Reasons for Low Fruit Set in Muskmelon and Methods to Improve It

I. Reasons Why Plants Are Prone to Poor Fruit Set

1. Excessive vegetative growth or weak, spindly plants. During the growing period of muskmelon, applying too much nitrogen fertilizer or cultivating in a protected environment with high temperature and high humidity and poor ventilation prevents vegetative growth and reproductive growth from being coordinated, often resulting in excessive vegetative growth or weak, spindly plants. When plants grow excessively, stem and leaf growth consumes a large amount of nutrients, and the nutrients supplied to flowers and fruits are relatively reduced; because of insufficient nutrients, flowers and fruits drop off. If vegetative growth is too weak, the plants are short and stunted, and the accumulation of photosynthetic products is low, which can also lead to flower drop and fruit abortion.

2. Poor light conditions. Muskmelon has a relatively high light saturation point and light compensation point and is a crop that requires strong light. When planting density is too high, light deficiency easily occurs, affecting the plant's photosynthesis, which can cause poor plant growth and development and weakened vigor, and further lead to fruit abortion, which often occurs in winter and spring cultivation.

3. Poor pollination and fertilization. Although the female flowers of muskmelon are complete flowers, if artificial pollination is not carried out, the fruit set rate is relatively low. If adverse weather such as rain and low temperature occurs during flowering and fruit setting, pollination and fertilization are even less favorable, and fruit abortion is likely to occur. At the same time, artificial pollination must be timed well, and when using hormone treatment, attention must be paid to the agent concentration and even application.

4. Damage from diseases and insect pests. Damage from diseases and insect pests can also affect the normal growth and development of plants, causing poor growth and development and affecting fruit set.

II. Measures to Improve the Fruit Set Rate

1. Strengthen temperature management. During the fruit-setting period of muskmelon, the suitable daytime temperature is 28-30°C. Below 18°C or above 32°C is unfavorable for pollination and fruit set, and deformed fruits are likely to occur. The suitable nighttime temperature is 15-18°C. In greenhouse cultivation, temperature management should be strengthened. During the flowering and fruit-setting period, the main focus should be on increasing temperature, while at the same time preventing high temperature and high humidity.

2. Management measures such as pruning and fertilization. The flowering and fruit-setting period is the stage when vegetative growth transitions to reproductive growth. At this time, field management should be strengthened to coordinate the relationship between vegetative growth and reproductive growth. When fertilizing, do not apply nitrogen fertilizer alone. Prune and remove side shoots in time to control excessive vine growth. If excessive vegetative growth occurs, promptly use the method of binding the vines with the growing tip lowered to suppress stem and leaf growth and promote the distribution of nutrients to young fruits. If the plants grow thin and weak, soil topdressing or foliar spraying can be carried out to strengthen plant vigor and promote flowering and fruit set.

3. Improve light conditions. A reasonable cultivation density must be mastered. Generally, for single-vine pruning, the cultivation density per 667 sq m is 2000-2200 plants for early-maturing varieties and 1500-1800 plants for mid- and late-maturing varieties. Under the condition of meeting temperature requirements, attention should be paid to improving light conditions, using drip-free greenhouse film, cleaning dust on the film surface in time, and uncovering and covering mulching materials such as straw mats appropriately earlier and later so that plants can receive as much light as possible.

4. Carry out artificial supplementary pollination. Artificial supplementary pollination can increase the fruit set rate. When pollinating, attention should be paid to applying evenly and not using too much force, so as not to bruise the stigma and ovary. The best pollination time is 9:00-11:00 in the morning.

5. Prevent and control diseases and insect pests. Common diseases include fusarium wilt, phytophthora blight, and powdery mildew. The main insect pests are aphids, whiteflies, and others. Comprehensive prevention and control should be the main approach, and chemical control should be used promptly when diseases and insect pests are found.

6. Hormone treatment during the flowering period. Applying fruit-setting agents or other plant growth regulators can promote fruit set. Applying them to the fruitlet on the day of flowering or 1 day before flowering can increase the fruit set rate of muskmelon, which is otherwise difficult to set fruit, to more than 90%, and can also promote the enlargement of early fruits. However, attention should be paid to suitable concentration and even application.