Paddy rice weevil

The scientific name *Echinocnemus squameus* (Billherg) belongs to the order Coleoptera. It is commonly known as the rice elephant beetle. This pest is widely distributed across various rice-growing regions in the country. The host plants of this insect include rice, cotton, melons, sweet potatoes, tomatoes, wheat, and corn. The larvae primarily feed on rice roots underground, causing the rice plants to turn yellow and eventually wither when infestation is severe. Adult beetles feed on young rice seedlings near the water surface, creating a row of horizontal holes in the plant's stem. These injuries can lead to broken stems that float on the water. Morphologically, adult beetles are about 5 mm long, with a gray-black body covered in dense grayish-yellow scales. The head extends into a slightly curved tube-like structure, and the mouthparts are located at the tip of this structure. Their antennae end with slight swelling and are dark brown. The wings have 10 longitudinal grooves, with the inner three being slightly darker. A rectangular white spot is present towards the rear. The eggs are oval, measuring 0.6–0.9 mm in length, translucent, and initially white before turning dark yellow. The last-instar larvae are approximately 9 mm long, with a brown head, milky-white bodies, and many wrinkles. They curl toward the ventral side and lack legs. The pupae are about 5 mm long, with fine wrinkles on the ventral surface, and have one pair of stings at the distal end—white at the base and gray at the tip. In terms of life habits, the rice elephant beetle has one or two generations per year depending on the region. In Zhejiang, it has one generation, while in Jiangxi and Guizhou, it typically has one or two generations. In Guangdong, it usually has two generations. Adults overwinter in the first generation area, and the first and second generations often overlap. Both adults and larvae can survive the winter, with some individuals overwintering alone. Larvae and adults often overwinter in the rhizosphere, about 3–6 cm deep in the soil. Adults may also overwinter in fields and weeds. In southern Jiangsu, overwintering adults lay eggs from May to June in the following year, emerging in October. In Jiangxi, adults lay eggs in mid-May to early June, and larvae hatch in late May. The first generation emerges in mid-July to August, while the second generation hatches in late July to early August. Some larvae may overwinter after feeding or eclosion in October. The pest is most active during the early rice tillering period. One generation takes about 2 months, while the second generation can last up to 8 months. Egg development lasts 5–6 days, larval development 60–70 days, and overwintering larvae up to 6–7 months. During the flood season, adults become active in the morning and evening, hiding in grasses or between rice stalks during the day. They exhibit pseudo-dead behavior and phototaxis. Before laying eggs, they create small holes about 3 cm from the rice stem or leaf sheath, laying 13–20 eggs per hole. Larvae prefer to feed on young rice roots in the soil, typically within 3–7 cm depth. Sandy paddy fields, dry fields, and areas with poor water retention are more vulnerable. Warm and rainy spring conditions favor both larval development and adult emergence. Early spring rice during the tillering stage is ideal for adult egg-laying. For prevention, agricultural control measures include removing weeds around field edges and ditches. In spring, plowing the fields deeply helps bring adults and larvae to the surface, where they can be buried or burned. In areas with severe infestations, applying 50% pine oleoresin oil diluted 800 times, 90% trichlorfon crystals diluted 600 times, or 40% methyl isothiophosphate emulsifiable concentrate at 100 ml per 667 m² can be effective when rice leaves are damaged. Alternatively, 40% methyl isothiophosphate cream can be scattered at 175 ml per 667 m², achieving a 96% control rate after 10 days. Additionally, 3% dandan granules can be applied at 3 kg per 667 m², combined with draining the field and sprinkling lime or tea cake powder (40–50 kg per 667 m²). These methods help reduce pest populations effectively.

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