It is midsummer, flowers are in full bloom, fruits and vegetables are abundant, and plants enter the peak of growth period. Powderymildew also appeared in the garden, attacking people's beloved flowers and trees. In some cases, the leaves of plants turn gray, in other cases, they shrink and turn black, the buds are burnt, and the fruits and fruits are reduced, which makes the owner very helpless and disappointed. Powdery mildew caused by powdery mildew is a common plant disease in gardens, but it has an unusual way of growth and reproduction, which is very different from other plant pathogens. Most pathogenic bacteria parasitize the internal tissues of plants, secrete hormones, digest and destroy cell walls and membranes, and locally kill leaves or other parts. On the contrary, powdery mildew is an exogenous fungal disease, which only grows on the surface of leaves and forms gray spots without destroying a large number of cells. Instead, it pierces the leaf with its embryo plug, which can attach to the leaf and absorb plant nutrition on the one hand. The ideal breeding environment for powdery mildew spores is moderate temperature, high humidity and slight temperature, which is also the reason why powdery mildew is most rampant in late summer. At this time, the temperature began to drop at night, and the temperature was close to the critical point of condensation in the early morning, so the humidity was particularly high. At the same time, the temperature at night in late summer is mostly between 68 and 80 degrees Fahrenheit, which is the most suitable temperature condition for spore reproduction. At the end of summer, if the sky is cloudy and there is little rain, the humidity will often remain high, and powdery mildew will be particularly serious. In a short time, fungi will cover most of the leaves and absorb water continuously, so that plant cells can not keep full and hinder the growth of leaves. In severe cases, plants will stop growing completely. Because fungi can dehydrate plant tissues, powdery mildew often reduces the drought resistance of plants, which is also the reason why some trees or shrubs susceptible to powdery mildew, such as Cornus officinalis and roses, will wither or even die when it doesn't rain in summer. Although the symptoms of powdery mildew are the same, there are many strains of powdery mildew, and each strain has a specific host. Therefore, the powdery mildew that harms lilacs will not affect Lagerstroemia indica, and the powdery mildew fungi infected by Lagerstroemia indica will not parasitize lilacs, because these two plants are infected with two different powdery mildew strains. Because powdery mildew is a specific pathogen, peony, Chinese rose, four flowers, cucumber, zinnia, zucchini, pumpkin and other plants susceptible to powdery mildew have their specific strains. The best way to control powdery mildew is to choose resistant plant varieties, especially those prone to powdery mildew. Before planting, it is best to find out whether there are varieties resistant to powdery mildew. Taking lilac trees as an example, nine times out of ten leaves will be covered by ash trees in summer, but BetsyRoss, OldGlory, MissKim and Declaration have better resistance. Similarly, when considering planting four flowers, it is advisable to choose two varieties of "Sweet Water Red" and "Cherokee Brave" which are resistant to powdery mildew. Among the rose varieties, "FlowerCarpetseries" is considered to be extremely reliable. Peony in China is the most susceptible to powdery mildew, and it is difficult to find varieties with good resistance. But there is a hybrid between peony and peony, called hybrid peony. Because it was cultivated by Japanese gardener Ito, Americans also call it Ito Parrot. Its resistance to powdery mildew is surprising, and it is a good choice for people who like peony and peony. People who like to grow vegetables will find that melons susceptible to powdery mildew have some disease-resistant varieties, such as cucumber variety Diva, cucumber varieties Success, Sunglo and Sunray, pumpkin variety 18KaratGold and gladiator, which have a good reputation. For those plants that are not resistant to powdery mildew, the key to control powdery mildew is to spray drugs before the disease appears. Because the fungal spores of this disease are all on the surface of leaves, spraying horticultural chemicals can effectively kill them. Fungicides based on potassium bicarbonate or sulfur and copper can also effectively control powdery mildew. These fungicides against powdery mildew can be bought in general gardening centers.

If plants have already shown symptoms of powdery mildew, it is much more difficult to deal with them than to prevent them beforehand. However, the above three pesticides can still be applied, at least to slow down the expansion of the disease and reduce the impact of powdery mildew. In addition to applying pesticides, we should also pay attention to several measures to prevent diseases. First of all, excessive fertilization should be avoided, because fertilizer can promote the softening of stems, which is beneficial to the development of powdery mildew. Secondly, shady places are humid and germs are easy to breed. Don't plant plants susceptible to powdery mildew there. Similarly, plants susceptible to powdery mildew should not be over-watered, and the roots should be thoroughly watered to avoid wetting the stems and leaves. Cleaning the garden thoroughly can prevent or alleviate the problems in the coming year, such as powdery mildew of cucumbers and pumpkins. After the harvest at the end of the season, the melons and vines should be pulled out immediately, and don't wait until the first frost. These infected residual vines and leaves should be bagged and thrown away, not used for composting. Organic control methods of powdery mildew powdery mildew is a worldwide plant disease. Most flowers and trees will be infected with this disease, from poor growth to complete death. It has nothing to do with powdery mildew. However, using milk to prevent powdery mildew is a very effective control method. It is said that scientists have not found the answer so far. It doesn't matter whether there is an answer, but whether there is an effect is the most important thing. When zucchini was planted a few years ago, it was ok in spring and summer. In autumn and winter, the rain gradually increased and powdery mildew began to increase. At the beginning of powdery mildew, seedlings stopped growing and melons could not bear fruit. Because it was close to harvesting seedlings at this time, the zucchini felt a little tired after eating, and I didn't think about pickling, so I just uprooted it. Surprisingly, there has been a lot of rain since this spring. High temperature and high humidity some time ago are the conditions that powdery mildew is easy to occur. I ate a few zucchini in the field before, and the leaves were covered with white spots, which spread quickly. If we don't take any measures, the whole zucchini will be eaten in two days. Zucchini is actually broken this year! Look at the picture: I didn't eat much zucchini this year, but I couldn't bear to pull it out, so I began to think of ways. Backyard planting is not an organic method, and I will never consider it. I know there are two ways to try, one is white wine and the other is milk. There is no other liquor at home except cooking wine, but there is no shortage of milk, so I tried the method of milk emphatically. I found a small watering can and mixed milk and water at the ratio of 1: 10. I break off the seriously ill leaves first, and then spray diluted milk on the plants and leaves as much as possible. Then spray every 3-5 days. After a period of time, it was found that the effect was remarkable. Powdery mildew was not only controlled, but also reduced to a few, and plants began to blossom and bear fruit again. I used this method on early powdery mildew Lycium barbarum trees, and the effect was obvious. It was eradicated only once. A farmer in Shizuoka Prefecture, Japan, based on his years of experience in growing vegetables, summed up a method to prevent and control powdery mildew of vegetables by spraying diluent on diseased plants. First, take a few milliliters of 35-degree liquor and dilute it with water 1 1000 times. Then, pour it into a manual sprayer and spray the diseased plants. The spraying dose shall be subject to the removal of white rust. This control effect is obvious. Once the rust on the diseased plant is washed away, powdery mildew will never happen again. This control measure has been widely used in the production of pumpkin, eggplant, cucumber and other vegetables in his hometown, and achieved quite good results. There are also some crops that are sensitive to chemicals, such as strawberries. Spraying liquid diluent is the most suitable. It is not only a control agent, but also a nutritional protective agent.