Comprehensive control methods for eggplant diseases that occur easily in the rainy season

Eggplant, also known as “qie” and by the alternate name “luosu”, is one of the few purple vegetables and is also a very common home-style vegetable on the dining table. The eggplant root system is well developed, reaching more than 1 m deep, with the main root mass distributed within the 30-33 cm soil layer. Lignification occurs relatively early, regeneration ability is somewhat poor, and the ability to produce adventitious roots is also weak. In greenhouse cultivation, if the branching habit is allowed to grow naturally, it will create shade inside the greenhouse, affecting ventilation and light penetration for the eggplant, worsening diseases and reducing yield. For this reason, scientific pruning must be carried out during cultivation.

The eggplant flower is bisexual, mostly solitary, with some in clusters of 2-4, white or purple, fused at the base into a tube shape. Eggplant has a high self-pollination rate, with the natural cross-pollination rate between 3% and 6%. According to differences in style length, it can be divided into three types: long-styled flowers, medium-styled flowers and short-styled flowers. In long-styled flowers, the stigma extends above the anthers; the flower is large and deep in color, and pollination readily occurs on the stigma, making it a sound flower. In medium-styled flowers, the stigma is level with the anthers, and the pollination rate is lower than that of long-styled flowers. In short-styled flowers, the stigma is lower than the anthers; the flower is small and the pedicel is thin, and the chance of pollination on the stigma is very low, so usually almost all flowers drop, making it an unsound flower. The eggplant fruit is a berry, round, long club-shaped or ovoid in shape, and purple, red-purple, green, white, etc. in color. The seeds are flat and round, with a smooth and hard outer coat, and the 1000-seed weight is about 5 g.

Comprehensive control of eggplant diseases that occur easily in the rainy season

In recent years, eggplant Verticillium wilt and Phytophthora blight have become the two diseases with the highest incidence in eggplant production, often occurring severely in rainy years and seasons, reducing yield by 20%-30% in mild cases and by more than 60% in severe cases, causing great economic losses to vegetable growers. Eggplant Verticillium wilt is also called half-side madness and black heart disease, while Phytophthora blight is also called dropping eggs and rotten eggplant; the former damages leaves, while the latter mainly damages fruit.

1. Common conditions for disease occurrence

The conditions for the occurrence of Verticillium wilt and Phytophthora blight are basically the same. Continuous rain, high temperature and high humidity are all favorable for large-scale epidemics of the two diseases. The suitable temperature for disease occurrence is 20°C-30°C; within this range, the higher the humidity, the higher the incidence. In addition, low-lying wet vegetable fields, heavy clay soil, extensive management, multiple continuous cropping cycles, overgrown weeds, overly dense planting, application of incompletely decomposed organic fertilizer and damage by underground pests are all favorable for disease occurrence.

2. Symptom identification

Verticillium wilt symptoms: It mainly damages leaves and can occur at all growth stages of eggplant, with the fruiting stage being the most severe. At the early stage of disease, pale yellow spots appear between the veins of the lower leaves, gradually spreading to half a leaf or the entire leaf. Diseased leaves wilt during the day and recover at night; the color changes from yellow to brown, the edges curl upward, and finally the entire leaf dies and drops off. When the disease is severe, it can spread to the whole plant.

Phytophthora blight symptoms: It mainly damages fruit and can also damage leaves, stems and flowers. Fruit becomes infected when nearing maturity, so in the field the middle and lower fruits are affected more. At first, a nearly circular dark brown, water-soaked lesion appears on the fruit. When conditions are suitable, it rapidly expands and gradually causes the entire fruit to rot. When field humidity is high, the lesion becomes covered with white mold-like mycelium. Infected leaves show obvious concentric rings, and when stems are severely infected, the stems dry up and die.

3. Comprehensive control

1. Seed disinfection. Choose disease-resistant varieties, such as Changqie No. 1; disinfect the seeds before sowing, for example by soaking them in warm water at 50°C-55°C for 7-8 minutes, or soaking them in a 1000-fold formalin solution for 15 minutes, then washing them clean and sowing directly.

2. Crop rotation. Avoid continuous cropping or adjacent cropping with Solanaceous vegetables such as tomato and pepper.

3. Use plug tray seedling raising. One plant per plug cell, evenly distributed, with sufficient nutrients and a well-developed root system, causing no or little root damage at transplanting. This enhances disease resistance and reduces opportunities for infection.

4. Apply fully decomposed organic fertilizer.

5. Strengthen post-transplant disease control management. First, thoroughly clean the field after harvest; all plants, together with diseased plants, should be taken out of the field and destroyed, and must not be discarded at random. Second, timely cultivate and earth up to promote plant root growth. Third, plant at a moderate density, pull out weeds in the field, remove some old leaves at the bottom, and improve ventilation and light penetration in the field.

6. Chemical control. At transplanting, use 5 kg of 50% carbendazim wettable powder per mu mixed with 100 kg of fine soil and scatter it into the transplanting holes; after transplanting, spray the plant roots with 500-fold 70% dexon wettable powder solution or 700-fold 50% benomyl solution, spraying once every 7-10 days. Since these two diseases are relatively severe epidemic diseases during the eggplant growing period, and the flowering and fruiting stage of the plant coincides with the high-temperature and rainy season, preventive spraying should be carried out once every 7-10 days: 500-fold 58% ridomil mancozeb solution or 500-fold 64% sandofan solution or 300-fold 40% phosethyl-Al solution used in rotation can achieve relatively good results.