New techniques for prevention and control of apple ring disease

New techniques for prevention and control of apple ring disease

Apple ring disease, apple tree rot and early apple defoliation are the three main diseases of apple in China. Because of its close relationship with climate, the disease is more serious in North China, Northeast China and East China.

1 symptoms of infection

Apple ring disease mainly affects branches and fruits.

1.1 symptoms of branch disease

A dark brown, watery or small ulcer spot is formed with the lenticel as the center, the central process is tumor-like, then dehydrated, the edge is cracked and warped, and expands outward with the disease spot as the center for several years in a row, forming concentric wheel-like spots, and multiple disease spots are dense. the bark of the trunk branch is rough, also known as "rough bark" (Fig. 1-Fig. 3).

Fig. 1 Apple wheel pattern disease harms the initial symptoms of branches and stems.

Fig. 3 Apple wheel grain disease harms late branch symptoms

Fig. 4 Apple wheel grain disease harms the initial symptoms of fruit.

Fig. 2 Apple wheel grain disease harms mid-branch symptoms

Fig. 5 Apple wheel rot harms the mid-term symptoms of fruit.

1.2 symptoms of fruit disease

With the lenticel as the center, it presents water-stained near-round brown spots and spreads in all directions, forming deep and shallow concentric lines, and the lesion site in the later stage of the disease.

2 occurrence regularity

The disease overwintered on the damaged branches with mycelium, conidia and pseudocyst, and the hyphae could survive for 4-5 years in the diseased tissues. After the temperature rises in spring, the bacteria begin to release spores in case of rain and spread with the wind and rain. In the north, spores began to distribute in the first rainfall in May (after apple blossoms), and reached a peak in July and August. Rainfall and rainfall duration are important factors affecting the time and quantity of spore release. Generally, there is a spore emission peak after each rainfall (in which May rainfall is the key to affect the number of spores produced by apple ring disease in the whole year). The pathogen first infects the branches, but does not cause the disease, and only lurks in the phloem when the rainfall is more than 10 mm. When the bark is wet through more than 10 mm, the spores hidden in the trunk phloem all open and release spores; after fruit setting, there are many cork tissues in the young fruit, coupled with high acidity, high tannin content and other factors are not conducive to mycelial growth, only latent in the pericarp, non-proliferation and no disease. After the fruit is enlarged, the cork tissue in the fruit is transformed into pulp cells, and because of the low acidity, the increase of sugar content and the decrease of tannin content, the bacteria are easy to infect the fruit.

3 influencing factors

3.1 Climate

The occurrence of apple ring disease is closely related to climate. The temperature is higher than 20 ℃, the relative humidity is higher than 75% or continuous rainfall, and the rainfall is more than 10 mm, which is conducive to the reproduction of bacteria and the spread of a large number of spores, the disease will be aggravated, on the contrary, the disease is lighter in the year of drought and less rain.

3.2 varieties

There were significant differences in resistance of apple varieties to apple ring disease. Golden Crown, Fuji and Golden halo are the most susceptible, followed by Marshal, Shouhong and Guoguang are more resistant, Jin light is the most resistant.

3.3 Tree potential

Apple ring disease is a kind of weak parasitic pathogen, the disease is light if the tree is strong, on the contrary, the tree is weak and the disease is serious. Therefore, increasing the application of organic fertilizer, reasonably controlling the proportion of nitrogen, phosphorus and potassium fertilizer, scientific management and strengthening the tree potential can effectively resist the occurrence of apple ring disease.

Fig. 6 Apple wheel streak disease harms late fruit symptoms

4 prevention and control measures

After 18 years, the Plant Protection Research Office of Tangshan Academy of Agricultural Sciences in Hebei Province has conducted a long-term and systematic study on the incidence characteristics and regularity of apple ring disease, obtained breakthrough results, and proposed to change the old control concept of scraping bark before. we should change the control in spring to the control in the middle and later period, and seize the key period to focus on control. After our 3-year pilot experiment, this technique can effectively control the occurrence of apple ring disease. That is, after the first rainfall in May, all the diseased tumors hidden on the branches and the mature spores in the warped skin spread out the spores. [Jishan Huayao] then used a 400-fold spray of Wheel No. 1 special fungicide to control it. It can get twice the result with half the effort, and can protect the tree potential (at this time, the medicine is quickly used to kill the mycelium of ring disease pathogen through a large number of pores inside the bark. Help to promote the old disease bark off, no longer produce diseased bark, there is no need to scrape the bark). 400 times of the special fungicide Wheel No. 1 was sprayed before bagging, and Wheel No. 1 was sprayed again 5-7 days after bagging, while those without bagging began to use Wheel No. 1 (sprayed every 15 days) for 3 consecutive times in mid-July, and sprayed again 5-7 days before fruit picking, the control effect was more than 90%.

Therefore, fruit grower friends will no longer have to scrape the bones of fruit trees, but should focus on strengthening tree potential and prevention in the middle and later stages, adhere to scientific prevention and control, and strengthen comprehensive management. Apple ring disease can be cured.