Prevention and Control of cracking Disease of growing Apple

The occurrence of fruit crack disease in the later stage of apple growth is common and the harm is serious, which seriously affects the commercial value of apple, which should be paid enough attention. Apple crack disease is a physiological disease caused by the slow expansion of pulp cells in the early stage of apple growth and the rapid expansion of rain cells in the middle and later stages of apple growth. the degree of the disease is closely related to variety, tree age and tree potential. The disease of Fuji variety is more serious, the tree age is older, the tree potential is weak and heavy, the tree age is young, and the tree strength is less and light.

I. the cause of apple crack disease

1. Environmental conditions

Abrupt changes in orchard environment such as drought, high temperature and windy during apple growth and development are the direct causes of cracking disease. The continuous drought in spring, especially after many days of high temperature and drought in the young fruit expansion period, sudden showers, high rainfall intensity, short duration, sunny days after rain, and continuous high temperature will lead to the occurrence of apple crack disease. The fruit expansion period is the critical period for fertilizer and water demand of fruit trees. in case of drought and high temperature weather and no timely irrigation and water supply, it will seriously affect the pericarp cell development and lead to out of sync with the pulp tissue development. If there is sudden precipitation or artificial irrigation before harvest, it is easy to cause water absorption and expansion of pulp cells, tear of cortical tissue and form fruit surface cracks. Most of the cracks occurred in the period of rapid expansion or near ripening of the fruit.

2. Soil conditions

The soil nutrition condition of orchard is closely related to the occurrence of apple crack disease. Cracks rarely occur in orchards with high content of soil organic matter and balanced nutrients. The contents and changes of calcium, boron, nitrogen and potassium in soil are directly related to the occurrence of cracks. When the content of calcium and boron in the soil is insufficient, or the content of nitrogen is too high, the apple crack disease is aggravated. The application of boron fertilizer and calcium fertilizer and potassium fertilizer in the soil are helpful to alleviate the occurrence of the crack disease. The soil nutrient and water supply of the long-term grassy orchard was balanced, and the occurrence of crack disease in the orchard was lighter than that in the clear-ploughed orchard.

3. Cultivation and management

Extensive orchard management, closed canopy, poor ventilation and light transmission of the inner chamber led to the unsound development of the cuticular layer of the pericarp, the decrease of elasticity and the serious occurrence of crack disease. The sunny side of the fruit is usually evenly colored and rarely cracked, while the shady side of the fruit is easy to crack, especially in the shady area adjacent to the two fruits, which often becomes the concentrated area of cracks. Bagged fruit is also prone to crack in rain or extreme dry and hot weather after taking off the bag.

II. Prevention and control measures

1. Strengthen water management in orchards.

Strengthening orchard water management is an effective measure to slow down the occurrence of crack disease. Conditional orchards should be irrigated once in winter or early spring, and pay attention to irrigation during the fruit expansion period, so as to maintain stable soil water content and make the fruit grow evenly. In places with poor water sources, orchard grass growing and water-saving irrigation techniques, such as grass-covered drip irrigation and grass micro-spraying, should be carried out to regulate the supply of soil water and nitrogen.

2. Strengthen soil management in orchards.

Pay attention to the application of organic fertilizer and balanced fertilization in orchard, spraying boron fertilizer once in flower bud stage, spraying boron fertilizer before bagging in young fruit stage, adding calcium supplement twice.

3. Attach importance to the comprehensive cultivation and management of orchards. The incidence of dwarfing rootstocks is significantly higher than that of Arbor trees. In cultivation, dwarfing trees should be deeply buried in rootstocks, re-pruned and rejuvenated. When bagging, reduce the use of single-layer low-quality paper bags, choose high-quality double-layer tricolor paper bags, especially dry areas can also choose paper plus film bags. When bagging, the mouth of the bag must be tied tightly, and Rain Water's smooth fruit handle should not be allowed to flow into the fruit bag. At the young fruit stage, use as few pesticides that are irritating to the pericarp cells. Timely picking leaves, turning fruits, and laying reflective film on the ground to replenish light to promote the sound development of pericarp. Optimize the tree shape, remove too many branches, open the interlayer light path, reduce the crown area with low light efficiency, and create favorable conditions for uniform coloring of fruits. Avoid hot, windy, hot and hot weather when taking off the paper bag. Plastic bag fruit, harvest, storage and transportation with bag.