After waterlogging, young walnut trees need early winter cold protection

The flood disaster on July 19 caused both direct damage to the trees and some derived harm, such as excessive late-season vigorous growth of young trees and prevalent diseases, which is very unfavorable for the safe overwintering of young trees. Young walnut trees have large pith in branches and trunks and loose tissue, so their cold resistance is poor. After flooding, young trees are prone to drying out and dying during overwintering, especially young walnut trees in plain areas with good soil conditions, which are more susceptible to freeze damage. Winter cold protection for young walnut trees should start from the following aspects:

First, control excessive vigorous growth of young trees in the middle and late stages. After the flood, soil moisture is good, and in plots with deep soil, walnut new shoots grow heavily and stop growing late, which is not conducive to nutrient accumulation in the trees. For 1- to 3-year-old young trees, do not apply nitrogen fertilizer from July to September, and promptly drain accumulated water in low-lying areas to prevent excessive late-season vigorous growth of young trees. For vigorous-growing trees, carry out mid-tillage and plowing in early to mid-September to cut off part of the shallow roots on the outer periphery of the young trees and inhibit new shoot growth. For vigorous shoots that have not stopped growing and have reached more than 100 cm in growth, take measures such as bending branches to open the angle or pinching the tips to force the new shoots to stop growing. At the same time, from August to September, spray 0.3% monopotassium phosphate foliar fertilizer 2 to 3 times to promote branch and bud maturity and improve the tree's freezing resistance.

Second, do a good job in autumn control of leafhoppers. Leafhoppers, also known as green leafhoppers, cause damage by laying eggs on trunks and branches as adults in late autumn (September to October). When leafhoppers lay eggs under the bark, they severely damage the bark, causing young trees to lose too much water and die from shoot drying. In autumn, there are many leafhoppers on crops and weeds, especially in plots intercropped with vegetables such as radish and Chinese cabbage, where leafhopper damage is more severe, and the damaged plant rate can reach 100%, leaving damaged trees covered with injuries. Intercropping vegetables and tall crops should be prohibited between walnut rows. For plots with severe leafhopper occurrence, use 10% imidacloprid wettable powder at 2000 times dilution for control. At the same time, before leafhoppers lay eggs (before late September), whitewash the trunks and branch crotches of young trees to reduce leafhopper damage to trunks. Whitewash formula: quicklime : salt : water at a ratio of 6:0.5:15.

Third, brush antifreeze agent to protect the trees. After walnut leaves fall and until late November, brush antifreeze agent on the branches and trunks to protect the trees. The commonly used antifreeze agent is made by boiling polyvinyl alcohol and water at a ratio of 1:15-20. Evenly brush the boiled polyvinyl alcohol solution 1 to 2 times on trunks and branches of trees 3 years old and younger to prevent young trees from losing water and drying out.

Fourth, irrigate enough water before freezing. Before mid-November, irrigate enough water before freezing to meet the water transpiration needs of the trees during dormancy and ensure the safe overwintering of young trees.

Xingtai Municipal Forestry Bureau Li Shizhong