Tobacco, potato, cabbage, geranium black shank disease what are the symptoms? What drugs?

Black shank is a bacterial disease that overwinters on plant residues in the soil or on diseased tubers during storage, but it does not remain in the soil for long. It occurs on tobacco, potatoes, cabbage, cabbage, geranium and other crops. What are the symptoms of black shank? What drugs?

potato black shank

Potato black shank is a bacterial disease infecting vascular tissue. It can occur in the whole growth cycle of potato. Warm and humid is conducive to the invasion of the pathogen, especially in rainy years, low-lying areas, potato black shank damage is more serious.

symptoms

Seed potato: infected seed potato rot into sticky mass, do not germinate, or just germinate that rotted in the soil, can not emerge.

Seedlings: infected seedlings generally 15~18cm high symptoms, plant short, internode shortening, or leaf roll up, chlorosis, or shank black, wilting and death. Three main vascular bundles were seen in transverse section of stem turning brown.

Field potato pieces: infected potato pieces start from the umbilicus, radially expand to the pith, the diseased part is black-brown, the vascular bundle is also black-brown in cross section, the skin is not separated by hand compression, when the humidity is high, the potato pieces become black-brown, rotten and smelly, different from bacterial wilt.

Transmission routes and rules

Seed potato transmission: seed potato with bacteria, soil generally not bacteria. Cutter-knife infection is the main way of disease transmission during potato cutting. The pathogen first spread through potato cutting, causing more seed potato disease, and then entered the plant through vascular bundle or pith, causing aboveground disease.

Field transmission: field germs can be transmitted by irrigation water, rain or insects, invaded by wounds, and the germs on the later diseased plants are transmitted from the stems to the newly grown tubers through stolons.

Storage spread: Pathogens infected healthy potatoes by contact with diseased potatoes through wounds or perforations during storage.

morphological characteristics

Potato black shank disease belongs to bacterial disease. The pathogen belongs to Euclidean bacillus. The thallus is short rod shape, round at both ends, with 4-5 flagella, no spore and negative gram stain reaction. Colonies on agar medium are pale white and round. The pathogen can grow well in the range of 10-38℃, the optimum temperature is 25 - 27℃, and loses its vitality above 45℃.

control methods

(1) Selection of resistant varieties.

(2) Select disease-free seed potato to establish disease-free remaining field.

(3) Cut potatoes with a knife in time alcohol or potassium permanganate sterilization, cut into pieces with rice or color long dressing seeds, dry immediately after sowing.

(4) Early sowing in due time, paying attention to drainage, reducing soil moisture, increasing ground temperature and promoting early emergence.

(5) Seed potatoes should be strictly selected before entering the cellar, and management should be strengthened after entering the cellar. The cellar temperature should be controlled at 1-4℃ to prevent the cellar temperature from being too high and humidity too high.

(6) Chemical control:

After seedling emergence, 100ml leaf spray of rice or color long was used for prevention; 300ml root irrigation of rice or color long was used for drip irrigation and 500ml root irrigation for sprinkler irrigation at the early stage of disease. In the middle and late stages of disease, drip irrigation and irrigation were 200g/mu and 300g/mu respectively.

tobacco black shank

symptoms

Black spots appeared on roots and stems near the ground, and the diseased parts extended up and down to all stems, leaves and taproots. Infected stem base thin constriction, easy to cause damping-off. In high humidity and heavy rain, all the diseased seedlings rot, white pilose mold is produced on the surface, and quickly spreads to nearby seedlings, causing tobacco seedlings to rot and die. If the weather is dry, the diseased seedlings dry up and appear dark brown. When the seedlings are slightly infected, the symptoms are not obvious. Tobacco seedlings transplanted into the field, encountered high temperature and humidity environment, easy to disease. Most of them begin to blacken near the ground at the root intersection, and expand upward, often up to 0.6 ~1 feet, so they are called black shank disease. Sometimes the disease blackens in the middle of the stem, causing the tobacco plant to die; sometimes the stem does not present disease spots and withers and dies, pulling up the diseased plant, you can see the taproot and branch root blackening and rotting. Although the disease has a variety of symptoms, but the common feature is that the leaves of the infected plants are gradually yellow and drooping from bottom to top. At the initial stage of the disease, they can recover after night. After 4 - 5 days, all leaves wither, and finally the whole plant dies. The diseased plants are easy to pull up because most of the fine roots are rotten. In addition to the cortex turning black, the pith of the damaged stem also turned black and brown, and dried up and contracted into laminated sheets, with sparse white mold between the sheets. In case of rainy and humid weather, white mold is also produced on the appearance of diseased tissues.

control methods

1. Selection and cultivation of disease-resistant varieties

2. To strengthen cultivation management, spring tobacco should be developed and transplanted early so as to avoid rainy season in infection stage. implement rotation for more than three year; ridging and cultivate soil, ditching and draining to ensure that there is no ponding in tobacco fields and no "excessive water"; after ridging, running water on that ground does not contact the base of stems to reduce the chance of infection; applying clean fertilizer to keep running water from being contaminated by germs; and removing diseased plants and picking diseased leaves should be treated in a centralized manner.

3. Chemical control was based on the three characteristics of black shank pathogen: moving spores in the topsoil for reinfection, mainly attacking the base of stem, and infection stage after transplanting and before budding. Generally, more than 60% control effect could be obtained. This is especially necessary for some varieties with good quality and poor disease resistance. Dixone can be used, the application amount is 7 liang per mu, mixed with 30~40 jin of dry fine soil, applied once before sealing and ridging, scattered around the tobacco plant, and immediately restored to avoid the failure of dixone in light.

black shank of cabbage

Most occur in high temperature, high humidity areas and seasons, seedling and adult stage can be damaged, serious cause dead plants. Besides cabbage, cabbage, rape, cauliflower, turnip, radish, cabbage, Chinese kale and celery are also harmed by this disease.

symptoms

Light brown spots were produced on cotyledons, true leaves and young stems at seedling stage, round or oval spots, scattered black dots on them, spots on young stems were slightly depressed, and seriously ill seedlings died quickly. The leaf spots in adult stage are the same as those in seedling stage, and purple-black stripes are produced on the lateral roots of taproot, which makes the roots rot or fold down from the diseased stems.

control methods

Seed treatment: Soak seeds in warm water at 50℃ for 20 minutes. Seed dressing: seed dressing with 50% thiram wettable powder, the weight of the agent is 0.4% of the weight of the seed. Soil treatment: use 40% thiram wettable powder or 40% pentachloronitrobenzene powder, mix 30~40 kg fine dry soil according to 8~10 g of pesticide per square meter, and sprinkle on the bed surface when sowing. Cropping rotation: the field with heavy disease should be changed in time or rotated with non-cruciate vegetables, and the rotation with field crops is better, with an interval of more than 3 years. Chemical control: spraying at the early stage of disease, spraying 75% chlorothalonil wettable powder 600 times solution, or 40% polysulfide suspension 600 times solution, or 60% Duofu wettable powder 600 times solution, etc., spraying once every 8~10 days, spraying twice continuously.

Pelargonium black shank

symptoms

The disease occurs on both cuttings and mature plants, but the cuttings are more severely damaged, starting from the base of the stem to rot and develop upwards, causing death. After the disease, the adult plants turn black and expand upward, and the leaves fall off, so that they wither and die.

pathogenic

Pythium ornate, belongs to the subphylum flagellates. Hyphae developed, branched, no septa, growth exuberant when white cotton flocculent. The sporangia are filiform, rounded or subrounded, producing zoospores that cause infection.

control methods

1, cuttage must be cut on the branches of healthy plants, and must be cuttage in the seedbed without pathogens.

2. When transplanting, it is necessary to change the new lot or replace the pot soil to prevent infectious diseases. When necessary, 70% Dixon WP 1000-1500 times solution can be poured on the soil surface.

broccoli black shank

[Symptoms] Also known as root rot disease, black root disease, etc., seedling stage, adult stage can be affected. The cotyledons, true leaves or young stems of infected seedlings can appear gray irregular spots, the base of the stem infected spread to the roots, forming black-purple strip spots, the stem base ulcer is serious, the infected plants are easy to break and dry; the infected leaves of adult plants produce irregular to angular gray spots, on which many black small dots are born, i.e. the conidia of the pathogen; the pedicels and seed pods are infected and similar to the stems; the infected leaf bulbs dry and rot during the storage period of the seed plants, and the vascular bundles of the infected roots turn black.