area. After onset, the upward transport of water and nutrients is affected, causing branches to wilt. As the disease worsens, the branches above the diseased area gradually dry up and die.

II. Prevention and treatment methods for stem base rot in Japanese holly

1. The planting site should be a gently sloping area with good ventilation and drainage. Strengthen cultivation management, prune diseased and dead branches as well as overly dense branches, use hedge-type or shed-type trellises to increase ventilation and light penetration within the garden, promptly remove severely diseased plants, and use quicklime to disinfect the soil.

2. Use Songda bio-organic fertilizer for soil improvement, and for overwintering old plants, after the temperature stabilizes above 12°C, uncover the soil around the root crown to slightly expose the root system, and sun the root crown to release the plants.

3. At the initial stage of the disease, use chemical control: first scrape the diseased spots on the stem base clean with a knife, then apply Guoguang Song'er at a 600-fold dilution to the stem base. At the same time, use Guoguang Genbao at a 2000-fold dilution + Guoguang Chongchabao at a 1500-fold dilution for root drenching, using about 500ml of solution per plant, drenching 1-2 times as needed.

III. Care tips for Japanese holly

1. Soil

Japanese holly is a highly adaptable tree species that can grow whether in sunny or shady conditions. It prefers moist, fertile, slightly acidic loess soil, and neutral soil also works.

2. Propagation

Japanese holly used for making bonsai is usually propagated by cuttings, generally carried out during the growing season from May to July. Cuttings can be taken from robust, well-developed branches of the previous year or the current year. Remove the lower leaves, place the cuttings in a bright location without direct sunlight for care, keep the soil and air moist, and they will root in about 50 days.

3. Watering

It prefers a warm, humid environment with plenty of sunlight and tolerates partial shade. During the growing season, keep the potting soil moist but not waterlogged. When the air is dry, mist the plant to keep the leaves glossy. Apply a dilute alum fertilizer solution once every 12-20 days to provide sufficient nutrients, keeping the leaves dark green and glossy and the plant full of vitality.

4. Pinching

Because Japanese holly has strong sprouting ability, timely pinching and tipping is needed. Remove excess new buds to maintain a beautiful tree shape.

5. Overwintering

In winter, it requires cool conditions and can be moved to a cold room for overwintering, maintaining a temperature above 0°C as long as the potting soil does not freeze. In areas south of the Yellow River, it can also overwinter outdoors in a wind-sheltered, sunny location. Water thoroughly once before overwintering and replenish water promptly to avoid the potting soil becoming too dry, which could cause freeze-drying, but also prevent waterlogging in the soil, which could cause root rot.