New countermeasures for prevention and control of apple mold disease
The symptoms of mildew, rot, and other symptoms of the apple's ventricle during the late growth and harvest period of apples are generally referred to as "mushroom heart disease" in China and commonly referred to as "mushroom heart and heart rot."
"Mushroom heart disease" occurs widely and occurs almost everywhere in the apple producing regions of the world. In China, the disease occurred in Shaanxi, Shandong, Henan, Shanxi, Liaoning, Sichuan, Gansu and Hebei provinces. According to a large number of investigations in Luochuan and Baishui in Shaanxi Province in recent years, the disease rate was 7.9%-36.6% and the average disease rate was 20.1%.
For mycotic disease, a large number of pharmaceutical prevention and treatment studies have been conducted overseas. Studies have shown that bactericides such as benzoate, captan, doconin, iprodione, mancozeb, etc. are not effective, and other pesticides such as polyoxin, The methoxy acrylates and triterpene esters have certain control effects, but the control effect is not stable. There are significant differences between the orchards during the year.
In order to clarify the reasons for the poor control of the disease, we studied the pathogenic components of the fungal pathogenesis, the infection period of the pathogen, and the effects of the agents on different pathogens, and obtained some new findings.
The author divides the symptoms of apple fungal heart disease into three types: browning type, moldy heart type and heart rot type. Browning type and moldy heart type are caused by various Alternaria alternata and Cladosporium spp.; Heart rot type can be caused by pink sporangiospores, epidichospores, Fusarium, Penicillium and Stenoflagellium. Moldy heart type and heart rot type often occur mixedly.
The pathogenic bacteria were isolated at different stages of fruit and flower development of Red Fuji apple and it was found that there were significant differences in the infection period of different pathogens. For example, Alternaria spp. has a separation rate of 90% in newly formed flower buds (in November of last year), and has been maintained in the flower bud opening stage, inflorescence extension stage, inflorescence separation stage, bloom stage, flowering stage, and final flowering stage. With a separation rate of about 60%, the isolation rate in the young fruit period is between 13% and 40%; and the dendrosyclospora can be separated (3.3%) at the end of the host's dormancy (2-3 months) before the final flowering period. The segregation ratio increased to a certain extent (33.3%), and the segregation ratio in young fruit after 20 days of the final flowering period increased significantly, reaching 80%; the pink-sporing fungus was isolated in young fruit from June (40 days after the final flowering period). The separation rate was 3.3%. After one month (70 days after the final flowering period), the separation rate was greatly increased to 43.3%.
These results indicate that the pathogen of the apple fungal heart disease can invade fruit from the pod borehole, and can also directly infect the fruit through flower buds and flowers.
For the three fungicides commonly used in the production of apple mold, polyoxins, NPK 120 and thimycepin, the inhibitory activity of 8 dominant pathogens of mycoticosis was determined and 3% of polymyxins were tested. The five kinds of pathogenic bacteria (Alternaria sp., Alternaria dendrilamii, Alternaria alternata, Cladosporium sp. and Pinkiasporium spp.) had a good inhibitory effect and the inhibition rate reached above 90%. The three pathogens tested (Inhibitory effects of C. purpurea, Fusarium sp 1.5% thiflubene inhibited 4 kinds of pathogens (Alternaria sp., Alternaria dendrilamii, Cladosporium sp. and Pinkiasporium spp.), and the inhibition rates were all above 90%, while the four kinds of pathogens (fine The inhibitory effects of Alternaria alternata, Clostridium perfringens, Fusarium sp 4% NR 120 exhibited only a high inhibitory activity against P. microsporum (inhibition rate of 94.2%), and the effect against other fungi was generally or poorly exhibited. It shows that the pesticides commonly used in production such as polyoxin, thimethoxone, and Nongkang 120 have a good effect on some pathogens of apple mold disease, but have poor or no effect on the rest of the pathogens. This result partly explained the reason for the poor control of apple mold disease in production.
To this end, the following issues must be taken into consideration in the prevention and treatment of apple mold disease: First, apple mold disease is caused by a mixture of various pathogens, and must be targeted against multiple pathogens in the prevention and control; second, the use of broad-spectrum agents should be used if pesticides are used. Can not cover a variety of pathogens, you need to use a mixture of several agents; Third, the period of pathogen infection continued for a long time, from the previous year, flower buds began to infect, for the opening of the crop, the fruit development of the entire growth period there is invasive Because of the potential threats, it is necessary to consider increasing the number of pesticides to be applied and choosing the best period for prevention or control, or using biological agents with sustainable effects to prevent and control.
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