Damage to high-temperature vegetable leaves should not be ignored

Now that it has entered the hot season, all kinds of vegetables have also entered a period of vigorous growth. At this time, the proliferation of cells in various organs such as plant stems and leaves grows faster. It is precisely because of this that if there is slight negligence in the production management or improper agricultural operations, it will cause damage to the plant stems and leaves, especially the leaves of vegetables. There are leaf scorch, leaf curling, leaf dehydration, whole leaf wilting, yellow leaves, brittle and other unfavorable phenomena, which seriously affect the normal growth of plants, reducing the yield and quality of vegetables. The author's special observations of the diseases caused by the high temperatures caused by the leaves during the field visit were summarized as follows:

Bad symptoms

First, leaf blade edge scorch

In summer, some irregular necrotic spots appear on the leaves of vegetables, which may seem like some kind of invasive disease or phytotoxicity. This is not the case. The reason for this is that due to the imbalance in temperature management, the temperature of the growing environment where the leaves of the vegetables are growing suddenly or drastically decreases, and it is easy to produce the above-mentioned undesirable necrotic spots on the leaves. This may happen if the ventilation of greenhouses is poor or when the temperature of the greenhouse is extremely high. This may be the case if outdoor vegetables are exposed to bad weather such as dry hot air in late May or early June. For example, the damage to yam leaves in the Wutai area of ​​Hougang, Shouguang City, Guangdong province is one of the causes.

In addition, the spraying of foliar fertilizers or pesticides at high temperatures of 38°C may also lead to high temperature burns. Sometimes dripping at high temperatures can also cause local burns on the leaves.

Second, leaf curling, dehydration leaves, whole leaf wilting and other undesirable phenomena

In the hot season, when the temperature is above 40°C, the leaf margins of some vegetable varieties are curled downwards, especially for melons and vegetables, and they are often accompanied by dehydration at leaf edges or wilting of entire leaves. Tomatoes, on the other hand, show the unpleasant symptoms of rolling up the leaves under long-term high temperature conditions.

Third, leaves yellow, crisp

According to investigations, if the greenhouse film of the greenhouse is suddenly removed during the late spring, early summer or other high temperatures, the growing vegetable leaves may be yellow due to the sudden high temperature and strong light, and sometimes the leaves become brittle and fragile. .

Fourth, stems and leaves overgrow, internode too long

This kind of situation belongs to a kind of abnormal physiological performance that is long, there is no sudden harm in the first three situations, so often overlooked by vegetable farmers. As a result, the deterioration of the female flower of the vegetable plant can be normal but it cannot be normal. According to the analysis, the main reason is that the night temperature in the field is too high, the temperature difference between day and night is small, coupled with the soil moisture is very sufficient, the use of nitrogen fertilizer is too large, resulting in plant nutrient growth is strong, reproductive growth is inhibited. Although this situation has been well known to farmers, it is not uncommon for this phenomenon to be loosened in agricultural production.

Responses:

First of all, appropriate shading temperature control vegetables can choose to greenhouse temperature control agent or shade net, etc., but pay attention to shading time should not be too long, usually around 10:30 in the morning to around 3:30 in the afternoon. In the early summer season, the ventilation time must be flexible. The size of the ventilation should be determined according to the weather conditions. The ventilation at the bottom must be set.

Watering and fertilizing should be reasonable and neither too dry nor watery enough; fertilization should be combined with vegetables at different periods and different growth trends to determine the types and quantities of supplementary fertilizers.

Medication should be timely and appropriate in the growth stage of vegetables without pests and diseases, can be regularly sprayed with protective agents, the concentration should be in accordance with the minimum amount of instructions. In the stage where pests and diseases occur, selective drugs can be used to control diseases and insect pests in a targeted manner. Pay attention to the use of drugs to avoid the high temperature and light time, to achieve safe, rational, scientific medication, has achieved the desired control effect.

To increase the comprehensive resistance of the plants before and after the end of May each year, both the greenhouse vegetables and the open-air vegetables should be combined with spraying a certain amount of plant growth conditioners or foliar fertilizers, such as Fengshou No.1, Yunda 120, and No. , Tianda 2116, etc. can effectively improve the ability of vegetable leaves to withstand adverse environments and reduce unnecessary damage.