What causes flower and fruit drop in eggplants?
What causes flower and fruit drop in eggplants? How can it be prevented and controlled? In eggplant production, flower and fruit drop is usually severe, restricting yield improvement and reducing production efficiency, so prevention and control should be emphasized in production. The main causes of flower and fruit drop in eggplants are: 1. Unsuitable temperature. The fruiting period of eggplants requires relatively high temperatures...
What causes flower and fruit drop in eggplants? How can it be prevented and controlled?
In eggplant production, flower and fruit drop is usually severe, restricting yield improvement and reducing production efficiency, so prevention and control should be emphasized in production.
The main causes of flower and fruit drop in eggplants are:
1. Unsuitable temperature. The fruiting period of eggplants requires relatively high temperatures; the optimum temperature during the fruiting period is between 25-30°C, and the nighttime temperature should be between 15-20°C. When the temperature is below 15°C or above 35°C, growth is slow and flower drop is severe, which in production appears as fewer fruits set in the early period and in summer.
2. Poor flower development. When eggplant flowers develop well, the flowers are large and deeply colored, and at flowering the style is longer than or equal to the anthers, which favors pollination and fertilization and results in good fruit set. When development is poor, the style is shorter than the anthers, pollination is difficult to achieve, and most flowers drop.
3. Nutrient deficiency. When fertilizer and water are lacking, the plant grows thin and weak, nutrients are used to maintain growth, reproductive capacity is low, and fruit set is poor.
4. Topdressing not timely or at improper times is also unfavorable for fruit set. It generally appears as topdressing too early, causing excessive vegetative growth and leading to flower and fruit drop. When topdressing is not timely, the plant declines prematurely and production capacity decreases, which is also unfavorable for fruit set.
5. Improper fertilization ratios cause the plants to grow excessively or become weak, so the balance between vegetative growth and reproductive growth is disrupted, and fruit set is also difficult.
6. Poor light. When photosynthetic capacity is low, flower quality is poor and flowers easily drop; eggplant is a light-loving crop with relatively strict light duration requirements. When light is weak, plant growth and development slow down, fewer flowers form, and flower bud quality is poor.
7. Damage from diseases and pests reduces the plant's photosynthetic capacity, which is unfavorable for the accumulation of photosynthetic products and also unfavorable for flower formation and fruit set. The main diseases and pests damaging eggplants include Verticillium wilt, aphids, red spiders, and others.
Verticillium wilt generally does not occur at the seedling stage. It mostly occurs during the fruit-setting period, developing from the bottom upward or from one side to the whole plant. The leaves turn yellow at the leaf margins and between the veins, then develop to half a leaf or the whole leaf turning yellow. Photosynthetic capacity decreases, nutrient accumulation is reduced, and the fruit-setting rate declines.
Aphids mostly gather in groups to cause damage, using needle-like sucking mouthparts to suck the host's sap, causing leaves to turn yellow, shrink, become deformed, and wither.
Red spider adults or nymphs can both feed on plant sap, causing leaves to discolor or dry up, reducing the leaves' photosynthetic capacity and making fruit set unfavorable.
Based on the above causes, corresponding measures should be taken in eggplant production to promote an increase in the fruit-setting rate and improve production and management efficiency. The main measures are:
1. Pay attention to promoting the growth of long-styled flowers and reducing the proportion of short-styled flowers, so as to help increase the fruit-setting rate. The key measure to apply in production is to strengthen temperature management during the flowering and fruiting period. Within the suitable temperature range for the fruiting period, keep the temperature slightly lower, controlling it at around 25°C during the day and between 15-20°C at night, so that flower bud differentiation is slightly delayed, which favors the formation of long-styled flowers and can effectively control the proportion of short-styled flowers. In addition, planting schedules should be reasonably arranged in production so that during the fruiting period the daytime temperature is above 25°C and the nighttime temperature is between 15-20°C. During high-temperature summer periods, attention should be paid to watering to lower the temperature. If there is continuous high-temperature weather, a shade net can be used to build a shade shelter to lower the temperature and promote an increase in the fruit-setting rate.
2. Strengthen fertilizer and water management, keep plant growth moderate, and balance the relationship between vegetative growth and reproductive growth to help increase the fruit-setting rate. In particular, the first topdressing should be applied at the right time, preferably when the first layer of fruit is 3 cm in diameter. Apply topdressing at the appropriate time to prevent fertilization from being too early, which can lead to flower and fruit drop. After that, apply topdressing once after each fruit harvest to supplement nutrients and prevent premature plant decline, which can reduce production capacity. In addition, attention should be paid to using appropriate fertilization ratios to prevent unbalanced fertilization from causing an imbalance between vegetative growth and reproductive growth. In particular, attention should be paid to preventing excessive nitrogen application, which can cause excessive vegetative growth. In general, the suitable ratio of nitrogen, phosphorus, and potassium in eggplant production is 2:1:1.7. In production, observe plant growth and use methods of promoting weak plants and controlling vigorous ones to balance plant growth.
3. Strengthen plant shape adjustment and ensure good air and light penetration for the plant to help fruit set. In production, attention should be paid to timely removal of old branches and old leaves. Because eggplants generally form flowers and set fruit at branching points, production should focus on promoting branching. Generally, the fruits set at the first, second, and third branching points are mostly effective flowers that can develop and set fruit well, while after the fourth branching point, flower bud differentiation is poor and the fruit-setting rate is low, with most being ineffective flowers. Therefore, in production, attention should be paid to removing branches after the fourth branching point to control the number of branches in the field, concentrate nutrient supply, and help fruit set.
4. Strengthen disease and pest control. In production, strengthen the control of Verticillium wilt, red spiders, and aphids. Before sowing, soak seeds for 1 hour with 50% carbendazim wettable powder at 0.2% of seed weight, or soak seeds in 55°C warm water for 15 minutes, then cool in cold water and pregerminate. In the planting field, broadcast carbendazim per mu for soil disinfection. At the initial stage of Verticillium wilt occurrence, use 50% mixed sulfur suspension concentrate or 50% carbendazim wettable powder at 500 times dilution for root irrigation, applying 500 ml per plant.
After red spiders occur, spray 1.8% Nongkemite emulsifiable concentrate at 2000 times dilution or 2.5% Tianwangxing at 3000 times dilution for control. At the initial stage of aphid occurrence, spray 50% pirimicarb wettable powder at 2000-3000 times dilution, or 21% mieshabi at 3000-4000 times dilution, or 10% imidacloprid at 3000 times dilution for control.
For plants damaged by diseases and pests, promptly spray foliar fertilizers such as Yemianbao, Zhibaosu, 0.5% urea + 0.5% potassium dihydrogen phosphate on the leaves to supplement nutrients, improve the leaves' photosynthetic capacity, increase the accumulation of photosynthetic products, and thereby increase the fruit-setting rate.
5. Spray chemical substances to protect flowers and fruits. 1-2 days before flowering, apply 30-40 ml/kg of 2,4-D to the calyx or fruit stalk; after the first layer of fruit has set, spray 120 ml/kg or 180 ml/kg or 200 ml/kg of sodium bisulfite, which can effectively increase material accumulation and improve the fruit-setting rate.
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