The yellow spot disease actually refers to the cucumber target spot disease and belongs to a fungal disease.
I. Fungal pathogenic diseases, Corynebacterium.
Second, the conditions of temperature and humidity. Severe onset of 20~25°C. Therefore, early spring and autumn are severe during delayed cultivation. The winter is not serious. The temperature difference between day and night is particularly serious.
Third, the performance of the symptoms The disease in different growth environments have different symptoms, the general are: yellow and angular spots type. Yellow point type: It can be divided into two forms: rice grains and bean grains. The colors are tan. 1. The rice grain, as its name implies, is a small yellow dot similar to the size of rice grains, mainly concentrated in the upper middle leaves and the new top leaves, similar to bacterial leaf spot of cucumber. The front blade is not obvious on the front, but the observation of light will find the corresponding yellow dots. In the middle and late stages, the leaf surface is obvious, but the spots will not expand, and later the breakage will occur. 2. The bean spot, the spot is slightly larger, the middle color of the spotted spot becomes brown, the surrounding color is still yellow, the spot is overall similar to the target playing brand, and there is a bullseye in the middle. The name of the target spot disease comes from this. (Note the difference with the symptoms of cucumber black spot). Keratotype: mainly occurs in the deep winter cultivation process. The shape is similar to bacterial angular spot. However, no pus marks appear on the back under high humidity conditions. The moldy layer is dark brown and even missing. The spot color is tan.
Fourth, prevention and control measures
1. Develop robust plants and increase plant resistance. The main measures are: the cultivation of robust roots, foliar spray harvest No. 1, potassium dihydrogen phosphate.
2. The main prevention. In the early stage of onset, drugs can be selected: thiophanate-methyl, carbendazim, chlorothalonil, thiram, difenoconazole and other agents. Can also be compounded: difenoconazole + thiram.
3. In the middle and later stages of onset, the dose may be increased, focusing on systemic agents. Usually selected ingredients are: triazoles, prochloraz, pyraclostrobin and so on. For example, myclobutanil, triadimefon, difenoconazole. However, there are no side effects to control the dosage. At the same time, attention should be paid to compounding with protective agents such as: myclobutanil + mancozeb + pyraclostrobin.
Friendship Tip If the vegetable farmers are worried that there is a mixture of bacterial diseases, they can be combined with bacterial agents. However, in order to enhance the control effect of the target spot disease, it is most suitable to select organic copper.
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