The symptoms were mainly on the young leaves of new shoots. At first, the mesophyll turned yellow, but both sides of the leaf veins remained green, resulting in the loss of green on the leaf surface in the shape of green reticulate. With the development of the disease, the degree of Leaf Chlorosis increased, the whole leaf turned yellow, the leaf edge withered and scorched, causing defoliation. When there is a serious iron deficiency, the top of the new shoot withers.
The pathogen is caused by iron deficiency. Because iron is difficult to transfer in plants, iron deficiency mostly starts from the young leaves at the top of new shoots. Iron can catalyze the synthesis of chlorophyll, and iron is one of the components of respiratory enzymes. When iron is deficient, chlorophyll synthesis is inhibited, and plants show chlorosis, yellowing and even albinism.
In terms of the iron content of the soil, the general soil is not iron deficient, but in the heavily saline soil, the soluble divalent iron is transformed into insoluble trivalent iron, which can not be absorbed and utilized by plants, so it shows iron deficiency. It can be said that all factors that aggravate the degree of soil salinization can aggravate the performance of deficiency symptoms. For example, in case of drought, the evaporation salt of groundwater concentrates on the soil surface; In the depression with high groundwater level, salt accumulates on the surface with groundwater; The soil is sticky and poorly drained, which is not conducive to the leaching of salt to the lower layer with irrigation water, and yellow leaf disease is easy to occur.
The fundamental measure to control yellow leaf disease is to improve soil and release fixed iron; Proper supplement of soluble iron can treat yellow leaf disease.