Control of main diseases in flower seedling stage

Spring is a favorable time for raising seedlings of many kinds of flowers, such as red, four seasons begonia, mallow and so on. However, due to the changeable climate in spring and the frequent occurrence of cold snap, it often brings favorable conditions for the occurrence of many kinds of diseases in flower seedling stage. The occurrence and control methods of main diseases in spring flower seedling stage are introduced as follows.

The seedlings unearthed or newly unearthed can get sick and the germs and cotyledons rot when the seedlings are not unearthed. When the unearthed seedlings fell ill, water-immersed disease spots appeared at the base of the young stems, and then the diseased parts became yellowish brown, dried and thinned, and the seedlings were broken as soon as they were pulled out. When the disease occurred on the seedbed, only a few seedlings occurred at the beginning, and a few days later, it spread rapidly to the neighboring plants, causing a piece of seedlings to collapse. When the humidity is high, a layer of white cotton-like mycelium grows on the host disease and the surrounding soil. The pathogen overwintered in the soil in the form of oospores and germinated under suitable conditions to produce zoospores or directly grow germ tubes to invade the host. Germs are spread by Rain Water or the flow of water in the soil. There are many bacteria in seeds and bed soil, and the seedlings are more susceptible to disease. The plant is prone to disease due to low ground temperature, high humidity of seedling bed and lack of light. Herbaceous flowers such as impatiens, cockscomb and other herbaceous flowers that sow and raise seedlings are frequently affected and seriously injured.

Prevention and cure method

1. Choose the seedling bed. The nursery land should choose the soil with higher topography, good drainage, loose and fertile soil, good ventilation and uncultivated susceptible flowers as bed soil.

2. Disinfect the bed soil. The medicinal soil was prepared with 7 to 8 grams of 65% zinc and 50% carbendazim per square meter, or 5 grams of 70% dimethazone and 15 kilograms of dry fine soil. When sowing, the first one of the medicinal soil was used as a cushion, and then the second one of the medicinal soil was used as a cover after sowing.

3. Seed disinfection. Sun the seeds for 1 to 2 days before sowing, and then soak the seeds with 50% carbendazim 250 times solution for 24 hours. It can kill the germs on the seeds.

4. Chemical control. At the beginning of the disease of the seedlings, the diseased plants can be irrigated with 1000 times of 80% bacillus, or sprayed with 1000 times of 25% redox, once every 7 days, twice continuously, which can effectively control the spread of the disease.

Root rot mainly harms seedlings and can also occur at adult stage. At the initial stage of the disease, only individual branch roots and whisker roots were infected, and gradually extended to the main root. after the main root was infected, the early plant showed no symptoms, and then the function of absorbing water and nutrients gradually weakened with the aggravation of the degree of root rot. the aboveground part was in short supply of nutrients, the upper leaves of the plant wilted only when the light was strong and the evaporation was large around noon, but recovered at night. When the disease is serious, the wilting condition can not recover at night. At this time, the root bark turned brown and separated from the pith, and finally the whole plant died. The disease is often similar to retting root symptoms and belongs to fungal disease. The pathogen spent the winter in the soil and on the diseased body, usually from late March to early April, and entered the peak period in May, and its occurrence was closely related to the climatic conditions. Low temperature and high humidity of seedling bed and lack of light are the main environmental conditions that cause the disease. The growth and development of root system is hindered due to the high viscosity, easy consolidation and poor ventilation of the soil, and the disease is also easy to occur. In addition, after the roots are harmed by underground pests and nematodes, there are many wounds, which is beneficial to the invasion of bacteria. In this environment, not only the herbaceous flowers of sowing and cutting are vulnerable, but also the woody flowers such as rose, hibiscus and mulberry are also easy to occur.

Prevention and cure method

1. Disinfect seeds and cuttings. Before sowing, the seeds can be mixed with 0.3% of seed weight or 0.1% of seed weight, or soaked in 2000 times of 80% antibacterial agent EC for 5 hours; the base of cuttings can also be soaked in the same concentration for 1 hour before cutting.

2. Seedbed soil disinfection, 1.5 grams per square meter of carbendazim scattered on the surface into the soil, or 75% pentachloronitrobenzene 3 grams have a good effect, and can also treat quenching disease, blight disease.

3. Chemical control. When the disease occurs, the diseased plant can be sprayed or irrigated with 1000 times of 40% Gen Fu Ning, or 1500 times of 80% EC.

4. Control the harm of underground pests and nematodes in time.

The white silk disease was mainly damaged at the base of the stem of the seedlings. at the beginning, the stem near the root appeared water-stained brown irregular spots, the cortex was soft rot, and then expanded around the base of the stem, producing white silk-like mycelium on the surface. and can spread to the surrounding soil to form a layer of white silk-like omentum. After that, the mycelium gradually gathered into many small white granules, then gradually changed into light yellow, yellow, light brown, and finally turned into brown rapeseed sclerotia. In the later stage of the disease, the stem base and the whole root system decayed and died. The pathogen overwinters with sclerotia or mycelium in the soil or in the remnant of the diseased plant. The hyphae were produced in the following spring for infection. Soil fertilizer mixed with diseased and residual tissue can also spread the disease. Repeated infection between nurseries (beds) is spread by mycelium expansion, contact of diseased and healthy plants, running water, management and operation; if diseased plants appear in the field, the hyphae in the soil around diseased plants can spread to adjacent plants along soil cracks or the ground. The hyphae generally invade directly from the base of the stem of the host, and are more likely to invade from the stem wound. The occurrence of disease is closely related to temperature, humidity and pH value. High temperature and humidity, over-acid soil, over-dense plants, poor ventilation and light transmission are conducive to the disease. The survey found that impatiens, orchids, peonies, magnolia, chrysanthemums, peony, evergreen, irises, Ruixiang, jasmine and other flowers are vulnerable.

Prevention and cure method

1. Soil disinfection. No matter it is potted or planted on the ground, the soil should be disinfected. Use 1.5 grams of agricultural emulsion per square meter to mix 25 kilograms of fine soil and spread it into the soil.

2. At the initial stage of the disease, 75% pentachloronitrobenzene 0.5kg and fine soil 20kg were mixed into medicinal soil and sprinkled on the ground around the base of the stem, or sprayed with 45% Dysenamine 800x solution on the base of the plant and its surrounding soil, or 2000 times solution of 25% strychnine was used to irrigate the diseased plants. can effectively control the occurrence and spread of the disease.