The scientific name of this insect is *Nymphula vittalis* (Bremer), which belongs to the family Crambidae, not Acrididae. It is commonly known as Inawashiro, rice straw, or rice leaf roller. This species is widely distributed across China, ranging from the northern regions of Heilongjiang and Inner Mongolia, down to Taiwan, Guangdong, Guangxi, Yunnan, and extending westward to Ningxia, Gansu, Sichuan, and Yunnan.
The primary host plants include rice, as well as other grasses and aquatic vegetation such as water hyacinth and water lettuce.
The larvae are particularly destructive, as they roll leaves into cylindrical tubes, hiding within the water or beneath the surface, and feeding on the leaves. This behavior can severely damage rice crops, reducing yield and affecting plant health.
Morphologically, the adult moth has a body length of approximately 5 mm and a wingspan of about 19 mm. The head and thorax are yellow-white, while the abdomen is light yellow with dark brown scales at the end of each segment. The forewings are yellow with two white stripes running parallel to the outer edge. The outer stripe is narrow, while the inner one is thick and curves toward the wing’s trailing edge. A white stripe runs along the middle chamber, and there is a dark brown spot on the front edge. The middle chamber is small, with two black spots and a diagonal line below it. All white stripes have dark brown edges with white hairs. The hind wings feature dark brown spots at the base, horizontal dark brown lines, and wide yellow lines on the outside. The outer edge is yellow, with black lines inside and outside, and a black line on the outer edge. These lines connect at the front and rear corners. Both wings have gray undersides. The eggs are elongated and lemon-shaped, with a pointed tip, a flat bottom, and longitudinal grooves on the surface. The larvae grow up to 15 mm in length, are flat, and appear light gray. Their heads are light brown with dark brown markings. The first abdominal segment is unusually large, light brown, with an oval ring pattern and long claws on the thorax. The pupa is 8 mm long, pale yellow, with 2–4 spiracles on the abdomen.
This species typically has one generation per year, with adults emerging in July. The larvae construct nests from rice leaves, either resting on the soil at the bottom of paddy fields or floating on the water surface. They feed on roots and leaves, causing significant damage. Transgenic rice varieties may also be affected. After maturing, the stems become weak and prone to lodging. In Ningxia, the population peaks in mid-to-late July, with females laying 30–50 eggs on the water surface.
To manage this pest, several control methods are recommended. First, using black light traps can effectively reduce adult populations. Second, regular field inspections should be conducted, and any detected larvae should be immediately removed. Blocking drainage channels and preventing larvae from spreading is crucial. Spraying 2.5% trichlorfon powder at a rate of 2.0 kg per 667 m² has proven effective in controlling infestations. Additionally, maintaining clean fields and avoiding overwatering can help reduce the likelihood of infestation.
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