Chlorops oryzae Matsumura, commonly known as the yellow leaf miner or rice stalk fly, is a pest belonging to the Diptera order. It is also referred to as the rice fly borer or double-tailed worm. This insect is widely distributed across several provinces in China, including Heilongjiang, Zhejiang, Jiangxi, Hunan, Hubei, Guangdong, Guangxi, Yunnan, and Guizhou.
The primary host plants of Chlorops oryzae include rice, wheat, millet, bluegrass, and valerian. The larvae are particularly damaging, as they bore into the stems, attacking the heart, growing points, and young ears of the plant. This results in oval or elongated holes that gradually develop into longitudinal strips, causing leaves to break, new leaves to become distorted or wither, and overall plant stunting. Affected plants often show increased numbers of tillers, delayed heading, smaller panicles, and higher levels of glutinous rice. During the juvenile ear formation stage, distorted white spikes may appear, and some ears might be incomplete or fail to flower properly. In recent years, the damage caused by this pest has been increasing, making it a growing concern for farmers.
Morphologically, the adult insect measures 2.3–3 mm in length, with a wingspan of 5–6 mm. Its body is yellow, and the head and thorax have similar widths. A large black diamond-shaped spot is present on the back of the head. The compound eyes are large and dark brown, while the antennae consist of three segments—tan-brown at the base, dark brown in the middle, and black with a rounded tip. The wings are transparent, with brown veins, and the legs are yellow-brown, ending in dark black tips. The eggs are white, long-oval, and measure 0.7–1 mm in length. The mature larvae are about 6 mm long, spindle-shaped, pale yellowish-white, and have a shiny skin. Their ends are bifurcated. The pupae are 6 mm long, pale yellow-brown to yellow-brown, with dark spots and a bifurcated end.
In terms of life habits, Chlorops oryzae typically has 2–3 generations per year in regions such as Fujian, Hunan, Hubei, Guizhou, Yunnan, and Zhejiang. In Xinning County, Hunan, adults emerge at the end of March and early April, laying eggs on seedlings, which hatch in mid-April. The newly hatched larvae move along the leaf backs via dew and enter the heart and leaves, emerging in June. The second generation of larvae hatches in late June to early July, causing damage during the booting and heading stages of rice. Adult emergence is not uniform, and after emerging, they move to sweet potato fields, then to potatoes, autumn vegetables, and early-sown winter wheat leaves to lay eggs. One egg is usually laid per leaf. The insect thrives in warm winters and cool summers, but high temperatures above 35°C can hinder larval development. Dew, lack of sunlight, humidity, and low field temperatures are significant factors affecting its population. In mountainous areas above 3000 meters, the damage tends to be more severe.
For control, it's recommended to avoid planting single-season rice in mixed-crop areas with double-season rice, as this can help suppress the population. Farmers should adopt a strategy that focuses on controlling the second generation and managing the timing of pesticide applications effectively. The periods when adults emerge and eggs hatch are ideal for intervention. When there are 3.5–4.5 insects per square meter in the field or 1–2 insects per 100 clusters, or when the average number of eggs per plant reaches 0.1, it's time to take action. Spraying 80% dichlorvos EC or 50% killer pine EC at 50 ml per 667 m² with 50 kg of water is effective for controlling adults. For larvae, 40% dimethoate EC (150–200 ml per 667 m²) mixed with 50 kg of water can be used, or 50% killer pine loquat EC at 100 ml per 667 m². Alternatively, 3% carbofuran granules can be applied at 2–3 kg per 7 m², mixed with 20 kg of fine soil. For fields with egg masses, dipping the roots in 40% dimethoate EC for one minute or using 50% locust chinensis EC diluted 300 times, or 36% locust chrysanthemum EC, is recommended. Dipping time should be adjusted based on temperature, seedling variety, and quality to avoid phytotoxicity.
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