The primrose is a perennial herb of the primrose family, which contains many species of winter and spring flowering. The plant can produce a large number of beautiful flowers. The flowers are clustered in the center of the leaves and the flowers are very rich. The author now introduces the common diseases of primrose as follows.
First, primrose mosaic disease
Symptoms: Whole-plant disease caused by cucumber mosaic virus CMV. Symptoms are small, deformed leaves with dark green markings or yellowing. The infected plants do not flower or flower, and the flowers are short and deformed with streaks (see Figure 1). The route of infection is mainly transmitted by peach aphid and cotton aphid. The main source of infection is the surrounding weed susceptible strain.
Control methods: First, weeds should be removed in time to reduce the source of infection. Secondly, we should control mites early and eliminate the transmission of drugs.
Second, primrose brown spot disease
Symptoms: Most occur in the spring season. It is caused by the Alternaria species of the subgenus. The infected plants have brown spots on the leaves. The route of infection is that conidia spread by wind and rain.
Control method: Spray 70% chlorothalonil WP 1000 times liquid and other fungicides at the beginning of the disease.
Third, primrose gray mold
Symptoms: One of the common diseases of primrose has occurred throughout the country. After the plant is susceptible, the whole plant is yellowed and dead. The disease mainly infects leaves, tender stems, flowers and other parts. More occurs at the tip of the leaf and at the edge of the leaf. At the beginning of the disease, the leaves showed water-soaked spots, which gradually expanded and became brown and spoiled. In the later stage, a gray-yellow mold layer was formed on the surface of the lesion. After the stem is susceptible, the lesion is brown and gradually rots. After the flower is infested, it also becomes brown and rots and falls off. In the wet conditions, the gray mold layer appears in the diseased part, which is a major feature of the disease. The disease is overwinter in the sclerotia and in the soil. When the temperature is around 20 °C and the humidity is high, it is easy to develop. Spread through wind and rain, tools, and irrigation water. The most serious disease occurs in the greenhouse in late winter and early spring.
Control method: Planting density should be reasonable. Pay attention to ventilation and reduce air humidity. Diseased leaves and diseased plants are cleared in time to reduce the source of infection. In the early stage of the disease, spray 50% keeling or 50% phorhin WP 1500 times. It is preferably applied alternately with 65% of the methicillin WP 500 times to prevent drug resistance.
Fourth, primrose spot disease
Symptoms: Mainly damage the leaves of plants. The condition spreads from the lower part of the plant to the upper part. The lesion is usually 3 to 4 mm in diameter, brown, and in severe cases, the diseased leaves die, causing defoliation (see Figure 2). The disease is caused by P. pyogenes. The pathogens overwinter on the diseased bodies by mycelium or conidia, and the seeds can also carry bacteria, which becomes the first source of infection in the second year. The disease mainly relies on conidia to spread with air and rain. Frequent infections during the growing season. Plants are prone to disease when they are usually warm and humid and when nitrogen is applied. It usually begins in July and is popular from August to October.
Control methods: Breeding resistant varieties, strengthening fertilizer and water management, adding organic fertilizer and phosphorus and potassium fertilizer to avoid partial application of nitrogen fertilizer. In the initial stage of the disease, spray 70% thiophanate-methyl 1000 times solution and 75% chlorothalonil WP 1000 times solution, or 1:1:100 Bordeaux mixture.
5. Primula flower leaf spot
Symptoms: More on the leaves and receptacles. In the initial stage, water-immersed irregular lesions are produced along the veins, and then yellowing and browning, the lesions are enlarged, and the leaf margins are dry. In severe cases, it will die from the lower leaves.
Control methods: strengthen cultivation management, cultivate disease-free seedlings, seedbed soil should be disinfected; greenhouses should be released in time to reduce air humidity. Timely removal of diseased plant residues. After the onset, 50% succinic acid copper WP 1500 times solution, or 72% agricultural streptomycin WP 4,000 times solution.
Six, primrose deficiency iron yellow leaf disease
Symptoms: The upper leaves of the plants first lose green, while the old leaves are still normal. The chlorosis leaves turn yellow and the veins remain green. In severe cases, brown spots appear on the tip of the leaf, and even fall off.
Control method: The soil should be made of iron-rich loam. The addition of ferrous sulfate, zinc sulfate, etc. to the organic fertilizer can promote root development and increase the ability to absorb iron. In the case of iron deficiency, spray 0.2 to 0.5% ferrous sulfate solution, the effect is better than direct application into the soil.
First, primrose mosaic disease
Symptoms: Whole-plant disease caused by cucumber mosaic virus CMV. Symptoms are small, deformed leaves with dark green markings or yellowing. The infected plants do not flower or flower, and the flowers are short and deformed with streaks (see Figure 1). The route of infection is mainly transmitted by peach aphid and cotton aphid. The main source of infection is the surrounding weed susceptible strain.
Control methods: First, weeds should be removed in time to reduce the source of infection. Secondly, we should control mites early and eliminate the transmission of drugs.
Second, primrose brown spot disease
Symptoms: Most occur in the spring season. It is caused by the Alternaria species of the subgenus. The infected plants have brown spots on the leaves. The route of infection is that conidia spread by wind and rain.
Control method: Spray 70% chlorothalonil WP 1000 times liquid and other fungicides at the beginning of the disease.
Third, primrose gray mold
Symptoms: One of the common diseases of primrose has occurred throughout the country. After the plant is susceptible, the whole plant is yellowed and dead. The disease mainly infects leaves, tender stems, flowers and other parts. More occurs at the tip of the leaf and at the edge of the leaf. At the beginning of the disease, the leaves showed water-soaked spots, which gradually expanded and became brown and spoiled. In the later stage, a gray-yellow mold layer was formed on the surface of the lesion. After the stem is susceptible, the lesion is brown and gradually rots. After the flower is infested, it also becomes brown and rots and falls off. In the wet conditions, the gray mold layer appears in the diseased part, which is a major feature of the disease. The disease is overwinter in the sclerotia and in the soil. When the temperature is around 20 °C and the humidity is high, it is easy to develop. Spread through wind and rain, tools, and irrigation water. The most serious disease occurs in the greenhouse in late winter and early spring.
Control method: Planting density should be reasonable. Pay attention to ventilation and reduce air humidity. Diseased leaves and diseased plants are cleared in time to reduce the source of infection. In the early stage of the disease, spray 50% keeling or 50% phorhin WP 1500 times. It is preferably applied alternately with 65% of the methicillin WP 500 times to prevent drug resistance.
Fourth, primrose spot disease
Symptoms: Mainly damage the leaves of plants. The condition spreads from the lower part of the plant to the upper part. The lesion is usually 3 to 4 mm in diameter, brown, and in severe cases, the diseased leaves die, causing defoliation (see Figure 2). The disease is caused by P. pyogenes. The pathogens overwinter on the diseased bodies by mycelium or conidia, and the seeds can also carry bacteria, which becomes the first source of infection in the second year. The disease mainly relies on conidia to spread with air and rain. Frequent infections during the growing season. Plants are prone to disease when they are usually warm and humid and when nitrogen is applied. It usually begins in July and is popular from August to October.
Control methods: Breeding resistant varieties, strengthening fertilizer and water management, adding organic fertilizer and phosphorus and potassium fertilizer to avoid partial application of nitrogen fertilizer. In the initial stage of the disease, spray 70% thiophanate-methyl 1000 times solution and 75% chlorothalonil WP 1000 times solution, or 1:1:100 Bordeaux mixture.
5. Primula flower leaf spot
Symptoms: More on the leaves and receptacles. In the initial stage, water-immersed irregular lesions are produced along the veins, and then yellowing and browning, the lesions are enlarged, and the leaf margins are dry. In severe cases, it will die from the lower leaves.
Control methods: strengthen cultivation management, cultivate disease-free seedlings, seedbed soil should be disinfected; greenhouses should be released in time to reduce air humidity. Timely removal of diseased plant residues. After the onset, 50% succinic acid copper WP 1500 times solution, or 72% agricultural streptomycin WP 4,000 times solution.
Six, primrose deficiency iron yellow leaf disease
Symptoms: The upper leaves of the plants first lose green, while the old leaves are still normal. The chlorosis leaves turn yellow and the veins remain green. In severe cases, brown spots appear on the tip of the leaf, and even fall off.
Control method: The soil should be made of iron-rich loam. The addition of ferrous sulfate, zinc sulfate, etc. to the organic fertilizer can promote root development and increase the ability to absorb iron. In the case of iron deficiency, spray 0.2 to 0.5% ferrous sulfate solution, the effect is better than direct application into the soil.
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