What are the latest control methods for apple tree diseases?

In recent years, quite a few apple orchards have seen diseases such as early defoliation disease, fruit rot, ring rot, as well as viral fruit shrinkage disease, facial discoloration disease, and mosaic disease. Generally speaking, apple trees enter the initial fruiting stage 3-5 years after planting, enter the full fruiting stage after 6-8 years, and enter the decline stage after about 20 years. But now in many places, trees around 15 years old already show decline. Why does this happen? In our investigations, we found that there are 3 main causes of tree decline.

Poor nutritional conditions

Many orchards commonly have the problems of low soil organic matter content and insufficient application of organic fertilizer. Although in the past 2 years fruit growers' incomes have increased, their enthusiasm has risen, and they have gradually increased the amount of organic fertilizer applied, it still has not reached the proper standard, and organic nutrition is still lacking. In addition, many fruit growers still attach importance to applying base fertilizer, but topdressing is sometimes done and sometimes not, so the fruit trees cannot receive timely and adequate nutrient supply at each key growth stage.

Excessive load

Some fruit growers still have the idea of increasing income through yield, leaving too many fruits, which becomes “exploitative” production, making the tree load too heavy, the fruits too small, and the number of flowers reduced the following year, resulting in alternate bearing, early tree decline, and reduced disease resistance.

Improper application of girdling technology

To promote flower bud formation, some fruit growers carry out girdling year after year on scaffold branches and lateral branches at all levels of the tree, and the girdled strip is relatively wide, causing poor wound healing, seriously affecting the transport of nutrients produced by leaf photosynthesis to the roots, leading to poor accumulation of organic nutrients in the tree, extreme tree decline, and easy triggering of various diseases.

In addition to the above 3 main causes, improper application of training and pruning techniques, ineffective pest and disease control, drought, freezing injury, and so on can also affect tree vigor.

In response to the main causes of tree decline, the following measures need to be taken to strengthen tree vigor:

① Increase the application of organic fertilizer and carry out timely topdressing to improve the nutritional level of the tree. In autumn and winter, increase the application of farmyard manure such as decomposed chicken manure, cattle and sheep manure, and human excrement and urine, which can improve the soil, strengthen tree vigor, and improve disease resistance. The standard for organic fertilizer application is “a jin of fertilizer for a jin of fruit.”

② Keep an appropriate amount of fruit. Only by determining an appropriate fruit retention amount can stable and high yields be ensured, tree vigor balanced, and disease resistance improved. The distance flower thinning method or the trunk circumference method can be used to determine the fruit retention amount.

③ Implement ring cutting technology to replace girdling technology. To promote flower bud formation in apple trees, some fruit growers carry out girdling year after year on scaffold branches at all levels of the tree, and the girdling cut is relatively wide, causing poor wound healing, seriously affecting the transport of nutrients to the roots, leading to tree decline and triggering early defoliation disease. To strengthen tree vigor and improve disease resistance, girdling on the central leader is prohibited, and instead, multiple ring cuts are made in separate rounds on main branches, lateral branches, and branch groups, starting 15 cm above the base of the branch and using a ring-cutting knife to cut horizontally all the way around. According to branch vigor, make 1-2 ring cuts each time, with a spacing of 10 cm, and make ring cuts once every 7-10 d. When making ring cuts in separate rounds, the spacing between cuts must not be less than 3 cm. Orchards with a large and stable amount of flowering do not adopt ring cutting technology.