Rice Downy Mildew
Rice downy mildew, also known as yellowing and withering disease, typically appears in the later stages of the growing season and becomes more noticeable during the peak growth period. Infected plants show yellow and white spots on the leaves, followed by irregular stripes and a mottled mosaic pattern. The inner leaves turn yellow, curl up, and are difficult to pull out. Lower leaves gradually wither, roots become stunted, and the entire plant becomes dwarfed. The leaf sheaths become soft, wrinkled, twisted, and less vigorous. In severe cases, the infected plants fail to produce ears, while mildly affected plants may form small, deformed spikelets that remain enclosed in the leaf sheath or appear distorted and misshapen. The disease tends to worsen in the late stages of the growing season, especially under cool and wet conditions.
The pathogen responsible for this disease is *Sclerophthora macrospora* (Saccardo) Thirumalachar, Shaw & Narasimhan var. *oryzae* Zhang & Liu. It is a type of oomycete, not a true fungus. The spores are spherical, pale yellow-brown, measuring between 65–95 × 4–78 μm. Male gametes are 1–4 in number, lateral, and measure 45–75 × 7.5–10 μm. Oospores start as colorless and develop into yellowish-brown, oval structures measuring 51–75 × 51–75 μm. Sporangia are lemon-shaped, colorless, and occur at the tip of cysts. They grow from stomata, branch out, and contain multiple oval spores with two flagella. After resting, the spores become spherical. This disease can affect over 43 genera of grasses, making it highly contagious.
The transmission of the pathogen occurs primarily through water. The oospores survive in the soil and infect weeds or young rice seedlings. Under flooded conditions, the oospores produce sporangia and zoospores, which then penetrate the rice plants through the stomata. The optimal temperature range for oospore germination is 10–26°C, with the most favorable range being 19–20°C. Disease development is most active between 10–25°C, with the ideal temperature for infection being 15–20°C. The early seedling stage of rice is the most vulnerable period. The disease often spreads through infected seedlings introduced from infested areas. Heavy rainfall, continuous cloud cover, and low temperatures all contribute to the severity of the outbreak.
To manage rice downy mildew, several preventive and control measures can be implemented. First, select high ground for paddy fields and ensure proper drainage by constructing ditches. Second, remove weeds and any diseased seedlings to reduce the risk of infection. Third, apply fungicides during the early stages of the disease. Recommended treatments include spraying 25% metalaxyl WP diluted 800–1000 times, 90% mancozeb WP at 400 times, 80% phosphorothioate WP at 700 times, 64% antiviral wettable powder at 600 times, 58% metalaxyl-manganese zinc or 70% mancozeb-zinc manganese WP at 600 times, and 72.2% propamocarb (Pric) at 800 times. Regular monitoring and timely application of these treatments are essential for effective disease management.
Moisturizing is the foundation of skin care. The basic skin care products that are indispensable for moisturizing and hydrating such as lotions, lotions and essences, how in the end should I choose the real moisturizing products? The easiest way is to look at the active ingredients of the product. Common Cosmetic Ingredients series, common moisturizing ingredients, let's take a look.
1, glycerin, the scientific name of propanetriol, glycerin can be classified as a natural ingredient moisturizer, mild texture, not easy to cause skin allergies, etc.. But glycerin itself is only moisturizing and no skin care function, so it works well for young, healthy skin. If the skin needs multifaceted maintenance, then the maintenance products also need to contain other effective ingredients and glycerin with the use.
2, collagen, collagen on the skin care although important, but its due to the molecular large, directly applied when not accepted by the skin. The real improvement of the skin collagen content is the use of collagen boosters, such as vitamin C, vitamin B3, vitamin A.
3, hydrolyzed collagen, hydrolyzed collagen is the large molecule of collagen to hydrolyze the processing into a small molecular weight of protein. The hydrolyzed protein is not as good as other moisturizers in terms of pure moisturizing effect, but has a certain function of improving skin texture. When you are shopping, make sure that the collagen in the maintenance products is labeled "hydrolyzed collagen", which is the collagen that can be absorbed by the skin. The actual fact is that you can find a lot of people who are not able to get a good deal on this kind of things.
4, amino acids, amino acid moisturizing mechanism and other moisturizers are different, it does not have a strong water absorption, but the skin moisture has a regulatory role, because the moisture content in the stratum corneum is reduced, the amino acid content at the same time reduced, so the maintenance products in the addition of amino acids is necessary to maintain the normalization of keratin function, but amino acids do not belong to the "main moisturizing factor "The main factor is the fact that it is not the main moisturizing factor.
5, natural moisturizing factor, the main components of natural moisturizing factor are amino acids, sodium lactate, urea, etc.. In pure moisturizing effect is not as good as glycerin, but because of its good skin-friendly, can regulate the skin pH function and maintain the normal operation of the keratin, not only has a moisturizing function, but also a certain maintenance function, is also indispensable moisturizing ingredients.
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