What are the control methods for apple boron deficiency?

Apple boron deficiency is a physiological disorder caused by boron deficiency, and in the past two years it has shown a worsening trend on early-maturing apple varieties such as American No. 8 and Gala, and late-maturing varieties such as Qinguan.

1. Symptoms:

The main symptoms on the fruit can be divided into three types: dry spot type, corky type and rusty spot type.

1) Dry spot type: symptoms appear early, mostly in the early stage of young fruit development. At first, dark green or dark red water-soaked spots appear on the fruit surface, the flesh turns brown to dark brown, gradually necroses, and the affected part shrinks, hardens, sinks and becomes deformed. Severely affected fruit becomes smaller or cracks at the dry spots and tends to drop early.

2) Corky type: mostly occurs in the later stage of fruit growth. Water-soaked small spots appear in the flesh of the affected fruit, usually spreading along the core line and distributed in strips; the flesh turns brown and becomes spongy. The appearance of the affected fruit changes little, only the fruit surface becomes uneven, and it feels soft when pressed by hand. When the disease occurs at the young fruit stage, the fruit becomes smaller and deformed and tends to drop early. When the fruit is infected in the later stage of growth, the fruit surface becomes uneven. Red varieties color early and tend to drop early; most severely affected fruit becomes spongy and inedible; lightly affected fruit has locally discolored and necrotic flesh, is bland in taste and poor in quality.

3) Rusty spot type: symptoms mostly appear on varieties such as Delicious. After infection, the fruit becomes flat-round or long-cylindrical, and brown, fine, dense horizontal stripes appear on the fruit surface around the stalk. These stripes often crack, the fruit surface has no necrotic lesions, and the flesh is soft.

In severe cases, this disease also appears on shoots. The symptoms are: in summer, shoot tip blight occurs, and new shoots gradually dry from the top downward. Sometimes affected branches do not sprout in spring or die rapidly after leafing out, and many fine clustered branches grow below the dead branches.

2. Cause analysis:

Boron is an essential trace element for plant cell division and tissue differentiation and plays an important role in promoting the reproductive process of fruit trees. When the boron content in the soil is low (less than 10mg/Kg), boron deficiency symptoms appear. The main causes of boron deficiency are:

1) Poor weather in early spring, excessively dry and compacted soil, and poor root development of fruit trees affect nutrient uptake, causing boron deficiency.

2) Excessive application of nitrogen fertilizer increases the growth of fruit trees, thereby increasing the demand for boron, but the boron supply cannot keep up, causing boron deficiency.

3) Barren soil or alkaline soil is prone to boron deficiency.

4) Varieties differ greatly in their sensitivity to boron deficiency. Varieties such as American No. 8, Gala and Qinguan are more severely affected.

3. Control methods

1) In combination with autumn fertilization of fruit trees, apply the medium and trace element fertilizer Dazhanggui. Application rate: for fruit trees in full bearing period, about 20 jin per mu (0.7 jin per tree); reduce the amount for young fruit as appropriate. Dazhanggui is a medium and trace element fertilizer containing boron, iron, zinc, manganese, magnesium, sulfur and other medium and trace elements. It can not only control apple boron deficiency, but also control little leaf disease, yellow leaf disease and bitter pit, promote fruit expansion and coloring, increase yield and improve quality.

2) Foliar boron spraying: spray once each before flowering, during flowering and after flowering with Gaile boron at 1500-2000 times, or Kading boron at 1000-1500 times, and at the same time add Aiduoshou at 4000 times solution to promote the corrective effect.

3) Strengthen water and fertilizer management. Apply more organic fertilizer, improve the soil, and irrigate promptly during drought.