What are the control methods for eggplant Phytophthora rot?
Eggplant Phytophthora rot, also known as rotten eggplant, dropped fruit, watery rot, etc., occurs commonly in all vegetable-growing areas and can harm both open-field and protected-cultivation eggplant. In years with heavy rain in early summer or during the plum rain season, or with heavy rain and fog in autumn, the disease is severe, and when it breaks out severely it often causes large numbers of fruits to rot, directly affecting yield. Let's take a look together at the control methods for eggplant Phytophthora rot!
Symptoms
When eggplant seedlings are affected, the base of the stem becomes water-soaked and develops very quickly, often causing damping-off and leading to seedling death. When leaves of mature plants are infected, irregular water-soaked lesions appear, with obvious concentric rings but indistinct edges, brown or purplish-brown, and a small amount of white mold grows on the lesions when humid. Affected stems become water-soaked and constricted, sometimes breaking, and grow white mold. After flower organs are infected, they turn brown and rot. Fruits suffer the most severe damage: water-soaked round spots first appear, with indistinct edges, slightly sunken, yellow-brown to dark brown. The flesh of the diseased part becomes dark brown and rotten, and under high humidity the surface of the diseased part grows white cottony mycelium; diseased fruits drop easily or shrivel and contract into mummified fruits.
Conditions for disease development
The optimum temperature for development is 30°C, and mycelial growth is good when relative air humidity is above 95%. Within the high-temperature range, humidity inside the greenhouse is an important factor determining whether the disease occurs. In addition, continuous cropping land, high groundwater level, poor drainage, dense planting, poor ventilation, or rain after the curtain is removed in protected cultivation, or dripping from the curtain, causing waterlogging and dampness on the ground, all easily induce this disease. It is prone to occur under high temperature and high humidity, sudden clearing after rain, excessively high plant density, poor ventilation and light penetration, low-lying terrain, and heavy clay soil.
Open-field control
1. Plastic film mulching: Using black plastic film to cover the ground or laying it between rows can block the splash transmission of pathogen spores from the soil to eggplant fruits. It can also use sunlight for high-temperature sterilization and prevent weed growth.
2. Scientific fertilization and watering: Apply sufficient decomposed organic fertilizer, prevent high temperature and high humidity, and increase the application of phosphorus and potassium fertilizers to promote robust plant growth and improve plant resistance.
3. Careful management: Prune at the right time, remove lower old leaves, improve field ventilation and light conditions, promptly remove diseased leaves and fruits, and take diseased residues out of the field to prevent re-infection.
Greenhouse control
1. Resistant varieties: such as Xingcheng Purple Round Eggplant, Guizhou Winter Eggplant, Tongxuan No. 1, Jinan Early Small Long Eggplant, Bamboo Silk Eggplant, Liaoqie No. 3, Fengyan No. 11, Qingxuan No. 4, Laolaihei, etc.
2. Seed disinfection: Disinfect seeds before sowing, for example soaking seeds in warm water at 50°C-55°C for 7-8 minutes before sowing, which can greatly reduce the occurrence of Phytophthora rot.
3. Plug tray seedling raising: 288-cell trays can be used, with one seed per cell; nutrients are sufficient, the root system is well developed, and roots are not damaged or are less damaged at transplanting, which enhances disease resistance and reduces the chance of infection.
4. Practice crop rotation: Arrange plots reasonably, and avoid continuous cropping with Solanaceae and Cucurbitaceae crops such as tomato and pepper. Generally, a rotation and crop change of more than 3 years is practiced.
5. Careful site selection: Choose high, dry plots for planting eggplant and plow the soil deeply. Use high-ridge cultivation and cover with plastic film to block the spread of pathogens from the soil to the aboveground parts and promote root development.