Common Causes of Citrus Yellowing and Treatment Options

Yellowing disease is one of the most common pathological symptoms of citrus. It is generally manifested as chlorosis and yellowing of large leaves of fruit trees, reduced photosynthesis ability, and poor ability to absorb water and fertilizer, which will affect fruit yield and quality in light cases, and cause fruit trees to wither and die in severe cases. Yellowing disease is caused by a variety of reasons, such as root problems, improper girdling, overuse of hormones, pests and diseases, etc.

1. Reasons for citrus yellowing

Citrus yellowing disease is mostly caused by root damage caused by improper management, soil problems, natural disasters, pests and diseases, etc., which in turn leads to a systemic lack of nutrient supply. It is repairable and can be improved through defense and governance.

1.1 Nutritional deficiencies

Plant growth requires 16 kinds of nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium. Once one of the nutrients is insufficient, yellowing will occur. The diagnosis of nutrient deficiency depends on whether the yellowing of nutrient deficiency occurs in the old leaves or in the new leaves, and then to see whether the size of the leaves is normal. When the crop is deficient in nutrients, it is necessary to make up for the deficiency and balance fertilization. According to statistics, for every 1000kg of citrus fruits produced, 6kg of nitrogen, 1.1kg of phosphorus, 4.8kg of potassium, 0.8kg of calcium and 0.27kg of magnesium are required. The ratio of nitrogen, phosphorus and potassium is 1:0.2:0.8.

1.2 Root problem

After damage to the citrus root system, the ability of plants to absorb mineral nutrients and water, and to synthesize hormones is drastically reduced, which will eventually lead to abnormal leaves. The main causes of root problems mainly include the following ones.

1.2.1 If the circumcision is excessive, the nutrient transport system of fruit trees is damaged, and the photosynthetic products and energy of the above-ground leaves cannot be transported to the ground, resulting in root necrosis, unable to absorb mineral nutrients and complete water transport.

1.2.2 The yield is too heavy and the root nutrition is overdrawn, which leads to yellowing in the following year and the tree body is weak.

1.2.3 Improper fertilization leads to root rot and necrosis, causing citrus yellowing or even death.

1.2.4 Improper use of pesticides, which are absorbed and conducted internally, damage the roots, and lead to yellowing and death.

1.3 Soil problem

1.3.1 The soil is slightly acidic or alkaline, which affects the activity of mycorrhiza, weakens the absorption capacity of citrus roots, and causes nutritional yellowing of leaves.

1.3.2 The organic matter content in the soil is low, and the medium and trace elements are deficient.

1.3.3 The soil is sticky or compacted, which affects the gas exchange and absorption on the surface of the root system, prevents excess water from infiltrating, and causes composting of roots.

1.3.4 Unbalanced water in the soil. Excessive soil moisture and stagnant water can easily lead to root rot, and plants cannot get enough water and nutrients, causing leaves to turn yellow, leaves to fall, and fruit drop. On the contrary, when the soil moisture is too low, the soil nutrients cannot spread to the root system with the movement of water, resulting in dehydration and drought damage. For the problem of soil moisture imbalance, the best prevention and control measures are to improve the drainage system, dig trenches for drainage according to the terrain, and irrigate in time when drought occurs.

1.4 Climate disasters

Common climatic disasters are floods, droughts, and frost damage. The prevention measures are to do a good job of preventing cold and freezing, and prune the immature branches before freezing.

1.5 Yellowing caused by pests and diseases

Citrus diseases and insect pests will also damage the tree to a certain extent, affecting the normal transport of nutrients, resulting in yellowing of leaves.

2. Citrus yellowing treatment

2.1 Soil improvement: increase organic matter, adjust pH, improve soil structure, and allow drainage and ventilation.

2.2 Strong root: Promote root growth, protect root health, and ensure root nutrition.

2.3 Supplementary nutrition: attach importance to soil nutrient supplementation, balance nutrient fertilization, and promote nutrient absorption.

3. A overall solution for citrus yellowing

3.1 Apply base fertilizer. Combine organic fertilizer, compound fertilizer and trace element fertilizer as base fertilizer.

3.2 Apply biochemical fulvic acid to provide nutrients for plants + apply mineral source humic acid to improve soil, chelate nutrients + pay attention to root nutrition and foliar nutrient solution, apply organic fertilizer, water-soluble fertilizer, and trace elements.