How should pepper seedlings be managed in a warm winter climate?

In recent years, with global climate warming, winter temperatures have been getting higher and higher. In Yongzhou City, during the past winter and this spring, there were several periods with temperatures higher than the same period in previous years. Such continuously high temperatures caused excessive vegetative growth of pepper seedlings, bringing great difficulties to cultivating strong seedlings. In particular, continuous high temperatures followed by a sudden drop in temperature and then a sudden clearing of the sky can cause water loss, scorching and wilting of new pepper leaves, and trigger a major outbreak of gray mold. Under such conditions, the incidence of gray mold in the pepper seedlings of our college's Landscape Architecture Department reached 10%, and in some severely affected plots it exceeded 50%, seriously affecting the rate of strong pepper seedlings. For this situation, we can take the following measures to prevent it:

1. Early low-temperature hardening of seedlings

In general, the conventional seedling-raising method does not lower the temperature to harden seedlings at an early stage, but waits until 10-15 days before transplanting to begin lowering the temperature for hardening, until the greenhouse no longer needs to be closed at night at transplanting time. However, to prevent the effects of a warm winter, hardening should be considered once the seedlings emerge, so as to enhance the cold resistance of the seedlings and prevent sudden weather changes. But at this time, low-temperature hardening must not be excessive; otherwise, it easily results in stiff seedlings. Generally, the method of closing the greenhouse late (closing only after dark) and opening it early (opening as soon as morning comes) is used to give the seedlings low-temperature training. After low-temperature training, the seedlings can become darker in color, thicker in leaves, and significantly stronger in their ability to resist sudden weather changes.

2. Water less and properly control seedling growth

In general warm winter weather, there are more sunny days, the seedbed soil dries easily, and the chances of watering are naturally more frequent, but this very easily leads to excessive vegetative growth and overly tender seedlings. To prevent excessive vegetative growth of seedlings, the requirement is not to water unless the seedbed soil is dry; even if the seedbed soil is dry, watering should also be delayed, extending the interval between waterings. Even during continuous sunny days, it is enough to water thoroughly just once. If the leaves show mild wilting, you can wait until evening and use a sprayer to mist water. As long as it is not severe wilting, never spray water at noon under high temperature, because this will make the seedlings even more tender and lower their stress resistance. Through several years of observation and practice, I have found that this method is extremely beneficial for cultivating strong seedlings.

3. Properly spray paclobutrazol

When seedlings are found to have a slight tendency toward excessive vegetative growth, promptly spraying paclobutrazol can effectively prevent excessive growth and scorching caused by water loss in new leaves. According to observation, among seedlings sprayed with paclobutrazol, only 1%-2% showed scorching caused by water loss in new leaves. Moreover, the time for recovery growth after water loss was generally 1 day, and at the latest no more than 2 days. After recovery, the seedlings grew robustly and rarely became infected with gray mold. In contrast, among seedlings not sprayed with paclobutrazol, the rate of scorching caused by water loss reached 40%-50%, or even higher, and after being damaged, the number of days needed to resume growth was 3-5 days. After resuming growth, their growth vigor was weak, and they were highly susceptible to gray mold. It is worth noting that the concentration of paclobutrazol sprayed must not be too high; 2000 times is better, otherwise it will inhibit the growing point and cause a large number of lateral branches to develop, affecting yield and early maturity.

The above 3 measures have played a very good preventive role against excessive vegetative growth of pepper seedlings, scorching of new leaves, and water loss. Once this situation occurs, necessary measures should be taken promptly to reduce losses to a minimum. For example, on the morning of the day symptoms appear, open the greenhouse early to prevent excessive temperature differences inside the greenhouse from worsening water loss; second, use a sprayer to mist water, and it can be sprayed several times to prevent leaf dehydration; near noon, you may also consider covering the greenhouse with a shade net to block light and lower the temperature, then uncover the shade net in the afternoon. In severe cases, it can remain covered for several consecutive days until the seedlings resume growth.