the key to control apple tree disease is to use medicine skillfully, that is, to use medicine in the key period of disease control. in order to achieve this, we must understand the occurrence law of the main diseases in production, and then according to the occurrence law, in the most sensitive period of the disease, use drugs in advance to control the bacteria in the non germination or non infection state, so as to achieve twice the result with half the effort.
1、 brown spot
in the following spring, when there is a lot of rain from april to may, a large number of conidia will be produced (dry and retting diseased leaves have no ability to produce conidia), and they will infect the leaves close to the ground through the rain splash. they will start to suffer from high temperature and humidity in may to june, and a large number of diseases will occur in july to august. when the temperature drops in october, the damage will stop. the incubation period is 13 to 55 days.
2、 leaf spot
the hyphae lived through the winter in the affected leaves, branches and bud scales, and produced conidia in the spring of the second year, which spread with the air flow and wind and rain. the hyphae began to infect 7-10 days after anthesis, and a large number of high temperature cases occurred in may june and august. the spores of the infected leaves were formed in late april to early may, and on the branches in july.
3、 chakra disease
it is also called rough skin disease and brown rot disease. it mainly damages branches and fruits. the mycelium of the fungus lived through the winter in the diseased tumors of the branches and trunk. in march to april of the next year, the fungus first infected the branches and then the fruits. from june to july, it infects young fruit, but does not occur. when the fruit is under high temperature and drought in the near mature stage, the disease is more serious. the peak of the disease occurred before harvest and 1 month after storage. the center of the disease is lenticel, which forms oblate reddish brown spots, the center protuberance is tumor like, the edge of the disease is cracked, and black small particles are produced in the middle of the second year. the center of the fruit disease is the lenticel, which produces the light brown dots (red dots) in the form of water stains. after the enlargement, the concentric rings of light and dark brown are formed, and there is the overflow of the tea brown mucus. the whole fruit rots quickly and gives off the sour odor. in the early stage of growth, rainfall often occurs early, while in the mature stage, high temperature and drought are more serious, and vice versa.
mainly harmful to fruit. in the second year, the conidia spread through rain and insects, and invaded the fruit through lenticels, and infected many times. generally, from late may to early june, it enters the peak period of infection. from july to august, high temperature and high humidity is the peak period of disease onset, and a large number of diseased fruits appear. after the disease, the fruit was initially brown round spots, then dark brown (or black) spots and sunken, and the black small dots of the central protuberance were arranged in concentric rings. high temperature, high humidity and heavy rain. the orchard is closed and low-lying, with poor ventilation and light transmission.
in a word, there are three key periods for disease prevention: one is to clear the garden in winter and spring, to destroy the overwintering places and reduce the overwintering base. the second is to strengthen the drug protection from 3 to 5 days after anthesis to before bagging to prevent the infection of pathogens. third, pay attention to climate change, spray before rain to prevent the spread of pathogens.