In summer, sunburn of kiwi fruit is prone to occur under strong light, high temperature, and drought conditions. After the fruit is damaged, the pericarp is sunken, forming irregular reddish-brown necrotic spots, the surface is rough like leather, the quality of the fruit is reduced, the flavor is poor, it is not resistant to storage, seriously loses its edible value, and is easy to become soft and rot, and the sunburned fruit is easy to fall off. Therefore, preventing the occurrence of sunburn in summer is an important task. The key measures to prevent and control sunburn are to shade and protect fruit and enhance tree vigor.
One of the causes of sunburn in kiwifruit is overloaded tree fruiting, especially for varieties with low tree vigor and low resistance. Controlling the amount of fruiting is an effective measure to reduce or eliminate sunburn. When the fruit expansion is not large and the growth is obviously slow, fruit thinning should be carried out at any time to reduce the load. In addition, under natural conditions without shading, the surface temperature of kiwifruit leaves and fruits is extremely high, and the transpiration is strong. The photosynthesis of leaves has a serious "lunch break" phenomenon, and the tree is in a serious state of stress; shading can reduce the temperature to a certain extent. Humidification improves the microenvironment of kiwifruit canopy, greatly reduces leaf temperature and fruit temperature, and effectively eliminates the "lunch break" phenomenon of leaf photosynthesis. The suitable shading intensity of 'Cuiyu' is about 25%, and that of 'Miliang No. 1' is about 50%. Shading had no significant effect on the leaf transpiration rate of 'Cuiyu', but had a greater effect on 'Miliang No.1'. It can be seen that moderate shading can effectively alleviate the harm of high temperature and strong light to kiwifruit in summer, but excessive shading has negative effects. When pruning in summer, leaving a few more leaves above the fruit can also increase the thickness of the leaf curtain layer, especially for weak trees. Leave more leaves to block the direct sunlight on the fruit. The bagged fruit can open the ventilation hole and reduce the temperature in the bag. When high temperature persists in summer and there is little rain, irrigation should be strengthened, and the water content of the soil should be kept at about 75%. For orchards with conditions, it is best to spray water once every other day in the morning and evening, so as to supplement the water lost by tree body transpiration and reduce the water loss. orchard temperature. Orchard mulching can effectively reduce ground water evaporation, lower ground temperature, improve the microclimate in the orchard, enhance tree vigor, improve stress resistance, and control the incidence of heat damage. It is a good orchard management method.
