Symptoms and prevention methods of eggplant blight

If eggplant has eggplant cotton blight, how should it be treated better? Here is an introduction

Eggplant Introduction

Eggplant blight causes large pieces of fruit to rot and fall off. It is one of the important diseases of eggplant and is common in all regions. Eggplants can be affected at any growth stage. The loss is generally 20% to 30%, and more than 50% in severe cases. The peak period of fruiting is also the peak period of disease. It often breaks out in rainy areas and years.

Eggplant blight

symptom

The main damage is to the fruit, and the stems and leaves are also affected. On the fruit, water-soaked circular or nearly circular, yellow-brown to dark brown, slightly sunken lesions initially appear, with unclear edges. After expansion, they can spread to the entire fruit surface, and the inside turns brown and rots. When it is humid, white cotton-like mold will appear on the surface of the spots. The diseased fruits fall to the ground or remain on the branches, and become dead fruits after losing water and drying. The leaf lesions are circular, water-soaked, and have obvious ring patterns. When it is humid, the edges are not obvious, and sparse white mold (sporangia and sporangiophores) will appear on the surface of the spots. When it is dry, the edges of the lesions are obvious and no white mold will appear. The flowers are wet rot and spread to the tender stems. The lesions are brown and sunken, and the upper branches and leaves wilt and smoke downward. When it is humid, white cotton-like substances (mycelium and sporangia of the pathogen) will appear on the diseased parts such as the flower stems.

pathogen

The disease is caused by infection by Phytophthora parasitica Dast. and P. capsici Leon. of the subphylum Mastozotocin. The hyphae are white, cotton-like, without septa, with many branches and well-developed aerial hyphae. A large number of sporangia are easily produced on diseased tissues and culture media. The sporangiophores are colorless, slender, without septa, and generally unbranched; the sporangia are colorless or slightly yellow, oval, spherical to oblong, and 30-70 (20-60 microns in size; the papillary protrusions at the top of the sporangium are obvious, and the size is 6.8 (6.2 microns. A large number of yellow spherical thick-walled spores can be produced at the top or in the middle of the hyphae, with a diameter of 20-40 microns and a wall thickness of 1.3-2.6 microns, which grow alone or in clusters. Some people believe that P. melongenae Sawada, also known as Phytophthora melongenae, is also the pathogen of this disease, and its characteristic is that the cotton-like hyphae are long.

Mode of transmission

The pathogen overwinters in the soil as oospores along with diseased and damaged tissues. The following year, the oospores are splashed onto eggplant fruits by rainwater, and germinate to grow germ tubes. After the germ tubes come into contact with the surface of the eggplant, they produce attachments, and invasion threads grow from their bottoms, which penetrate the host epidermis and invade. Sporangia are then produced on the lesions, which germinate to form zoospores, which are spread by wind and rain, resulting in reinfection. In autumn, oospores are formed in the diseased tissues to overwinter.

Conditions of disease

The optimum temperature for development is 30℃, and the relative humidity of air is above 95%, and the mycelium develops well. Within the high temperature range, the humidity in the greenhouse is an unimportant factor in determining whether the disease occurs or not. In addition, continuous cropping, high groundwater level, poor drainage, dense planting, poor ventilation, or rain after the canopy is removed from the protected area, or the canopy drips, causing water accumulation and humidity on the ground, are all prone to induce this disease.

Eggplant blight is a fungal disease. It is mainly spread by soil and rain. It is easy to get sick when the temperature is high and humidity, the weather is sunny after rain, the plant density is too high, the ventilation and light transmission are poor, the terrain is low, and the soil is heavy.

Prevention and treatment methods

For greenhouse eggplants to be planted in August, the following prevention and control measures can be taken:

1. Choose disease-resistant (tolerant) varieties: Generally, round eggplant varieties are more disease-resistant than long eggplant varieties, such as black eggplant, nine-leaf eggplant, etc. In addition, thick-skinned varieties are more disease-resistant than thin-skinned varieties, and early-maturing varieties are more disease-resistant than late-maturing varieties.

2. Seed disinfection: Disinfect the seeds before sowing. For example, soak the seeds in warm water at 50℃~55℃ for 7~8 minutes before sowing, which can greatly reduce the occurrence of cotton blight.

3. Use hole tray seedling cultivation: You can use 288-hole six-tray, one hole for one seed, which provides sufficient nutrients and a well-developed root system. The roots will not be damaged or will be less damaged during transplanting, which enhances disease resistance and reduces the chance of disease.

4. Implement crop rotation: The plots should be arranged reasonably, and continuous cropping with tomatoes, peppers and other Solanaceae and Cucurbitaceae crops should be avoided. Generally, crop rotation should be implemented for more than 3 years.

5. Carefully select the land. Pay attention to choosing high and dry land with good drainage, and use deep trenches and high ridges for cultivation, which is conducive to drainage after rain. Try to avoid land with heavy soil and easy water accumulation after rain.

For open-field eggplants that are in the fruit-setting period, the following prevention and control measures can be taken:

1. Mulching: Use black mulch to cover the ground or spread between rows to block the spread of pathogen spores in the soil to eggplants. It can also use sunlight for high-temperature sterilization and prevent weed growth.

2. Scientific fertilizer and water: Apply sufficient well-rotted farmyard manure, increase the application of phosphorus and potassium fertilizers, apply topdressing at the right time, irrigate with small amounts of water without water accumulation, and immediately apply cool water after heavy rain to resist infection and enhance the plant's disease resistance.

3. Careful management: prune branches in time, remove old leaves at the bottom, improve field ventilation and light conditions, remove diseased leaves and fruits in time, and take the diseased remains out of the field to prevent reinfection.

4. Chemical control: Spray the seedbed with 500 times diluted 50% carbendazim wettable powder before planting eggplant. You can also mix 5 kg of 50% carbendazim wettable powder with 100 kg of soil and sprinkle it into the planting hole. After the seedlings have grown, spray the roots of the plants with 500 times diluted 70% dichlorodiphenylmethane wettable powder or 500 times diluted 70% mancozeb wettable powder, once every 7 to 10 days.

As soon as the central diseased plants appear, they should be immediately removed, destroyed and sprayed. Spraying should be done during the fruiting period, especially before the rain, to prevent the disease. Spray 1:1:200 times Bordeaux mixture every 7 days to prevent the disease. Apply medicine immediately after the disease occurs. The medicine can be 75% thiophanate-methyl 500-600 times liquid, 50% methyl thiophanate wettable powder 800 times liquid, 40% ethyl phosphine wettable powder 200 times liquid, etc., alternately use the medicine, generally spray once every 7-10 days, and spray 3-4 times in a row.

1. Agricultural prevention and control: Choose disease-resistant varieties according to local conditions; 2. Rotate with non-Solanum vegetables for 3-4 years. 3. Strengthen field management. Plant on high ridges in waterlogged areas. Remove diseased fruits in time to prevent the spread of pathogens. 3. Spray fungicides, 75% chlorothalonil 500-800 times solution; 65% mancozeb 500 times solution; 58% metalaxyl mancozeb (Medomil mancozeb) 600 times solution; 72% chlorpyrifos 600-800 times solution; 72% purike water solution 800 times solution; 78% kobo 600 times solution; 80% dasheng 500 times solution. Spray once every 10 days or so, for a total of 2-3 times. When spraying, focus on spraying the lower fruits.