Etiology: Yellowing disease is mainly due to the lack of soluble iron in soil. In some areas, because the soil contains more carbonate and the soil is alkaline, the soluble iron content is low; Or because there is much rain, too much soluble iron in the soil is leached out; In the soil with heavy soil and high groundwater level, the normal physiological activities of plant roots are affected, which reduces the ability of root system to absorb iron, so plants lack available iron, which affects the formation and yellowing of chlorophyll.

Prevention and cure method

1. Lilac flowers should not be planted in alkaline soil, nor in places with low terrain and easy water accumulation, or in construction waste with more abandoned lime in old houses, otherwise the root system will be stunted and prone to yellowing.

2, the application of organic fertilizer, add some ferrous sulfate to the organic fertilizer, such as single-handed stacking organic fertilizer, can be mixed with 250 grams of ferrous sulfate. After being applied to soil, the organic acids produced during the decomposition of organic fertilizer can increase the activity of iron and make it easy for plants to absorb.

3. The diseased plants can be irrigated with 0. 1-0.2% ferrous sulfate aqueous solution. The aqueous solution of iron chelate can be applied to soil. According to the different flooding conditions of trees, about 25-100g can be applied to each tree. The seedbed uses 500 grams per 10 square meter, and it is not needed after the leaves turn green.

4. In alkaline soil, combined with fertilization and proper application of physiological acid fertilizers such as ammonium sulfate, ammonium chloride and calcium superphosphate can improve the physical and chemical properties of soil and improve the availability of iron in soil.