1, embryonic dysplasia. Embryo dysplasia or degeneration. The frequency and proportion of seedless watermelon seedlings are far greater than seedless watermelon seedlings.
2. Seeds are out of date. Years of old seeds and poor storage conditions have reduced or even lost the viability of some seeds.
3, low temperature frostbite. When raising seedlings, the temperature of seedbed is too low, or the temperature of the growing point of some seedlings (between two leaves) is too low to condense water droplets, resulting in freezing damage to the growing point.
4. Some pests. Watermelon seedlings can be capped by themselves when they are harmed by pests such as tobacco thrips (also known as onion thrips and cotton thrips). For example, adults and nymphs of tobacco thrips can file and suck the juice of watermelon heart leaves and flower buds in early spring to stop the growth of growing points.
5, fertilizer damage, drug damage. The newly unearthed melon seedlings have tender growth points, weak resistance to fertilizers and drugs, high concentration of foliar spraying or topdressing, and large amount of spraying, which is easy to destroy the growth points.
6. Low temperature obstacle and high temperature obstacle. When seedlings encounter bad weather, the seedbed temperature is too low, which makes them vulnerable to freezing injury, and the growing points are often frozen to death and missing. When the seedlings meet sunny days, the sun shines directly on the seedbed in the afternoon, which makes the temperature in the seedbed too high, especially when the humidity of the seedbed is low, the growing points are easy to burn, and even the young leaves are easy to lose water, dry and crack, and even die in serious cases.
7. During the emergence of watermelon, when the ground temperature is too high and the air temperature is too low, or when it meets the cold ice and low temperature for a certain period of time, the differentiation of growth points is inhibited and it can't grow normally, that is, the seedlings can't see obvious growth points when the cotyledons are open.
8. The seedlings develop normally at the initial stage of growth, and the growing points are exposed. Later, due to low temperature, excessive water control or severe water shortage in dry weather, the growing point was small or did not grow.
9. In the process of seedling growth, the growing point is suddenly injured by cold air, toxic and harmful gases or improper application of drugs, resulting in the growth point stopping or even dying.
10 is a physiological disease that hinders the growth point of melon seedlings. In addition to manual measures, chemicals should also be combined with prevention and control. Spraying liquid medicine in time at the initial stage of symptoms can regulate the physiological metabolism of the whole melon seedling, promote the cell division and root development of the melon seedling, improve the physiological activity of the melon seedling and promote the normal development of the growing point.