In the 1-year growth cycle of apple trees, the resistance of the trees to rot disease is different at different times, and the occurrence of rot disease is also very different.
Latent Period
The apple tree sprouts from the spring leaves to the deciduous leaves in November, which is also the period of resistance of the apple tree to rot. During this period, tree photosynthesis, water metabolism and other physiological activities are strong, can produce a large number of nutrients, and have strong resistance to rot disease. Therefore, except for the poor management of individual management, weak growth, and poor disease resistance, most of the orchards have no or little rot disease. In the northwest fruit area of ​​China, the apple tree began to produce skin in June, reaching a peak in July. In August, the rot pathogen could be isolated on the skin. At the end of October, the healthy tissue under the stalk was not rotted. It is indicated that during the disease resistance period of apple trees, the rot pathogens mainly parasitize on the dead tissue of the old and old skin, and generally do not extend to the healthy cortex to form rot lesions. During this period, orchards saw that the rot lesions of varying sizes were mostly leftover lesions that were not cured in the spring.
Incidence of
The apple tree is in the dormant period from the deciduous leaves (November) to the spring buds (the end of March or the beginning of April), and it is also the period of apple tree rot. Before the apple tree leaves, a large amount of nutrients flow to the fruit in the tree. After the leaves are removed, photosynthesis, water metabolism and other physiological activities are basically stopped. The contents of nutrients such as sugar and nitrogen are at the lowest level, and the tree is in starvation and disease resistance. Very weak, most prone to rot.
In the spring of February to March (before the exhibition leaves), the temperature is gradually rising in the late stage of the disease, and the temperature of the comprehensive prevention and control measures of the apple aphid is suitable for the growth and reproduction of the rot pathogen, and the rot pathogen on the dead tissue will quickly invade the health. The bark forms new lesions. The original small lesions will expand rapidly, and will become a large lesion after more than 10 days, which is the peak period of rot disease. After the apple tree sprouted and spread leaves, it entered the period of disease resistance, and the rot disease stopped developing.
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