What Causes Leaf Curling in Mandarin Oranges? Plus the Latest Control Methods
Leaf curling in mandarin oranges is a fairly common phenomenon in winter and spring. Many fruit growers encounter this situation, and some farmers, not knowing where to start, miss the best period for control, resulting in undesirable losses. Below, the editor brings you the causes of leaf curling in mandarin oranges as well as control measures. Come and learn about them with the editor.
1. Environmental factors
Spring is rainy, and when orchards are located in low-lying areas, there is a lot of standing water on the ground and excessive water content in the soil, which causes poor root respiration in mandarin oranges, thus affecting the roots' absorption of water. Over time, the leaves curl and turn yellow due to water loss.
Control method: Dig drainage ditches deep, keeping the drainage ditches more than 80 cm from the ground surface, to reduce soil water content, then loosen the soil to increase oxygen content. At the same time, cover the soil surface around the tree roots with rice straw or crop stalks to reduce rainwater erosion of the soil surface at the roots and lower root damage. Finally, spray the leaves with brassinolide to improve stress resistance.
2. Pests
Aphids harm new shoots, causing an insufficient supply of nutrients, which in turn affects the leaves, making them turn yellow and curl. In addition, summer and autumn are the peak periods for red spider mites, which harm leaves, new shoots and fruit, causing leaves to turn yellow and fall off.
Control method: For aphid damage, acetamiprid or other sprays can be used to protect new shoots. For red spider mites, saomanjing or kelmante can be sprayed to control them.
3. Nutrient deficiency
The biggest cause of yellowing, thinning and curling leaves in mandarin oranges is nitrogen deficiency. Nitrogen deficiency mainly occurs on old leaves, while new leaves are better; the leaves turn yellow overall. In the early stage of nitrogen deficiency, the leaves become pale green and then turn yellow. In addition, maintaining insufficient nitrogen fertilizer can further cause iron deficiency in mandarin oranges.
Control method: Strengthen management and increase the application of organic fertilizer. If the deficiency is severe, foliar fertilization can be used in combination, spraying a low-concentration urea and monopotassium phosphate fertilizer solution once every 10 days, and borax can be added to the fertilizer water. If there are symptoms of iron deficiency, add other elements as well. If the nutrient deficiency is caused by root damage, while supplementing fertilizer through the leaves, pay attention to caring for the root system of the mandarin orange.
4. Improper management
When forcing flowers the previous year, spraying leaves with overly high concentrations of foliar fertilizer, plant growth regulators, insecticides and so on causes certain damage to the leaves and can also cause leaf curling the following year.
Control method: Rice straw can be used to cover the roots to prevent sunlight from damaging the root system. Suspend root fertilization, and after the new shoots mature, adopt the principle of frequent but light fertilization to promote root growth. After the new leaves unfold but before they turn dark green, spray foliar fertilizer so that both roots and leaves absorb nutrients together and promote recovery of tree vigor.
The above is an introduction to the causes of leaf curling in mandarin oranges and the control methods. We hope it can help you. To learn more related knowledge, please stay tuned to us.