What are the control measures for soft rot in clivia?

Clivia belongs to the genus Clivia in the Amaryllidaceae family and is a perennial evergreen herbaceous flower. Since it was introduced into China from Japan in 1932, it has been commonly cultivated and planted in various regions of China. Clivia soft rot is a common disease of clivia, and after it occurs, it often causes the death of the entire plant and thus causes great economic losses. Disease control in clivia requires targeted measures for prevention and treatment according to its symptom characteristics.

I. Symptoms of soft rot

Soft rot mainly damages the pseudobulb and leaves of clivia. In the early stage of disease at the stem base, small water-soaked spots appear, which later gradually expand into light brown spots and spread to the pseudobulb, causing the tissue to rot, become soft and decayed, and emit a foul odor. The lesions at the stem base can also spread along the leaf veins to the leaves. In the early stage, the leaves show water-soaked spots, which then rapidly expand and become decayed and semi-transparent, with a yellow halo around the lesions and a broad band around the halo. In severe cases, the entire leaf rots and disintegrates into wet rot.

The pathogen of this disease is bacteria, mainly Erwinia chrysanthemi and Erwinia carotovora subsp. atroseptica of the genus Erwinia.

II. Disease occurrence pattern

The pathogenic bacteria overwinter in the soil or in diseased plant residues. The disease can occur from June to November, but mostly occurs during periods of high temperature and high humidity in summer. Poor ventilation favors the spread and development of the disease. The bacteria can survive in the soil for several months, and contaminated soil is an important source of infection. Therefore, incomplete soil disinfection can easily lead to the occurrence of this disease. In addition, it can also be spread by water flow, insects, contact and friction between diseased leaves and healthy leaves, or through operating tools. The bacteria invade the plant body through wounds and can cause disease within a few days, and can repeatedly infect during the growing season. In summer, if the stem core of clivia is exposed to rain or if water is accidentally poured into the stem core during watering, this disease can be induced. In addition to infecting clivia, this pathogen can also cause disease in chrysanthemum, dianthus, dahlia, begonia, rohdea and others.

III. Control of soft rot

1. Soil disinfection: In order to prevent soft rot in advance, disinfect the potting soil before transplanting. The soil can be disinfected with 0.5%-1% formalin, about 10 g per square meter; it can also be disinfected with chloropicrin at 60-120 g/sq m or 70% quintozene at 8-10 g/sq m.

Used flower pots and contaminated tools should also be cleaned and disinfected with 1% copper sulfate before use. Usually, do not water too much to avoid excessive moisture in the potting soil.

2. Agricultural control: Promptly prune or pull out diseased plants and destroy them; do not bruise the plants when planting and transplanting, so as to avoid wound infection; during the disease period, pay attention to drainage and keep the rhizomes dry, so as to avoid rot of the roots, rhizomes and bulbs.

3. Chemical control: After the disease occurs, spraying agricultural streptomycin at 1000 times dilution or Bordeaux mixture at 150-200 times dilution about once every month can control the spread of the disease. At the same time, when insect pests are found, they should be controlled promptly to reduce wounds and lower the disease incidence.