The scientific name of this pest is *Nilaparvata lugens* (Stål), belonging to the family Delphacidae, order Hemiptera. It is widely distributed across China, ranging from Jilin in the north to Liaoning, Hebei, Shanxi, Shaanxi, and Ningxia, extending as far west as Gansu, and then southward through Sichuan, Yunnan, and Tibet. The primary host is rice (*Oryza sativa*).
This insect causes significant damage by feeding on the sap of rice plants. Nymphs tend to cluster at the lower parts of rice tillers, while adult females use their ovipositor to pierce the leaf sheaths and leaves, causing dehydration or infection with sclerotia. Their excreta often lead to mold growth, which interferes with photosynthesis and respiration, ultimately causing severe wilting or even death of the rice plants. Commonly known as "erupting," "toppling," or "collapsing," it can lead to complete crop failure in extreme cases.
The life cycle of *N. lugens* varies depending on the region. In Hainan, there are 12–13 generations per year, with overlapping generations and no overwintering. In Guangdong, Guangxi, and southern Fujian, 8–9 generations occur between March and May. In southern Guizhou, 6–7 generations occur from April to June, while in the middle and lower reaches of the Min River, Guizhou, northern Fujian, and southern Zhejiang, 5–6 generations occur from May to June. In northern Jiangxi, Hubei, Hunan, Zhejiang, southeastern Sichuan, Jiangsu, and Anhui, 4–5 generations take place from mid-July to mid-August. In northern Jiangsu, northern Anhui, and southern Shandong, only 2–3 generations occur between July and August. In other northern rice regions, there are 1–2 generations, also occurring between July and August.
The main population sources migrate from south to north, following warm and humid weather patterns during the summer. There are about five large-scale migrations each year, with a return migration in the fall. The egg development period varies with temperature: 17 days at 17°C, 9 days at 23–24°C, and 7–8 days at 27–30°C. Nymphs develop in 15–16 days at 24–26°C. Short-winged adults remain in one place, while long-winged adults are migratory. They can fly strongly shortly after emerging and travel via high-altitude air currents. During spring and summer migrations, they fly at altitudes of 1500–2000 meters, where high humidity aids their movement. The initial flight temperature is around 18.2°C. Adults show strong attraction to green rice, and males can mate multiple times. At 24–27°C, mating begins 2–3 days after emergence, with females laying an average of 200–700 eggs. Each generation has a lifespan of 10–18 days, with 10–40 reproductive cycles per generation.
Nymphs and adults prefer moist and humid environments, typically inhabiting rice plants within 10 cm of the water surface. When infestation levels exceed 0.4 per cluster, uneven distribution occurs, leading to field collapse. At later stages of rice growth, many long-winged adults emerge and migrate out. The 1–3 age stages are critical for wing-type differentiation. Recent changes in farming systems, such as complex rice varieties and longer maturation periods, have contributed to increased populations and more severe damage.
The optimal temperature for the growth and development of *N. lugens* is 20–30°C, with 26°C being ideal. High temperatures in late autumn promote its occurrence. Rainfall during migration seasons increases the likelihood of landing and large-scale outbreaks. Wet fields, excessive nitrogen fertilizer application, dark green seedlings, high density, and prolonged deep irrigation all favor its reproduction and cause heavy damage. Natural enemies include the rice blast wasp, *Trichogramma* species, rice red beetle, nematodes, and black-shouldered plague.
For prevention and control, early forecasting and analysis of migration trends are essential. Crop planning should be uniform, with rational planting arrangements to reduce insect sources. Field management should focus on balanced fertilization and water control to prevent excessive growth and reduce humidity. Resistant rice varieties, such as Xiaoyou 6, Xiang Zao No. 1, Guang You Qing, Qi Gui Zao 25, Wei You 35, II You 46, D You 64, Nanjing 14, Yang Dao No. 3, Shuiyuan 290, Xiushui 620, and others, should be promoted to prevent new biotypes. Protecting and using natural enemies is also important.
During the nymph hatching peak and 2nd–3rd instar stages, applications of 2.5% fluquinconazole wettable powder (20–30 g/667 m²) in early and late rice fields, or 50 g in late rice fields, can be effective. Alternatively, 10% suspension agents (50–100 ml/667 m²) or 10% imidacloprid WP (2000 times dilution) at 10–20 g/667 m² with 60 kg of water can be used. These treatments provide over 90% control for 30 days. Other options include 80% insecticidal powder (35–40 g/667 m²), 20% Confodol Concentrate (6–8 ml/667 m²), 40% inactivated bellflower oil (30–40 g/667 m²), and 10% Dagongchen WP (2 g active ingredient/667 m²). These products also help control other pests like leafhoppers and leaf rollers.
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Melanin is a protein that exists in the basal layer of everyone` s skin. The exposure to ultraviolet radiation can cause changes in melanin, generating a substance that protects the skin. Then, melanin moves through the layers of cellular metabolism and reaches the epidermis of the skin, resulting in skin problems such as pigmentation and uneven skin color.
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By softening the stratum corneum, these substances accelerate the shedding of dead cells in the stratum corneum and promote the metabolism of the epidermis, so that the melanosomes entering the epidermis fall off with the rapid renewal of the epidermis during metabolism process, thereby reducing its impact on skin color.
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