Chlorops oryzae Matsumura, commonly known as the yellow leaf miner, is a species of fly belonging to the family Muscidae. It is also referred to by several other names, such as rice stalk fly, rice fly borer, and double-tailed worm. This pest is widely distributed across various provinces in China, including Heilongjiang, Zhejiang, Jiangxi, Hunan, Hubei, Guangdong, Guangxi, Yunnan, and Guizhou.
The primary host plants of this insect include rice, wheat, millet, bluegrass, and valerian. The damage caused by this pest is mainly due to the larvae, which bore into the stems and feed on the growing points, heart leaves, and young panicles. As a result, oval or elongated holes appear in the center of the plant, which later develop into longitudinal strips. This can lead to broken leaves, distorted or withered new growth, and reduced plant vigor. Infected plants often show symptoms such as stunted growth, delayed heading, smaller and less productive panicles, and an increase in glutinous rice. During the juvenile ear formation stage, malformed white spikes may appear, and some ears may remain incomplete or fail to flower properly. In recent years, the occurrence and impact of this pest have been increasing, making it a growing concern for farmers.
Morphologically, the adult fly measures 2.3–3 mm in length and has a wingspan of 5–6 mm. Its body is yellow when fresh, with the head and thorax being approximately the same width. A large diamond-shaped black spot is present on the back of the head. The compound eyes are large and dark brown, while the antennae consist of three segments: the base is tan-brown, the middle segment is dark brown, and the third segment is black with a rounded tip. The front legs are yellow-brown, with dark black tips. The wings are transparent, with brown veins, and the abdomen is spindle-shaped, featuring dark brown bands on the edges of each segment. Each segment of the first abdominal segment has a single black dot on either side. The underside of the body is pale yellow.
The eggs are white, long-oval, and measure approximately 0.7–1 mm in length. The mature larvae are about 6 mm long, nearly spindle-shaped, pale yellowish-white, and have a shiny cuticle. Their ends are forked. The pupae are 6 mm long, ranging from pale yellow-brown to yellow-brown, with dark spots along their bodies, and also have a bifurcated end.
In terms of life habits, this species typically has 2–3 generations per year in regions like 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. The eggs hatch in mid-April, and the newly hatched larvae move along the leaf backs via dew and enter the plant's heart and leaves, emerging in June. The second generation of larvae hatches in late June and early July, causing damage during the booting and heading stages of rice. Adult emergence is not uniform, and after mating, they migrate to sweet potato fields, autumn vegetables, and early-sown winter wheat, where they lay eggs. One egg is generally laid per leaf.
Environmental conditions play a significant role in the population dynamics of this pest. Warm winters and cool summers favor its development, while temperatures above 35°C can hinder larval growth. High humidity, lack of sunlight, and low temperatures in the field are also problematic. In mountainous areas above 3000 meters, the damage tends to be more severe.
Control methods include avoiding the cultivation of single-season rice in mountainous areas where it may overlap with double-cropping systems, thereby reducing the population. Farmers should focus on managing the second generation of pests and implementing timely control strategies. Monitoring the adult emergence and egg-laying periods is crucial for effective management. When the density reaches 3.5–4.5 adults per square meter or 1–2 adults per 100 tillers, or when there are 0.1 eggs per plant or 2 eggs per bundle, it is time to take action.
To control adult flies, sprays such as 80% dichlorvos EC or 50% dimethoate EC can be applied at a rate of 50 ml per 667 m² in 50 kg of water. For larval control, 40% dimethoate EC can be used at 150–200 ml per 667 m² in 50 kg of water. Alternatively, 50% dimethoate EC can be used at 100 ml per 667 m². For paddy fields with egg masses, root dipping with 40% dimethoate EC for one minute or 50% chlorpyrifos EC diluted 300 times can be effective. The dipping time should be adjusted based on temperature, variety, and plant health to avoid phytotoxicity.
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