What are the causes of and control methods for rapeseed seedling death?

Rapeseed is a major oilseed crop, widely cultivated in both northern and southern regions, and various diseases occur during the growing process. But sometimes rapeseed plants show the same symptom yet it is not caused by the same damaging factor; for example, rapeseed seedling death may be caused by disease, or it may also be caused by disease. It may also be a physiological injury caused by weather. Why not take a look together at what exactly causes rapeseed seedling death and how to deal with it.

I. Causes

1. Insect pests

Aphids gather to suck leaf sap, causing leaves to wither and yellow; in severe cases seedlings die, or serious damage by cabbage white butterfly or flea beetles can cause seedling death. Under high temperature, frequent rain and high humidity, diseases such as viral disease and downy mildew occur and spread in large numbers.

2. Water

Severe drought at sowing time, or continuous overcast and rainy days, can cause seeds to die and fail to emerge, which amounts to seedling death. After seedlings emerge, heavy rain or waterlogging in low-lying areas causes root rot, and they cannot respire and die. If drought occurs and irrigation is not timely, it causes an irreversible state of water loss and the seedlings wither and die; or if you water at noon on a sunny day during drought, seedling scalding occurs.

3. Density

If planting density is too high, the seedlings have insufficient growing space and receive insufficient light, and underground they must compete for water and nutrients, so some seedlings become weak and gradually die. Or if sowing is too early, the seeds do not adapt to the temperature after emergence and suddenly die.

II. Preventive measures

1. Prevent pests and diseases

When aphids are found, spray to control them, preventing them from sucking leaves and transmitting viral disease. Once a few seedlings with downy mildew are found in the field, be sure to spray chemicals promptly to control the outbreak and prevent the pathogen from multiplying massively and worsening the disease.

2. Control water

Before sowing, check what the weather will be like in the coming period. If drought occurs at the seedling stage, be sure to irrigate by flooding every evening shortly after the drought occurs to restore growth. If there is heavy rain or continuous overcast and rainy weather, check the ditches and drain promptly to prevent waterlogging, and spread a certain amount of plant ash to absorb moisture and prevent disease from high humidity.

3. Seedling management

Rapeseed is generally planted in November, so raising seedlings in October in advance is fine; do not transplant too early, and transplant only when the growing temperature is reached. When sowing and raising seedlings, be sure to use seedling trays with clearly divided specifications to ensure each seedling has enough growing space and they are not competing with each other for nutrients. Or, when raising seedlings in a seedbed, thin and transplant the seedlings promptly after they emerge uniformly.

From sowing to emergence, and then to seedling management after transplanting, these are all fragile periods for rapeseed growth and require careful management; otherwise direct seedling death in rapeseed will consume a great deal of time for replanting and waste manpower and resources. Overall, prevention should be the main approach, supplemented by improving treatment.