Basic pathology of three kinds of diseases and simple pharmacology of corresponding fungicides. Of course, the concepts of pathology and pharmacology I mentioned here are the easiest for vegetable farmers to understand, which may be different from all the current theoretical systems. However, for the majority of vegetable farmers, the concepts of pathology and pharmacology I mentioned are very concise and practical.

1. False bacterial diseases

Mainly cucumber downy mildew, downy mildew is the most important disease of cucumber, also known as dried horse racing, which spreads quickly, is harmful and has great losses. The chemicals used to control cucumber downy mildew are significantly different from those used to control other fungal diseases. Therefore, it is clear in prevention and control to a certain extent, which can reduce false prevention and mistreatment. Although downy mildew is very harmful, there are special and magical chemicals that can effectively control it.

There are too many special chemicals to control cucumber downy mildew. At present, dimethomorph, flumorph, metalaxyl, cymoxanil, silver farfaral, cyazofamid, propamocarb, etc. are common in the market. These chemicals are all special drugs or have a glorious history. Yinfari and cyazofamid are good drugs to control cucumber downy mildew at present. It is no exaggeration to say that their efficacy is magical. Because of the long time of introduction of other chemicals, pathogens have more or less produced some resistance to them, but the control effect is still remarkable.

Because of the existence of these special drugs, other drugs with slightly worse effects, such as mancozeb and chlorothalonil, have been ignored. Recently, new drugs such as Amisi Da and Cuibei have certain curative effects on cucumber downy mildew, or because of the existence of specific drugs such as Yinfari, these new drugs are all eclipsed. Medicaments with special effects on downy mildew are basically ineffective on bacterial diseases and fungal diseases. This is something that everyone should keep in mind.

2. Bacterial diseases

Bacterial diseases that harm cucumber leaves are less harmful to cucumber. In general, it is not necessary to control them specially, but to control other diseases and add a small amount of chemicals to control bacteria can basically solve the problem. However, bacterial diseases such as rotten stems, rotten whiskers, rotten petioles, and necrosis of marrow cavity in cucumber in recent years need to be taken seriously. Most bacterial diseases do not harm cucumber seriously, but up to now, there is no special medicine, such as Yinfali, which has magical effect and can cure downy mildew. The so-called specific drugs for controlling bacterial diseases are only effective in the general sense.

The medicines for controlling bacterial diseases are firstly copper preparations, which are commonly found in the market, such as copper hydroxide, cuprous oxide, copper oxychloride, copper succinate, copper quinoline, etc. It can be said that all blue medicines can control bacterial diseases of cucumber. Copper preparation has a good effect on controlling bacterial diseases of cucumber, but it will cause more or less phytotoxicity to cucumber leaves and form some dry and white ideas. Copper preparation is an ancient medicine, which has certain curative effect on fungal diseases, pseudobacterial diseases and bacterial diseases of cucumber. However, the control effect of copper preparation on various diseases of cucumber is not outstanding. However, one advantage of copper preparation is that all diseases have little resistance to it. At present, no one uses copper to control downy mildew and fungal diseases.

There is also antibiotics, which are typical representatives of agricultural streptomycin and agricultural streptomycin. I used it more than 20 years ago, and I feel that the effect is getting worse and worse, and the disease is too resistant to it, but it is effective for prevention. The common antibiotics in the market are zhongshengmycin. Other agents for preventing and controlling bacteria include chlorothalonil, bromonitrol and so on. I would like to recommend this bromonitrol as a drug to control bacterial diseases. The germicidal mechanism of bromonitrol is completely different from other fungicides for preventing and treating bacterial diseases, and it can effectively kill stubborn bacteria with strong drug resistance.

Generally speaking, the drugs for controlling bacterial diseases are ineffective or have very poor effects on fungal diseases and pseudobacterial diseases. Don't use and don't need to use drugs to control bacterial diseases to control fungi and pseudobacteria.

3. Fungal diseases

The fungal diseases mentioned here are different from those in traditional classification methods. In cucumber production, the fungal diseases mainly refer to ascomycetes or half-known bacteria diseases. In addition to cucumber brown spot, fungal diseases that harm cucumber leaves are just like bacterial diseases that harm cucumber leaves, and the harm to cucumber is far less than downy mildew, such as cucumber powdery mildew, which is very serious When it happens, and has no fatal threat to the growth of cucumber. Before the outbreak of brown spot, people did not treat fungal diseases as the top priority for prevention and control, just like downy mildew

Of course, there are some fungal diseases that are very harmful to cucumber, such as Fusarium wilt, which mainly damages roots. With the popularization of grafting technology, it is no longer a great disease. There is also gray mold that harms young melons. Because of the application of chlorfenapyr, the harm of gray mold to cucumber is greatly reduced. Strictly speaking, there are no special and magical fungicides to control fungal diseases, and the fungicides like Amisi Da are also very effective in controlling fungal diseases of cucumber, but they are far from being described by magic two fungi. It turns out that fungal diseases, especially leaf diseases, are not very harmful, and people don't pay much attention to them. Everyone doesn't care how effective it is after taking medicine. However, since the rampant brown spot disease has become the main disease, it has completely subverted everyone's understanding of fungal diseases that harm cucumber leaves, and it is not surprising that there is a helpless phenomenon.

There are many kinds of fungicides to control fungal diseases, and they are also very complex. The fungicides commonly used on cucumbers can be roughly divided into three categories, but of course this is only my method. My classification principle of fungicides for preventing and treating fungal diseases is that vegetable farmers can understand it clearly, and it is simple and effective in practical application. However, there are many transitional pesticides or special pesticides which are not listed. I can only express regret for the operability of vegetable farmers.

Methyl morpholine manufacturers remind everyone that there are three problems to pay attention to when fighting drugs and preventing diseases:

(1) Traditional fungicides, such as mancozeb, chlorothalonil, carbendazim and thiophanate methyl, have strong resistance to these fungicides, that is, the pesticides mentioned by vegetable farmers are becoming more and more boring. According to the traditional dosage, the effect of controlling cucumber diseases is getting worse and worse. Now spraying this kind of medicine depends on quantity to win. Only by increasing the application amount can the resistance of germs to medicine be offset and the increasingly rampant fungal diseases be dealt with.

(2) Inhibiting drugs, such as myclobutanil, difenoconazole, prochloraz, flusilazole, tebuconazole, all of which are relatively new, have good control effect and are not too resistant to diseases. However, there is a disadvantage that these drugs have different degrees of inhibition on cucumber seedlings. Inhibition is actually a kind of phytotoxicity, and this phytotoxicity is systematic, slow to relieve and difficult to recover; However, traditional fungicides only cause local phytotoxicity to cucumbers and recover very quickly. Proper inhibition is beneficial to cucumber, but if it is added, used continuously, or misused, the effect on cucumber will be terrible. The final result is that the upper leaves become smaller, harder, blackened, the internodes become shorter, the melon strips become shorter, and the melon seedlings look strong but actually grow slowly.

In addition to the above-mentioned several kinds of pesticides, all pesticides with oxazole in common name have inhibitory effect on cucumber. There are exceptions, for example, cyazofamid has no inhibitory effect. But if you don't understand the pharmacology, it's better to be careful.

When using this kind of medicine, we should pay attention to: firstly, it can not be used before cucumber seedling hanging, and secondly, it can not be used when the temperature is relatively low and cucumber seedling grows slowly; Third, cucumber seedlings cannot be used when they are weak. Fourth, it cannot be used continuously or in an increased amount. When the temperature is high and the melon seedlings grow vigorously, the fungicides with inhibition are skillfully used to prevent diseases and control the melon seedlings, thus killing two birds with one stone. Third, the latest drugs: methoxyacrylate fungicides, specifically Amisi Da, Cuibei and Kairun. The characteristics of this kind of medicine are that it is effective against most fungal and pseudobacterial diseases of cucumber, and it has no phytotoxicity, and can promote the growth of cucumber, but the price is too high, and the drug resistance of the disease is produced very quickly after continuous use. With the enhancement of disease resistance and the high price, the control effect of the same price dose on cucumber fungal diseases is not better than that of chlorothalonil. As far as possible, these agents should not be used alone, and should be sprayed with other fungicides.

The above-mentioned three kinds of fungicides have different curative effects on all fungal diseases, but each kind has its own shortcomings. In practical application, according to the characteristics of these fungicides, it is necessary to mix and match them reasonably, so as to control all kinds of fungal diseases safely and effectively. The fungicides against fungal diseases are basically ineffective against bacterial diseases, and some of them have certain curative effects against pseudobacterial diseases, namely downy mildew, but most vegetable farmers will not use these fungicides to control downy mildew, because there are too many specific fungicides to control downy mildew.