Occurrence of damage: at first, the impact on the yield and quality of diseased trees was not obvious, and the development was slow. Therefore, cultivators do not know enough about its harm. In fact, after the disease of 1 susceptible varieties, the annual branches of 1 are shorter than those of healthy branches, the number of nodes is reduced, the general good fruit rate is reduced, the diseased fruits are not resistant to storage, and the diseased trees often fall off their leaves early, which easily leads to other diseases and losses to production. The yield of diseased trees was reduced by 55%(PosnetteandCropley, 1956,1959; Woodtal. , 1975)。 In recent years, due to a large number of susceptible varieties such as Qin Guan and Jin Guan, the distribution of the disease is expanding day by day through the spread of infected seedlings. In Guanzhong and Weibei areas of Shaanxi Province, the rate of diseased plants in some orchards is as high as over 30% (Wei Ningsheng, 1960).

At present, apple mosaic disease is still spreading widely, which harms all aspects of fruit tree production and scientific research. For example, the dwarf rootstock nursery imported from abroad in the study of dwarf apples has mosaic disease; Dwarf rootstocks introduced at home and abroad are grafted on big apple trees, and the rapidly propagated scions have mosaic disease; The newly-built dwarf apple orchard has mosaic disease; Introducing newly cultivated apple varieties and grafting them on big apple trees will cause mosaic disease; In the selection of apple bud mutation, there is mosaic disease when the new bud is grafted on the big apple tree; In the selection of apple bud mutation, new buds are grafted on big apple trees to cultivate mosaic disease; Mosaic disease occurred in many orchards in the scion nursery of short-branch Red Fuji. Mosaic disease can also be seen everywhere in large-scale apple production. In a word, mosaic disease is affecting apple production, even seriously hindering fruit tree scientific research to obtain correct results, and even destroying scientific research results.

Mosaic disease not only harms apple, bonus, begonia, sand fruit, betel nut, hawthorn and other fruit trees, but also harms pear, papaya, quince and so on.

Mode of transmission: No natural media found. The main route of transmission is the input of Rubus plants and propagation materials. The virus only spreads through scions or rootstocks. It is difficult to spread the virus from apple leaves to herb juice, but it is a little easier to use apple petals. The disease spreads slowly in the orchard, and most of it is infected by root grafting.

Vector: None.

Seedling-borne plants: apple asexual propagation materials and cowpea seeds (gotlieb &; Bobby 1973).

Natural hosts: Crabapple, Crabapple, Crabapple, Crabapple, Crabapple, Crabapple, Ginkgo biloba (Wei Ningsheng, 1960), Aesculus chinensis, Aesculus rubra, Birch, Broussonetia papyrifera, Papaya, Corylus heterophylla, Humulus Humulus, Prunus armeniaca, Prunus mume.

Infective plants were artificially inoculated: plum in Tang Di, papaya in Japan, apple in Huaxi, hawthorn in Britain, cucurbitacin, cucurbitacin, loquat, osmanthus fragrans, Vitex negundo, wild apple, Xifu apple, apple, Malus yunnanensis, Malus yunnanensis, mung bean, Sorbus sorbus, Sorbus pallens, Cynanchum, Catharanthus roseus, etc.

Infection cycle: after the apple tree is infected with mosaic virus, the whole tree is infected with the virus, which constantly proliferates and harms life. Shortly after the diseased trees germinated in early spring, diseased leaves appeared. The mottled symptoms observed in Guanzhong area of Shaanxi Province mostly appear after apple germination 10 ~ 20d ~ 20d. The lesion developed rapidly from early April to early May, and then slowed down sharply. In the midsummer of July and August, the disease basically stopped developing and even appeared recessive. After the diseased trees sprouted in autumn shoots in early September, the symptoms began to develop again, slowed sharply in June at 5438+ 10, and stopped completely in June at 165438+ 10. As a result, some diseased branches only have lesions in the basal and parietal leaves, while the middle leaves have no lesions. Some diseased leaves began to turn yellow and died in mid-June. After the end of May, seriously ill trees began to shed their leaves early, with an average yield reduction of about 30%. Mosaic trees are also easy to cause apple fungi to shed leaves, and the fruits of diseased trees are not resistant to storage. The average growth of new shoots of seriously ill trees decreased obviously, especially in autumn shoots.

In addition to apple mosaic virus, Tula apple mosaic virus and plum necrotic ringspot virus also have apple mosaic virus strains. Whether the latter two viruses exist and distribute in China remains to be studied.

Disease, environment and epidemic: Apple mosaic virus is mainly transmitted by grafting. Scions or rootstocks are toxic and are the main source of infection. The incubation period of the disease is 3 ~ 27 months. The length of incubation period is mainly related to the grafting period and the size of experimental materials.

The occurrence of apple mosaic is greatly influenced by environmental conditions and the growth of host plants. When the air temperature is 10 ~ 20℃, the light is strong, the soil is dry and the tree is weak, which is beneficial to the occurrence and spread of diseases. There are also obvious differences in the susceptibility of different apple varieties. Its highly susceptible varieties are Bailong, Qinguan, Jinguan, Wojin, Huang Kui, Ganlu, Shengniang (hibiscus skin) and so on. Mildly susceptible varieties include Hongyu, Jiugui Lu, Hongkui, Feiyi, Hongxing, Marshal and Guoguang. The resistant varieties are Zhuguang, Indian, Gan Shengxu, Dahongshan and Jinying (Wei Ningsheng, 1960).