The disease of tomato late blight is believed that tomato growers will not be unfamiliar, mainly harming leaves and fruits, resulting in a 20%-30% reduction in production, and severe harvest. The following rigorous investigations by experts over the years, summing up the lessons learned, according to the different symptoms of the disease on the plant, fruit, tomato late blight prefers low temperature and damp conditions, the severity of the disease in spring, select effective chemical control measures.

1 Tomato late blight pathogen and its biological characteristics

1.1 pathogenic bacteria

Tomato late blight is a fungal disease caused by Phytophthora infestans, which is also a common disease in open fields and protected areas. This genus is a fungus of the genus Phytophthora. The mycelium is colorless, has no membrane, grows in the space of the host cell, and absorbs nutrients into the host cell with few filamentary absorbers. The white mold on the lesion is the spore stalk and sporangia of the pathogen. Conesium 3-5 plexus bundles, sometimes 10 large, extending from the stomata or diseased epidermis, linear non-branched, size 112-456um × 3-4um, more than 9-10. The conidia are colorless and transparent, pear-shaped or sage-like. Mature spores have 2-3 membranes, the size is 17-33um×6.5-11um. When germination, the cells at both ends produce germ tubes, and the tops of the germ tubes produce attached cells, spherical or elliptical, dark brown, wall thickness, diameter 8- 12um, intimidating on the host to invade the silk, invading the host organization.

1.2 Biological characteristics of pathogens

Appropriate temperature and humidity have a great effect on the pathogens. The optimal temperature for mycelial development is 24 °C, the relative humidity is higher than 91%; the optimal temperature for sporangia is 18 to 22 °C, and the optimum relative humidity is 100%. . Sporangia germination is closely related to temperature. The higher the temperature, the shorter the time required for sporangia to sprout. When the relative humidity is below 95%, the sporangia loses its vitality immediately. It has been found that when the spores are on the surface of the host leaves with water, the zoospores or dormant spores can be germinated and the germ tubes can be produced and infested; when the host leaves lose water, the spore infection cannot continue.

2 Tomato late blight disease seedling stage, adult stage symptom recognition

Tomato late blight occurs in leaves, stems, fruits and leaves. The diseased leaves of the disease appear water-soaked green lesions, which spread rapidly to the veins and stems, making the stems dark and dark brown rot-like. Finally, the whole plant is wilting. When the humidity is high, a white mildew layer will be produced. In the adult stage, more dark green irregular water-immersed lesions appeared in the tip and leaf margin of the diseased leaves, and then turned brown. White mold appeared on the back of the leaf and was rotted. The fruit is extremely susceptible to disease, and it is dark green oil at first. It gradually becomes an irregular cloud-like brown spot. When it encounters high humidity, it will grow a small amount of white mildew and the fruit will rot rapidly.

3 The occurrence of pests and diseases

The tomato late blight pathogens are overwintered on the protected tomato or with the diseased body in the soil. When the conditions are appropriate, the sporangia are transmitted with the air. The occurrence and epidemic of late blight are closely related to climatic conditions, and the development speed is closely related to the cultivation conditions of tomato and the disease resistance of the plant itself.

3.1 Climate conditions

Temperature has a great effect on the hostage of pathogens, mainly affecting the rate of spore germination. Fungal spores have a high germination rate at a suitable temperature, a short time required, and a long sprouting tube. The temperature is the shortest at 25 °C, only 3 to 4 days, too high temperature is not conducive to the prevalence of disease. The relative humidity of the pathogens is stricter. The severity of the disease cannot be seen only by the amount of rainfall. It should also consider how much rainy days are scattered or not. Late blight is prevalent when the average relative humidity lasts for more than 70%. It can be seen that relative humidity is the decisive factor in whether or not tomato late blight is prevalent.

3.2 Cultivation conditions

The planting density is high, the plants are luxuriant, the terrain is low, the drainage is poor, and the field humidity is too large, which is conducive to the occurrence of diseases; the thin soil plants are weak, the application of excessive nitrogen fertilizer causes the plants to grow, and the tomato grows in the middle and late stages, which is beneficial to the disease. .

3.3 Relationship between potato late blight and tomato late blight

Potato late blight provides a source of bacteria for tomato disease. It has been a good early growth of tomato, but due to the late blight in the potato fields 20 meters away, tomato is also infected with late blight. Generally, tomatoes are about 200 meters away from the incidence of potatoes, and the incidence is early; when the disease is more than 1 km, the onset is delayed. If the climate is suitable, it can spread to the whole field in 7-10 days, reaching the peak period, and all the plants will wither in about 30 days.

4 Comprehensive prevention methods

4.1 Agricultural control

4.1.1 Selection of resistant varieties

This is a key step in the production process. At present, the varieties with good effects against late blight in our district include Yuanhong, Zhongshu No. 4, Zhongshu No. 5, Yuhong No. 2, Jingdan No.1 and so on.

4.1.2 Implementing rotation

Because the diseased body left in the cultivated land is the initial source of infestation in wintering, it is not necessary to remove the diseased leaves and diseased fruits on the ground when pulling, and to avoid sudden and large occurrences due to accumulation of pathogens. Vegetables are rotated for 2-3 years.

4.1.3 Strengthening field management

Choose plots with high terrain, convenient drainage and irrigation, and rational close planting. Cultivate disease-free and strong seedlings, rationally apply nitrogen fertilizer, and increase potassium fertilizer. Drain in time after the rain. Strengthen the ventilation and light transmission, and release the wind in time to protect the cultivation of the ground, avoiding the condensation on the foliage of the plant or the appearance of water film to reduce the incidence. Thoroughly remove the leaves of the diseased plants after harvest and minimize the source of infection.

4.2 Chemical control

4.2.1 Seed treatment

Seed treatment and prevention of diseases must be carried out from various details, and disinfection of seeds is a key point. First, the seeds were sprayed with 70% mancozeb wettable powder 500 times, then soaked in water at 55 ° C for 30 minutes, and then germinated after draining.

4.2.2 Spray control

When the disease control occurs in a large area, the prevention and control begins from the seedling stage. Especially in the first bud period, a preventive medicine should be taken once. The commonly used medicines are: 58% metalaxyl Mn-Zn wettable powder 500 times liquid; 60% anti-virus hydrating powder 500 times liquid; 75% chlorothalonil Wet powder 600 times solution; 50% carbendazim WP 500 times solution, spray once every 7d-10d, continuous control 3-4 times.

The above is the occurrence of tomato late blight and the comprehensive content of comprehensive prevention and control. Welcome farmers who need it to come to Huinong.com to learn more.

Compacted Vacuum Suction Unit

Compacted Vacuum Suction Unit

ETR has independently developed an integrated vacuum pump unit composed of a water-ring vacuum pump, a gas-water separator, a vacuum solenoid valve, pipe fittings and an electrical control system. It is a simple, safe and reliable device that continuously serves the wards all day long, without occupying the ward space. The negative pressure is sourced from the vacuum pump unit.

Compacted Vacuum Suction Unit,Medical Suction Unit,Hospital Suction Unit,Hospital Suction Machine

Hunan Eter Medical Co., Ltd. , https://www.eter-tech.com