Chives are also known as root maggots and maggots, and their adult insects are called red-eyed grass mosquitoes or yellow-footed qin mosquitoes. Maggots that harm leeks are mainly the larvae of the late-eyed grass mosquito. The late-eyed Asteraceae is a genus of diptera in the family Diptera, which occurs throughout the country.
The hosts of leeks include leeks, green onions, garlic, flowers and Chinese herbs, etc., and green onions, leeks and garlic are more seriously affected. The larvae cluster on the leaf sheath and bulb in the underground part of the leek to eat the damage, the leek is generally affected by the symptoms from the outer leaf, the initial outer leaf side appears strip yellow, followed by the whole leaf, the whole plant withered yellow, until the leek dies continuously. Leek maggots can be harmful multiple times a year. First, in the rain to the Qingming hazard is called "spring maggots", at this time the soil begins to thaw, the main harm is the germination of leek sprouts, often so that leeks can not germinate in spring, resulting in lack of seedlings and ridges, the harm is serious up to more than 70%.
The second is to harm the leaf sheath before and after the summer, which is the yellow ripening period of wheat, so it is called "wheat maggot", which often leads to rhizome rot, leek leaves yellowing, wilting and drooping, until the whole plant dies of yellowing. The third occurs between the high temperature and rainy summer in the middle of summer, the summer heat, also known as "maggots", when the summer temperature is high, the larvae move downwards, mainly harming the bulbs, making the entire bulb rot, causing a large number of plants to die in serious cases. Fourth, when the dew is endangered at the autumn equinox, it becomes an "autumn maggot", once the leek is endangered by the leek maggot, the leek plant withers and cannot germinate new shoots, although some can germinate new shoots, but due to excessive damage, the seedlings that grow are weak and weak, and it takes 1 to 2 years of fertilization to restore normal growth. In general, in terms of the degree of harm, it is still the spring maggot and the maggot that are the most serious.
Adult: Small, 4-6 mm long, black-brown all over the body. The antennae are filamentous in 16 segments, with micro-hairs, and the compound eye is connected to the antennae in a thin "eye bridge", with 3 single eyes. The back of the thorax is raised, and the tibia of the foot is not ended with spines. The leading and subfortrend veins of the forewings are thicker. The feet are slender brown. The abdomen is cylindrically elongated, tapering towards the end, 8 to 9 segments, and the abdominal length is 2.0 to 4.5 mm. The male mosquito has a terminal abdomen - a pair of iron grippers.
Eggs: oblong,opalescent, milky white, 0.17 to 0.24 mm, mesh-like, often in the surface of the leek bush around the rhizosphere of 3 to 5 emanating seams. Larvae: slender, white linear maggots, body length of about 0.4 cm, no feet, full body milky white, mouth organs are very small, translucent, the head is black and shiny, belonging to the full head. Pupae: the pupa is a naked pupa, oblong oval, the pupae is initially yellowish-white, later transformed into yellow-brown, gray-black or reddish-brown before feathering; the head is copper-yellow, shiny, burrow-like and multi-grained in the affected leek plant or nearby soil.
Leek maggots often congregate in a clump of leek roots, up to 500 to 600. It overwinters in the form of old mature larvae or pupae in soils 3 to 4 cm deep in the rhizome and rhizosphere of leeks. Adults are active during the day and in the morning, and their activities are weakened at noon and on cloudy days, and they can be migrated over short distances. The general egg stage is about 7 days, the larval stage is 10 to 15 days, and the pupal stage is about 7 days. 2 to 6 generations occur in a year, and the number of generations increases with the southward movement of the region, and 4-5 generations occur in the Central Plains. In general, open leeks sprout and are endangered by overwintering larvae in the early stages of growth. Early to mid-March is the peak of the first generation of adult insect feathering, mid-to-late April is the peak of the first generation of larval harm, early to mid-October is the peak of the third generation of larval harm, after the frost fall the fourth generation of larvae into the soil to overwinter, but in the greenhouse, greenhouse, yangqi winter can still continue to endanger. Among them, the first and fourth generations are seriously harmful.
The hatching larvae often burrow through the epidermis of the sheath of the leek leaf, moth the internal tissue, and gradually feed upward from the base. Once the growth point of the leek is damaged, the plant will wilt and die, and even cause decay. The harm of leek maggots is related to the age of leeks, and the seedlings in the year of sowing have small roots, strong air permeability around the plant, and the degree of harm is light. Plants that are more than two years old have vigorous growth potential, a large number of leaves, an increase in tillers, and poor ventilation near the ground, which is more harmful.
The occurrence of leek maggots is related to climatic conditions, and the hazards are heavy when the average daily temperature is about 17 °C, the relative humidity is less than 50%, and the amount of precipitation is below 30 mm. When there is a lack of oxygen between the water and soil gaps in the ground area after the rainstorm, the harm is also lighter. Leek maggots have flavor and phototropism. Its occurrence is mostly related to the special smell contained in the ground at that time, adult insects have a certain tendency to odor, sweetness, sourness and wine taste, especially with strong odor, if the application of uncorried organic fertilizer, strong odor can attract adult insects to lay eggs, the harm is quite serious. Even odors occur during the blooming period of leeks, or odors occur when the roots rot, which will attract a large number of adult worms to lay eggs, resulting in a serious occurrence of leek maggots. At the same time, leek maggots have a certain tendency towards blue light and yellow light.
(1) Scientific fertilization: to apply fully decomposed organic fertilizer, do not pour uncorried human feces and urine during the peak period of adult insect occurrence, and fertilize to achieve trenching and deep soil application.
(2) Irrigation control: In the early spring or autumn when the larvae occur, continuous irrigation 2 to 3 times, each morning and evening irrigation once a day, irrigation to submerge the ridge back as the standard, so that the root maggot suffocation death, can reduce the harm.
(3) Leek removal method: use bamboo skewers to remove the soil around the leek root to dry, resulting in a dry environment, which can reduce the hatching rate of larvae and the feathering rate of adult insects, and reduce the harm. The time for removing leeks is advisable if the spring ground topsoil is not completely thawed, preferably sooner rather than later.
(4) Watering ammonia: Ammonia is a liquid nitrogen chemical fertilizer, used to water leeks, in addition to better fertilizer efficiency, there is also a good role in controlling leek maggots. 2 to 3 days after the first stubble of leeks is harvested, the roots are evenly irrigated with 3% ammonia, which can effectively reduce the harm of leek maggots.
(5) Sweet and sour liquid to trap adult insects: with sugar: vinegar: wine: water according to the ratio of 3: 3: 1: 10 add 1/10 of the crystal enemy insects into a mixture of liquid, packed in porcelain containers, 10 per acre evenly placed, can effectively trap adult insects, 5-7 days to replace once, add vinegar solution once every other day.
(6) Pharmaceutical control: in the early to mid-March, early to mid-June, mid-to-late July, August to mid-October adult feathering peak, with 10% Juma emulsion 3 000 times liquid or 2.5% cypermethrin emulsion 3000 times liquid spray, can kill adult insects, 9 to 10 am the best effect. During the peak period of larval harm (mid-April, mid-to-late July, mid-to-late October, late December to late January), use 20% Juma emulsion 2000 times liquid or 50% octylthion emulsion 1000 times liquid to prevent root control, 7 to 8 days, 2 to 3 times in a row. If it is a protected leek cultivation, the leek root should be opened before the buckle film, dried for 7 days, can freeze and kill some overwintering larvae, and then irrigate once, the effect is better.
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