Remedial measures for frozen eucalyptus trees

The main manifestation of freezing injury of eucalyptus is frozen tip, and severe aboveground parts freeze to death. The severity of freezing injury varies according to eucalyptus variety and forest age. Eucalyptus urophylla, Eucalyptus grandis and Eucalyptus Dunn are the more cold-tolerant species of Eucalyptus, while Eucalyptus urophylla and Eucalyptus urophylla have poor cold tolerance. The main anti-freezing technical measures are as follows: 1. Slight frost injury (the top is frozen): it will not have much effect on the growth of the following year, as long as it is managed according to the routine and pay attention to keep the top strong lateral buds. 2. Moderate freezing injury (1 stroke 2 or more): regardless of age, it is best to cut off the stem at a distance of 10 to 15 cm from the ground to promote its germination and renewal. 3. Severe freezing injury (the aboveground part or even the root system is frozen): truncating and sprouting, or replenishing seedlings with container seedlings, and replanting cold-tolerant eucalyptus varieties or other tree species. (1) Technical methods of freezing injury investigation reference standard for evaluation of frost injury grade of eucalyptus: survey was conducted according to typical sampling methods, and then statistics were made on the frost injury of eucalyptus species and clones. Grade 0: there is basically no frost injury, and the tender and slightly wilted young leaves suffer frost injury and can grow normally. Ⅰ grade: the main stem is frozen and withered less than 50cm, some branches are damaged by freezing, most of the leaf tips are frozen and withered, and the death rate of the whole leaf is less than 30%. Ⅱ grade: main stem freeze-withered 1pm less than 3, 1-year-old branches withered less than 1pm, leaf withered rate less than 70%. Ⅲ grade: main stem freeze-dry 1pm 1pm 2, 1-year-old branches withered, 2-year-old branches freeze-damaged, leaves withered, can resume growth. Ⅳ class: main stem freeze-dry 1-pound 2-pound 3, 1-year-old branches withered, 2-year-old branches withered 60%, crown withered, it is difficult to restore growth. Ⅴ: all the aboveground parts were frozen and withered, only the base of the trunk was not damaged. (2) Technical measures for emergency rejuvenation: 1. To cut off or remove the frozen dead part of the plant. Eucalyptus usually does not appear the symptom of freezing to death immediately after freezing injury, so the freeze-dried parts of Ⅱ and Ⅲ eucalyptus should be cut off so that they can sprout and grow normally again. For freeze-damaged Ⅳ eucalyptus, cut dry at a distance of 10-15 cm from the ground to promote its germination and regeneration. For Ⅴ grade eucalyptus suffering from freezing injury, stem cutting and sprouting renewal can be carried out, or container seedlings can be used to replace cold-tolerant eucalyptus varieties or other tree species. For slight freezing injury (Ⅰ grade), it will not have much effect on the growth of the following year, as long as it is managed according to the routine and pay attention to keep the top strong lateral buds. 2. Strengthen the management of tending. When the sprout strip grows to about 40 cm, keep 1-2 strong sprout strips, loosen the soil, apply calcium magnesium phosphate fertilizer with boron or special fertilizer for eucalyptus, and pay attention to observation and control of diseases and insect pests.