The Role, Timing and Method of Whitewashing Fruit Trees Explained in Detail

I believe quite a few friends have often seen that the trunks of street trees along roadsides, landscaping trees in parks, and fruit trees in orchards are painted with a white layer for a period of time.So what is the effect of whitewashing fruit trees? When should whitewashing be done? How should it be done?

What is the effect of whitewashing fruit trees?

1. Killing pathogens.

The quicklime and salt in the whitewash both have sterilizing and disinfecting effects, and can eliminate various pathogens overwintering at the base of the trunk. After whitewashing, it can also accelerate wound healing.

2. Killing insect eggs.

Many insect eggs like to overwinter in the cracks of bark, inside the loose bark of the trunk, and in the tunnels of longhorn beetles. Whitewashing can effectively eliminate these insect eggs.

3. Controlling pests.

Pests that harm fruit trees generally like dark, dirty places and do not like white, clean places. After the trunk is whitewashed, pests dare not climb up the trunk along it to harm the tree.

4. Preventing livestock.

After the trunk is whitewashed, it can also prevent the bark from being bitten and damaged by animals.

5. Preventing freezing damage.

From the beginning of winter to the following spring, the temperature difference between day and night is large. Through whitewashing, the abundant sunlight and ultraviolet rays during the day can be reflected away, reducing the day-night temperature difference at the base of the trunk and avoiding freezing damage. Because the temperature at the base of the trunk accumulates more slowly in whitewashed trees, bud break and flowering are often delayed, which can avoid frost damage caused by a “late spring cold snap.”

6. Preventing sunscald.

After the trunk is whitewashed, the bright sunlight and ultraviolet rays during the day can be reflected away, effectively reducing the occurrence of sunscald damage.

When should fruit trees be whitewashed?

Generally, whitewashing of fruit tree trunks is carried out after the fruit is harvested and before the Beginning of Winter. Whitewashing fruit tree trunks has the effects of resisting cold, keeping warm, and killing pests and diseases. This is especially true for fruit trees in full fruit-bearing stage.

How should fruit trees be whitewashed?

1. Copper sulfate and lime whitewash

A. Copper sulfate 10 kg, quicklime 200 kg, water 600-800 kg.

B. Preparation method:

(1) Use a small amount of boiling water to fully dissolve the copper sulfate, then add two-thirds of the water amount to dilute it.

(2) Add the remaining one-third of the water to the quicklime and let it slowly slake into a thick lime milk.

(3) When the above two liquids are fully dissolved and at the same temperature, pour the copper sulfate into the lime milk and stir continuously until evenly mixed.

(4) Suitable for fruit trees such as peach, plum, pear, apple, and Chinese bayberry.

2. Lime and sulfur whitewash

Preparation method:

(1) Quicklime 100 kg, sulfur 1 kg, salt 2 kg, animal and vegetable oil 2 kg, hot water 400 kg.

(2) The quicklime in the ingredients should be white in color, light in quality, and free of impurities. The finer the sulfur powder, the better.

(3) First use hot water at 40-50 degrees to dissolve the sulfur powder and salt separately, and add a small amount of washing powder to the sulfur powder liquid.

(4) Slowly put the quicklime into boiling water at 80-90 degrees and stir slowly to fully dissolve it.

(5) Fully mix the lime milk and sulfur milk, and add the salt and oil and stir thoroughly until evenly mixed.

(6) Suitable for fruit trees such as peach, plum, pear, apple, Chinese bayberry, and citrus.

3. Lime-sulfur mixture and quicklime whitewash

A. Proportioning method: lime-sulfur mixture stock solution 0.5 kg, salt 0.5 kg, quicklime 3 kg, appropriate amount of oil, water 10 kg.

B. Preparation method: add water to the quicklime to slake it, add oil and stir, then add water to make lime milk, then pour in the lime-sulfur mixture stock solution and salt water and stir thoroughly until evenly mixed.

Suitable for fruit trees such as peach, plum, pear, apple, Chinese bayberry, and citrus.

4. Lime and yellow mud whitewash.

A. Proportion: slaked lime 100 kg, yellow mud 120 kg.

B. Preparation method. Mix the slaked lime and yellow mud with water and stir into a slurry, then it is ready to use. An appropriate amount of insecticide can be added to also control overwintering pests on the trunk.

Suitable for fruit trees such as pear, apple, Chinese bayberry, and citrus.

5. Precautions for using whitewash:

A. Fruit tree whitewash should be used as soon as it is prepared and should not be stored for long.

B. Stir evenly when using to facilitate brushing, and apply the whitewash evenly on the trunk.

C. Before brushing, remove pests on the trunk, especially galls.

D. Choose a sunny day to whitewash the base of the main trunk evenly. A whitewashing height of 1.5 m from the ground is appropriate.

E. If old trees are renewed by high grafting, to prevent sun exposure, the whitewashing position should be raised or the whole plant should be whitewashed. All of the above methods can play an effective role, and fruit growers can choose according to actual conditions.