The scientific name *Oulema oryzae* (Kuwayama) belongs to the order Coleoptera, commonly known as rice leaf beetles. It is also referred to as back maggots or swine maggots. This pest is primarily found in the northeastern and central-southern rice-growing regions of China.
The host plants include rice, wheat, corn, millet, sorghum, reeds, alkali grass, and other similar crops. These insects are particularly damaging to young seedlings and can cause significant yield loss if left unchecked.
The injury symptoms caused by this pest are distinctive. The larvae feed on the leaf tissue, leaving only the veins or a thin transparent epidermis. This results in white streaks on the leaves, which may eventually turn completely white and dry, leading to withering of the entire plant in severe infestations.
Morphologically, adult beetles measure 3.7–4.6 mm in length and 1.6–2.2 mm in width. Their head, antennae, and small scutellum are black, while the pronotum and legs range from yellow-brown to red-brown. The elytra are blue with a metallic sheen, and the ventral surface is black. The head is engraved, and the antennae extend up to half the body length. The prothoracic plate is longer than it is wide, and the scutellum has an inverted trapezoidal shape. There are 10 longitudinal grooves on the elytra, with nearly parallel sides. The eggs are approximately 0.7 mm long, oval in shape, and initially light yellow, later turning dark green or grayish brown. The larvae grow to about 4–6 mm in length and have four instars. Their heads are small and dark brown, with a pronounced dorsal bulge. Shortly after hatching, they accumulate yellow or dark green fecal matter on their backs. They are about 4.5 mm long and often have a white, cotton-like coating on their bodies.
The life cycle of *Oulema oryzae* involves one generation per year. Overwintering adults emerge in early spring and feed on weeds and grasses before migrating to rice fields when seedlings begin to grow. Eggs are laid near the leaf tips, often in clusters of 2–13 on the leaf sheaths. Newly hatched larvae primarily feed on the heart leaves and then move outward. These larvae avoid light and prefer to feed during morning dew or on sunny days, hiding under the leaves during midday. In the final instar, the larvae spin a white cocoon and pupate inside it. Adults become active in late May and June, and they overwinter after early August. Female adults live for 309–328 days, while males live for 245–277 days. Mating occurs at temperatures between 16–22°C and humidity levels of around 80%. Females mate multiple times, while males do not. The first mating typically occurs between 9 AM and 4 PM, and the second between 6 PM and 11 PM. Spawning begins when the average daily temperature exceeds 15°C.
To control *Oulema oryzae*, several methods can be applied. After the larvae appear, drying the field and adding lime powder can help sweep the larvae off the leaves. Spraying in the early morning, when dew is still present, is effective. Combining this with tillage and mud application enhances control. For larvae in the first and second instar stages, spraying 50% emamectin benzoate at 1000 times dilution, 25% chlorpyrifos EC at 1000 times, 190% trichlorfon 800 times, or 50% phoxim emulsion at 1500 times is recommended. Apply 75 L of solution per 667 m², repeating every 10 days for 1–2 applications depending on the infestation level. Integrated management practices such as crop rotation and maintaining healthy field conditions can also reduce pest populations effectively.
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