Pear black spot, commonly known as "splitting the fruit," is the main disease of certain pear varieties in Japan (such as the 20th century, Hakata Green, etc.), and is particularly serious in the rainy areas.This disease mainly damages the fruits and causes a large number of cracking and rot. It can also invade the leaves and shoots, causing early defoliation and declining tree vigor.
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Symptoms: The earliest onset of tender leaves. The needles begin with a large, round black spot. Afterwards, the lesion gradually enlarges in a circular or irregular shape. The center is grayish-white, with dark brown edges and a pale yellow halo. When the disease is severe, the lesions on the leaves are contiguous, and the leaves are shrinking and deformed.
Young fruit victims, initially produced in the fruit surface black round needle large spots, and then gradually expanded, the lesion was slightly depressed, there are fine ring lines, to the fruit expansion period, the site cracks, cracks Deep and wide, easy to cause early fruit drop. The fruits of growth are similar to those of young fruit when damaged, but the rapid expansion, large lesions, and cracking are more serious. It is easy to cause insects to smoke and cause the whole fruit to become black. Corruption falls off.
The lesions on the new shoots were black in the early stage, oval in shape, slightly sunken, and later light brown in colour, with small cracks on the edges. After the pear buds are victimized, they become black and die.
?? Characteristics of the disease germs with mycelium and conidia in diseased branches, diseased fruit and disease buds, diseased leaves overwintering. In Shanghai, a small amount of spores usually formed in early April, began to invade the leaves, and spores began to increase significantly at the end of April and beginning of May, and began to invade young fruit. The peak of spore flying in the middle and late May was also the peak of the year. Until the end of June, more spores were still produced. Spore production can continue until the end of October. From September to October in Shanghai, the climate is warm and rainy. Therefore, there is also a peak of incidence in autumn shoots from September to October, and it becomes an important pathogen in the next year. The development of pear black spot disease is closely related to temperature and rainfall. The optimum temperature for conidial germination was 25-27°C, and the germination was poor when the temperature was above 30°C or below 20°C. The conidia formation, germination, and invasiveness require rain in addition to temperature conditions. When the general temperature is 24-28°C and continuous rain, it is most conducive to the occurrence and spread of the disease; when the temperature is high, it stops expanding.
The strength of the tree vigor has a certain relationship with the onset. Strong tree vigor, less dead shoots, weaker onset, lighter onset; debilitating tree vigor, or partial application of nitrogen fertilizer, organ tissue is not filled, the incidence is often severe. Low-lying, poor drainage is good for hair growth?
There was a significant difference in the degree of disease among the breeds. In Jiangsu, Zhejiang, and Shanghai, the most severe disease occurred in the 20th century in Japanese pears, followed by Hakata Green and the moon. Yanzhou Sydney can also feel slightly Bo?
The control method???
1 Increase organic fertilizers and keep fruit reasonably to promote robust trees and drainage work, reduce the humidity in orchards, and create environmental conditions that are not conducive to disease.
??2 Carefully remove fallen leaves, fruit drop, diseased shoots, and diseased shoots; take care to cut off branch shoots that cannot germinate when the pear tree germinates. After the clearing of the garden, the deep-falling soil and deep-buried sick bodies will eliminate various sources of overwintering.
For the 20th century, it is advisable to use pruning to cut short the truncated cultivars in the 20th century. This is especially true for trees that have entered a lot of results; young trees should be retracted after the tree’s potential is reduced to avoid continuous growth. Long-term release to prevent tree decline and pathogen accumulation.
4 pharmaceutical control. During the dormant period, a mixture of 0.5% sodium pentachlorophenol and Baume 5 degree lime sulfur can be sprayed. During the growth period from mid-April to mid-June, attention should be paid to spray protection. Especially late April to mid-May is the period when young fruit is most likely to get sick. It must be done immediately after the rain. Shorter interval or use of spreading agent to prolong the efficacy. In heavy orchards, spraying protection is also required during the fall season. The use of 100-150 mg/L of "wind-enriching bacteria" has a significant effect on the control of pear black spot; 50% of acetaminophen WP 1500 times, and 10% of POD 1000-1500 times.
?? 5 early bagging, protect the fruit. It usually starts at the beginning of May and is completely covered before the rainy season. When bagging, pay attention to "pick up the net and get good nets." And pay attention. First spraying, after bagging, so that young fruit "with medicine into the bag" to improve the control effect of bagging, so that "spring rain medicine to deal with, Meiyu bag protection."
