Scientific management of lemons is the key to achieving high yields

Summer is the period when lemon young fruits swell, summer shoots emerge and physiological fruit drop occurs, and it is the key season for ensuring lemon yield and improving lemon quality. The main summer management techniques for lemons include the following aspects:

1. Soil, fertilizer and water management

1. Water management. Because there is more rain in summer and sustained high temperatures, orchard humidity is too high, so orchard drainage should be strengthened in time, and drainage ditches and back ditches should be properly prepared. The depth of the drainage ditch depends on the terrace position of the soil: for dry-field ditches, the depth is 70-80cm and the width is 60cm; for first-terrace and second-terrace soil, the ditch depth is about 40cm and the width is about 30cm. If drought occurs and the soil moisture content is below 60%, irrigation should be carried out immediately to ensure sufficient water supply during the young fruit stage. If the water source is insufficient, water-saving hole irrigation can be used, and straw and rice straw can be used to cover the tree base to increase humidity and lower temperature.

2. Apply fruit-strengthening fertilizer. Determine the fertilization time according to weather conditions, and determine whether to increase or decrease the amount of fertilizer according to the soil fertility and tree vigor.

Apply from late June to before July 20. For trees with a current-year yield within 25kg, apply 2kg of lemon special fertilizer + 80-100kg of human and livestock manure water per tree. For every additional 10kg of yield, apply an additional 0.5kg of special fertilizer.

2. Summer pruning

For adult fruiting trees: first, promptly remove summer shoots to avoid shoots competing with fruit for nutrients and reduce secondary physiological fruit drop; second, prune out weak branches, diseased and pest-infested branches, densely growing branches and water sprouts to ensure ventilation and light penetration inside the tree canopy; for some old and weak trees with few fruits, prune moderately and heavily before the summer solstice and strengthen fertilizer and water management; for young trees, pinch the tips to promote canopy expansion and train the trunk and shape the tree.

3. Pest and disease control

In summer, the main pests and diseases occurring on lemons include red and yellow spider mites, arrowhead scale, rust mites, anthracnose, scab, etc.

1. Red and yellow spider mites

Red and yellow spider mites mainly damage leaves. Red spider mites cause small grayish-white spots on damaged leaves, and in severe cases the entire leaf becomes grayish-white and defoliation is caused; yellow spider mites cause large yellow patches protruding toward the leaf surface on both sides of the main vein and between the main vein and branch veins of damaged leaves, and can cause leaf deformity or shedding. The damage is relatively severe, so control should be carried out well.

Control agents: ① 24% Weiman emulsifiable concentrate 4000-6000 times liquid (can only be used once a year); ② 20% Saomanjing emulsifiable concentrate 2000-3000 times liquid; ③ 5% Nisuolang emulsifiable concentrate 1000-1500 times liquid; ④ 20% Simanqin emulsifiable concentrate 2000 times liquid; ⑤ 0.3% azadirachtin emulsifiable concentrate 1000-1500 times liquid; ⑥ 45% crystal lime sulfur mixture 250-400 times liquid.

Choose any one of the above agents and spray evenly after diluting with water.

2. Lemon arrowhead scale

Lemon arrowhead scale damages lemon leaves and branches, causing leaf yellowing and shedding, and in severe cases branch death; it damages fruit, causing yellow spots and affecting the appearance quality of the fruit. When damaged dead branches appear, they should be pruned in time and burned in a centralized manner. For lightly infested orchards, carry out spot treatment; for heavily infested orchards, treat the whole orchard. In especially severe cases, control can be carried out 2-3 times consecutively. The first suitable control period is May 17-20; the second suitable control period is May 29-June 1; the third suitable control period is June 13-18.

Control agents: ① 3% Nianfeng emulsifiable concentrate 1500-2000 times liquid; ② 0.5% Guosheng emulsifiable concentrate 800-1000 times liquid; ③ 48% Lesiben emulsifiable concentrate 1500 times liquid; ④ 40% Julei 1000-1500 times liquid; ⑤ 0.5 Baume degree lime sulfur mixture spray (used in June); ⑥ 25% Pujiling wettable powder 1500-2000 times liquid.

Choose any one of the above agents, add Xingao Zhimo, dilute with water and spray evenly.

3. Lemon rust mite: mainly damages lemon leaves and fruit, causing gray fruit or black fruit. The suitable control period is from June to August. Strengthen inspection of lemon orchards. When one gray fruit (black fruit or newly damaged leaf by rust mite) is found in the whole orchard, apply pesticide immediately for control.

Control agents: ① 10% Anximan suspension concentrate 1500-2000 times liquid; ② 20% Saomanjing emulsifiable concentrate 2000-3000 times liquid; ③ 20% Simanqin 2000 times liquid; ④ 0.5 Baume degree lime sulfur mixture.

Choose any one of the above agents, add Xingao Zhimo, dilute with water and apply for control.

4. Lemon anthracnose and scab

Under conditions of more rain, it is easy to induce anthracnose and scab, causing fruit drop. In summer, attention should be paid to drainage to reduce field humidity; pick up fallen fruit in the orchard and burn it in a centralized manner to reduce the pathogen base; carry out chemical control of anthracnose and scab well. While controlling arrowhead scale, combine with the application of disease-control agents, with an application interval of 10-15 days, applying continuously 3-4 times, and alternate the use of pesticides.

Control agents: ① 10% Shigao water-dispersible granules 3000 times liquid (therapeutic agent); ② 18% Baozhida emulsifiable concentrate 800-1000 times liquid (therapeutic agent); ③ Hushu Jiangjun; ④ 25% Shibaoke emulsifiable concentrate 1000 times liquid (therapeutic agent); ⑤ 12% myclobutanil 2000 times liquid (therapeutic agent); ⑥ 70% thiophanate-methyl wettable powder 600-800 times liquid (therapeutic agent); ⑦ 80% Dacheng M-45 wettable powder 600-800 times liquid (protective agent); ⑧ 80% mancozeb wettable powder 600 times liquid (protective agent); ⑨ 0.5 Baume degree lime sulfur mixture (used after mid-June).

Choose any one of the above agents and apply for control after diluting with water.

4. Lemon bagging technology

1. Bagging time: Spring-flowering lemon fruits should be bagged from late June to mid-July; summer-flowering fruits should be bagged from August to September. After bagging, the growth time of lemon fruit must be guaranteed for 70-90 days.

2. Selection of fruits for bagging: Choose fruits with good early-stage pest and disease control, smooth fruit surface, good fruit shape, no disease or pest spots, and fruit diameter of about 35mm for bagging.

3. Selection of paper bags: Choose opaque wood pulp paper bags with 50g outer paper and 40g inner paper. They are required to have good moisture resistance, tensile strength and permeability, not be soaked when alcohol is dripped on the surface, not rot when rubbed in water, not spread when water is dripped on the surface, have pre-embedded tying wire, and after inserting a fist into the fruit bag and looking from inside to outside against the light with the naked eye, there should be no sand holes.

4. Bagging method: "one open, two cover, three gather, four twist": first open the paper bag with a fist, then put one fruit into one paper bag, and place the fruit in the middle part of the bag, with the bag opening level * at the fruit stalk, gather the bag opening, and use the tying wire pre-embedded at the edge of the fruit bag to twist around the fruit stalk to seal the opening.

5. Precautions for bagging: 1-2 days before bagging the fruit, spray the tree body and fruit surface uniformly and thoroughly once with insecticide and fungicide. After the pesticide on the fruit dries, bagging can be carried out; if lime sulfur mixture is applied, bagging should be carried out 5-7 days after application to avoid fruit burn; fruits not treated with pesticide cannot be bagged, those with poor early-stage pest and disease control cannot be bagged, those with pesticide solution not yet dry cannot be bagged, those with dew not yet dry cannot be bagged, bagging cannot be done on rainy days, and bagging cannot be done during high temperatures at noon. The paper bag opening should face downward. After bagging, if drought occurs, irrigate in time and cover with straw.