What are the control methods for powdery mildew on melons?

I think many people have eaten melon. It is a kind of melon that looks a bit like a pumpkin. It does not belong to vegetables, but should belong to a fruit. There are many people growing melon on the market, because melon is not only tasty but also relatively cheap, so it is deeply loved by the public.

What is melon

Melon, the fruit of a plant in the Cucurbitaceae family, is fleshy, with many locules and many seeds, and is very similar to a berry, but the receptacle and exocarp of these fruits are fused, often forming a thick outer rind, and in classification it is specially called a “pepo”, and melon is a typical example. The fruit of plants in the Cucurbitaceae family is fleshy, with many locules and many seeds, and is very similar to a berry, but the receptacle and exocarp of these fruits are fused, often forming a thick outer rind, and in classification it is specially called a “pepo”, and melon is a typical example.

The fruit of melon is composed of five carpels, and the seeds are attached to the edges of the carpels, belonging to parietal placentation, and the center of each carpel has a false septum derived from the midrib. Most fleshy fruits spread their seeds through animal feeding, while fruits that are not favored by animals must wait until the melon ripens and falls and the rind rots before the seeds have a chance to germinate. The seeds of melon are wrapped in a layer of sweet, nutrient-rich mucilage. Besides luring birds to peck the seeds, this mucilage can also provide the nutrients needed for seed germination.  Symptoms of powdery mildew on melon  Damage is most severe in the late growth stage. It mainly harms leaves. At first, white mildew spots appear on the leaf surface, then gradually spread around, forming nearly round patches. When conditions are suitable, the mildew spots expand very rapidly, and the lesions merge with each other into one area, causing the entire leaf to be covered with a layer of white powdery material. In severe cases, white powdery material can also grow on the melon surface. It mainly harms leaves, and also harms petioles and stems. In the early stage of the disease, small white powdery mildew spots appear on the upper side of the leaves, then spread to the underside of the leaves, and quickly expand to form a white powdery layer. In severe cases, it can spread to the underside of the leaves, stems and petioles. When stems are infected, just as with leaves, small white powdery spots first appear on the stems, and finally the entire stem is covered with white powder. In the late stage of the disease, the entire plant is covered by a white powdery layer, after which the white powdery layer turns grayish white, and scattered or clustered yellowish-brown small granules appear in the white powdery layer, later turning black, namely the cleistothecia of the sexual generation of the pathogen. The diseased leaves become scorched and brittle, causing the fruit to grow slowly in the early stage. After being cured, traces will also remain at the lesion sites. Conditions for the occurrence of powdery mildew on melon  Powdery mildew can occur at 10-25°C. Whether it becomes epidemic depends on humidity and host vigor. It is prone to epidemics when the rainy season begins in summer or when it is dry in early autumn. The functional leaves around the fruit are most susceptible to the disease, and as more fruits set, disease resistance declines. 

Melon powdery mildew is mainly caused by powdery mildew fungi in the phylum Ascomycota and by Sphaerotheca fungi of cucurbits. Both the sexual and asexual forms of the pathogen can overwinter. Its sexual form, the cleistothecia, overwinters with diseased residues left on the ground or on cucurbit crops in greenhouses and plastic tunnels, and the ascospores released the following spring become the source of primary infection; the asexual form overwinters on the host as mycelium or conidia. The mycelium can attach to the leaf surface to infect, while conidia produce germ tubes or haustoria under suitable conditions and invade the leaf epidermis of the host.

Control methods for powdery mildew on melon  After the disease occurs, spray for control with 10% difenoconazole water-dispersible granules at 2000-2500 times dilution, or 40% DuPont Fuxing at 6000 times dilution, or 20% triadimefon emulsion at 2000 times dilution. When using triadimefon, the concentration should be strictly controlled to prevent phytotoxicity. 

1. Agricultural control. 

① Use excellent varieties resistant to powdery mildew. 

② Clean the field: after the melon harvest, thoroughly clean the field. Do not pile diseased residues beside the shed; they should be gathered and burned. During the growing period, weed in time, remove diseased leaves, and take weeds, residues, diseased leaves, etc. outside the field for centralized burning. 

③ Field management: reasonably adjust planting density, prune scientifically to facilitate ventilation and light penetration, strengthen fertilizer and water management and temperature and humidity regulation, and enhance the stress resistance of the plants. Maintain scientific irrigation, apply less nitrogen fertilizer, and apply more phosphorus and potassium fertilizer to prevent excessive vegetative growth and premature aging of the plants. For greenhouse cultivation, pay attention to ventilation and air exchange, control humidity, and lower the temperature. 

2. Biological control. In the early stage of the disease, choose Bacillus subtilis (100 billion per gram) wettable powder at 1000-1500 times dilution, or 3% polyoxin wettable powder at 500-600 times dilution, or 2% Wuyiencin aqueous solution at 300-500 times dilution, or 4% pyrimidine nucleoside antibiotic aqueous solution at 800-1000 times dilution for control, with an application interval of 4-5 days, spraying 2-3 times consecutively. Disease resistance inducers can also be used for control before the disease occurs, such as 0.5% chitosan aqueous solution at 300-500 times dilution, with an application interval of 5-7 days, spraying 2-3 times consecutively.

For friends who grow melon, of course they hope to have a very good harvest every year when planting, but sometimes things often go against one's wishes. When the plants are eroded by diseases, their yield will be greatly reduced. Therefore, in the process of planting, preventing them from being attacked by diseases is very important.