Schisandra chinensis sunburn disease

Fruit sunburn of Schisandra chinensis is a common physiological disease, which causes certain losses in production every year. With the global warming, this disease has a trend of increasing year by year.

1. Disease symptoms Schisandra sunburn mainly harms the fruit. Sunburn sites often show herpes, sunken spots, leatherization, plaque sclerosis or pulp tissue withered spots. The surface of the damaged fruit turned white (yellow or pink) at first, and then turned black-yellow to brown. When the burning occurred seriously, sunken necrotic spots appeared in the pulp tissue and necrotic tissue appeared in the local pulp, and the injured parts were easily infected by other fruit rot bacteria and caused fruit rot.

two。 The direct causes of sunburn are thermal injury and ultraviolet radiation injury, in which thermal injury refers to sunburn caused by high temperature on the fruit surface, which has nothing to do with light, while ultraviolet radiation injury is sunburn caused by ultraviolet radiation, which will lead to cell collapse. The occurrence of sunburn is related to many factors, such as temperature, light, relative humidity, wind speed, variety, fruit development period, tree potential and so on. Temperature and light are the main influencing factors. ① temperature and air temperature are important factors affecting the sunburn of Schisandra chinensis fruit. In the sunny and hot summer day, the surface temperature of Schisandra chinensis fruit can reach 40-50 ℃, which is much higher than the highest temperature of the day. Some scholars believe that the critical temperature causing sunburn is between 30-32 ℃, and with the increase of ambient temperature, the time of sunburn shortens, and the harm degree of sunburn increases. ② light, light intensity and ultraviolet light are important factors for sunburn of Schisandra chinensis fruit. Under natural conditions, the fruit receiving light converts part of the light energy into heat energy, thus increasing the surface temperature of the fruit, coupled with the warming effect of high temperature on the fruit, resulting in the fruit surface reaching the critical sunburn temperature, thus inducing the occurrence of fruit sunburn.

The disease occurred from June to September, and the peak of the disease was in the summer of high temperature and strong light from July to August. In production, it is often found that the peak of fruit sunburn every year always coincides with the highest temperature in the year. Under the premise of high temperature, sunburn can easily occur in sunny days, while the incidence of sunburn in sunny days with low temperature is low. The lower the relative humidity, the higher the incidence of sunburn; the wind speed can change the fruit temperature by regulating transpiration, and the breeze can reduce the fruit surface temperature to reduce the incidence; different varieties have different sensitivity to sunburn; the fruit has different resistance to sunburn at different development stages, and the sensitivity to sunburn decreases with the ripening of the fruit. In the same orchard, the incidence of sunburn was low in those with strong trees, and serious in those with weak trees.

3. Control technology ① strengthen cultivation management, enhance tree potential, pay attention to prevent excessive application of nitrogen fertilizer, apply more organic fertilizer, improve soil water and fertilizer conservation capacity, promote plant root system development in depth, and improve plant early resistance. ② pruning should leave more branches and leaves to avoid fruit exposure to direct sunlight; through flower and fruit thinning, adjust to determine a reasonable branch-fruit ratio, leaf-fruit ratio. ③ can reduce the surface temperature of fruit by cold sprinkler irrigation before the coming of high temperature, which can effectively avoid sunburn. ④ adopts fruit bagging, which can reduce sunshine intensity and fruit surface temperature.