What should I do if watermelon seedlings become wilted in early spring?

When watermelon seedlings are raised in early spring, they may wilt when encountering rainy weather. There are several possible reasons:

1. Retting and cold roots

? Symptoms: The seedlings grow slowly, the leaves shrink and wilt, the roots initially turn yellow and rusty, and new roots are delayed and become sticky and rotten until the upper part of the seedlings wilt and die. This disease is mainly caused by excessive soil moisture and low soil temperature. Under conditions of low soil temperature and high humidity, root development is hindered, the regeneration ability, absorption function, and respiration of the roots are severely inhibited, and root hairs die in large numbers, causing the above-ground parts to wilt. Controlling temperature and humidity is the key to strengthening seedbed management. At present, the Pucheng planting area uses matrix plug trays to raise seedlings. It is required that the matrix material must have sufficient moisture when loading into trays, and the moisture content is required to reach more than 80%. The nursery shed is required to have heating equipment such as ground wires and fire walls, and the outer shed is equipped with insulation equipment such as straw curtains or quilts. In case of low temperature rain and snow, it can be adjusted manually. Strengthen the management of temperature and humidity in the nursery. The ground temperature during the seedling stage is controlled at 15-25°C. During the cotyledon stage and the two true leaves unfolding period, the daytime temperature is controlled at 22-28°C. The night temperature is controlled at 18-13°C. The moisture content of the substrate is controlled at 60% of the soil's maximum water-holding capacity. Proper control of ventilation Time and ventilation allow seedlings to thrive. Rescue measures

After slight root retting occurs, the soil is too wet. Spread fine dry soil or coal ash in time to absorb water and reduce the humidity of the seedbed. In cloudy, rainy and snowy days when the temperature is low, use geothermal heating wires or fire walls, and build small plastic arches in the shed for temporary heating and insulation. If the seedbed is short of water, you can use a sprayer to properly replenish water. Flood irrigation is strictly prohibited.

2. Symptoms of damping-off disease at the seedling stage

Damping-off disease is a disease of watermelon at the seedling stage. In the early stage of damage, the seedlings show water-soaked lesions near the base of the ground, and then the diseased parts turn yellowish brown. However, if the cotyledons have not withered and shrunk like threads, the seedlings will fall over in pieces.

Prevention

Strengthen seedbed management, do a good job of insulation and ventilation, do not water on rainy days, and keep the seedbed dry and moist. Rescue measures

When diseased seedlings are found, remove them promptly and spray them with 500-800 times of 15% Hymexazine for control.

3. Symptoms of blight in the seedling stage

Watermelon blight mostly occurs in the middle and late stages of seedling cultivation. Newly unearthed seedlings are affected, and oval dark brown lesions appear at the base of the stem. The diseased seedlings wilt during the day and return to normal at night. When the lesions circle the stem, the diseased part becomes sunken, the base of the stem dries up and shrinks, and the seedlings fall down and die. Prevention

After the watermelon emerges, strictly control the temperature, humidity and light, gradually increase the ventilation volume, and reduce the temperature and humidity of the seedbed to facilitate the cultivation of strong seedlings. Rescue measures

When diseased seedlings are found, remove them promptly and spray 58% metalaxyl manganese zinc 500 times once every 7 to 10 days.

4. Early-stage tall-legged seedlings

? Symptoms

Compared with normal seedlings, watermelon "tall-legged seedlings" have young stems that are slender and light in color. , the cotyledons are thin and small, light green in color and other characteristics. Tall seedlings are mostly caused by high temperatures, excessive humidity, and insufficient light during the seedling emergence period. Such seedlings have insufficient tissue, are malnourished, have poor resistance, and are prone to wilting and lodging when exposed to harsh environments. Prevention

From the time when the seeds emerge from the top of the soil to when the cotyledons are flattened, the hypocotyl of the melon seedlings grows faster and is more sensitive to temperature changes. The seedbed should be kept at a low temperature of 20-25 degrees during the day. , 12-15 degrees at night; and appropriately reduce the humidity of the seedbed; on the premise of ensuring that the melon seedlings are not damaged by freezing, appropriately remove the straw curtains and other coverings on the shed early and late to extend the exposure time and prevent the appearance of "high-legged seedlings".

5. Symptoms of flashing seedlings and dull seedlings

Watermelon seedlings cannot quickly adapt to drastic changes in temperature and humidity, resulting in sudden water loss, causing leaf edges to roll up, and even dry and cracked leaves. It is called "flash seedlings"; while withering caused by excessive temperature rise and insufficient ventilation is called "stuffy seedlings".

Generally, the temperature rises faster than the ground temperature, and the ratio of the two warming amplitudes is usually 4:1. If the temperature rises too fast and the gap between it and the ground temperature is too large, the melon seedlings will lose water from the stems and leaves too quickly, and the roots will not absorb enough, causing the melon seedlings to lose water and wilt.

This situation often occurs on the first sunny day after many days of rainy weather, so we must pay enough attention to it. Prevention

To prevent the seedbed from heating up too quickly, causing the melon seedlings to lose water, the following measures should be taken: In the morning on a sunny day after a long period of cloudiness, the light in the seedbed should increase from weak to strong, so that the temperature of the seedbed slowly rises, and the ground temperature When it rises to about 20 degrees, see full light again. In continuous rainy weather, warming measures should be taken to keep the ground temperature within 10 cm of no less than 15 degrees to maintain strong absorption capacity of the roots. Remedy

If you find that the melon seedlings are wilting, shade them in time to cool down, spray an appropriate amount of water, close the vents, and increase the air humidity in the seedbed to help the melon seedlings recover as soon as possible. In rainy weather, especially on continuously cloudy days, the straw curtain should be properly lifted to allow the seedlings to see the light. If the temperature is too low, use incandescent lamps to supplement the lighting in the shed. Foliar spray of Sea Spirit Biostimulant Foliar + Brassinolide Remedy. Summary

The wilting of seedlings caused by cloudy and rainy days during the greenhouse watermelon seedling cultivation period is mainly due to poor growth of seedlings caused by low temperature, high humidity, and short exposure to light; while watermelon "flash" generally occurs on cloudy and rainy days. On the first sunny day after that, as long as you pay a little attention on that day, there won't be any major problems.

Once an adverse situation occurs, you must take corresponding remedial measures decisively and do early disease prevention to strive to reduce losses!