Eucalyptus is widely used as a street tree in urban areas and for garden landscaping due to its elegant shape, lush green foliage, and evergreen nature. However, it has specific environmental requirements. Eucalyptus prefers acidic soil and is sensitive to alkaline conditions. It also has low cold tolerance and is prone to pests and diseases. One of the most common issues faced by eucalyptus is yellowing disease, also known as chlorosis.
Yellowing disease is a physiological disorder caused mainly by iron deficiency. Eucalyptus seedlings thrive in acidic environments, but if they are planted in alkaline soil for a long time, their roots struggle to absorb essential nutrients like iron, leading to leaf discoloration. The leaves turn yellow or even pale white, especially along the veins. This condition is more prevalent in northern China, where the soil and water tend to be alkaline. In recent years, with the expansion of urban construction and the transformation of old cities, construction waste and harmful substances have entered the soil, altering the original soil structure that was suitable for eucalyptus growth. This change has further increased the occurrence of yellowing disease.
The symptoms of eucalyptus yellowing disease typically start at the top of the tree, affecting new leaves more severely than older ones. Affected leaves lose their green color, develop white or milky spots, and in severe cases, may become necrotic. The condition tends to worsen during winter and spring, when the tree's metabolic activity slows down, making it harder for it to absorb nutrients.
To address this issue, it's important to adjust the soil pH to make it more acidic, which helps improve iron uptake. You can apply sulfur powder to the soil, or use a diluted ferrous sulfate solution (1:20) around the root zone. Another effective method is trunk injection, mixing 15 grams of ferrous sulfate, 50 grams of urea, and 5 grams of magnesium sulfate in 1 liter of water. Spraying the leaves with a 0.1–0.2% ferrous sulfate solution can also help restore the plant’s health. These treatments should be applied regularly, especially in areas where soil conditions are unfavorable for eucalyptus growth.
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