How to manage an apple orchard in the hot and humid season? Practical experience shared

In the hot and humid season, high temperatures and high humidity create climatic conditions favorable to the outbreak and spread of pests and diseases, making this a critical period for preventing and controlling the damage they cause. At the same time, the new shoots of apple trees begin their second period of vigorous growth, and the fruit enters the swelling stage of development. Regulating tree vigor and promoting good development of the young fruit are the key management tasks of this period.

1. Strengthen fertilizer and water management

1. Reasonable topdressing  Whether to apply topdressing to apple trees should be determined according to the variety, the fruit load and the earlier fertilization situation. A topdressing of phosphorus and potassium fertilizer can be applied, mainly potassium fertilizer, with the amount depending on the tree. For medium and early maturing varieties such as US No. 8 and Gala, topdress in early July; for Red Fuji apples, apply topdressing once as far as possible from mid-July to mid-August. Since July and August fall in the rainy season, if the weather is not dry there is no need to water; apply fertilizer in combination with rainfall.

2. Foliar spraying of fertilizer  In July and August, foliar spraying of phosphorus, potassium, calcium, iron fertilizers, etc. together with pesticide application plays an important role in increasing the sugar content of the fruit, promoting coloring and reducing physiological diseases of the fruit. Commonly used fertilizers include superphosphate, monopotassium phosphate, potassium sulfate, plant ash and ferrous sulfate. In practice, monopotassium phosphate is mostly used together with calcium chloride, and it is advisable that the concentration used does not exceed 0.5% total salt concentration (the total percentage content of soluble fertilizers).

3. Orchard drainage and weeding  During the rainy season, water must not accumulate in the orchard for long periods, otherwise it affects the soil permeability of the orchard and the growth of the apple tree root system. After rainfall, drain promptly to keep the orchard soil moisture relatively stable. After watering or rainfall, hoe and loosen the soil promptly and clear the weeds in the orchard.

2. Regulate tree vigor

July and August are suitable for the vegetative growth of apple trees. In particular, young trees in the early fruiting stage and the summer and autumn shoots of mature trees with few fruits tend to grow vigorously. If not regulated, this will affect flower bud differentiation, cause nutrient loss, disrupt the tree shape and reduce fruit quality. Therefore, according to tree age, tree vigor, fruiting, etc., appropriate measures should be taken to regulate it and keep the tree growing vigorously and healthily. For vigorously growing trees, generally spray 150-00 times dilution of paclobutrazol once each in early and mid-July. For young, vigorously growing trees that have not fruited or have few fruits, a second trunk or main branch girdling can be carried out in early July. At the same time, do a good job of summer pruning, focusing on thinning out upright vigorous branches on the back, water sprouts in the inner canopy, competing branches at the branch tips and useless branches that affect light exposure, and twisting and bending the temporarily retained branches, so as to control excessive growth, improve light conditions and promote fruit development and flower bud formation.

3. Prevent apple sunscald

Affected apples show water loss and scorching on the sunny side, producing reddish-brown nearly round spots. The spots gradually expand to form dark brown lesions, surrounded by a pale yellow halo, seriously affecting the commercial value of the apples. July and August are the critical period for preventing sunscald.

1. Timely irrigation  In dry weather, irrigate immediately to reduce the occurrence of sunscald.

2. Tree dish mulching  Before high temperature and drought arrive, cover the tree dish with a 20 cm thick layer of straw, grass or wheat bran, etc., which can both preserve moisture and lower the ground temperature, preventing the occurrence of sunscald.

3. Fruit surface covering  On the sunny side of fruits prone to sunscald, cover with Paulownia leaves, castor leaves or broadleaf grass, etc., which have a larger leaf area, to reduce direct sunlight and reduce the occurrence of sunscald.

4. Sticking on white paper  On the sunny side of fruits prone to sunscald, use skin lotion to stick on a piece of white paper, which can reflect sunlight and prevent sunscald.

5. Spraying lime milk  Apply a layer of lime milk on the sunny side of the apple, which can reflect light, prevent sunburn and also sterilize.

6. Spray Meifeng from July to late August  Spray Qirui amino acid fertilizer 400 times dilution 2-3 times, with an interval of 15 days each time. This can increase drought resistance, reduce sunscald, promote fruit development, improve fruit quality and at the same time make the next year's flower buds plump.

7. Spray clear water in the evening together with pesticide application  At sunset or when the sun is slanting, spray clear water on the canopy to reduce sunscald.

4. Pest and disease control

1. Insect pest control  In this period, the control focus is on red spider mites, leaf miners, leaf rollers, apple cotton aphids, as well as ring rot, anthracnose, early defoliation disease and other pests and diseases. For the control of red and white spider mites, apply pesticides at the right time according to local temperature, rainfall and occurrence conditions. Commonly used pesticides include 1.8% abamectin emulsifiable concentrate 4000 times dilution, 5% Cascade emulsifiable concentrate 1000 times dilution, 20% clofentezine suspension 2000 times dilution, 5% hexythiazox emulsifiable concentrate or 25% fenbutatin oxide wettable powder and propargite emulsifiable concentrate 2000 times dilution, etc. Leaf miners and leaf rollers should be controlled with pesticides again in early July on the basis of prevention in May and June. Commonly used pesticides are: 25% chlorbenzuron No. 3 suspension concentrate 1500 times dilution, 1.8% abamectin emulsifiable concentrate 5000 times dilution, 2.5% Kung Fu or fenvalerate 3000 times dilution; for apple cotton aphid, use 48% chlorpyrifos emulsifiable concentrate 1000 times dilution.

2. Disease control  July and August are another critical period for preventing the damage of ring rot, anthracnose and early defoliation disease. In terms of pesticide use, systemic fungicides and protective agents should be used alternately. Generally, use protective fungicides before rain and spray systemic fungicides promptly after rain. In practice, full bagging cultivation is mostly adopted, and the control of early defoliation disease should be the focus. Generally, spray once each in mid-July, early August and late August. Effective pesticides are: Bordeaux mixture at 1:2:200-240, 50% carbendazim wettable powder 800-1000 times dilution, 70% thiophanate-methyl wettable powder 1000 times dilution, 70% or 80% mancozeb wettable powder 600-800 times dilution, 50% iprodione 1000 times dilution, 10% polyoxin 1000 times dilution, etc. Alternating Bordeaux mixture with one of the above fungicides gives good results; generally spray Bordeaux mixture once every 20-25 days. Red Fuji apple orchards should spray 3 times from June to August and stop in September to avoid affecting coloring.