Harm and Control Methods of Leek Root Maggots
Growing leeks is easier to manage than other vegetables, but the leek root maggot is a problem that gives vegetable growers a real headache. Once it occurs, it is difficult to control, has considerable resistance, and is not easy to eradicate. If not controlled in time, it will reduce leek yields. So, what harm do leek root maggots cause? How can they be controlled?
Damage Symptoms
The leek root maggot, or leek maggot for short, is called the delayed-eye mushroom gnat in its adult stage. It causes damage as a larva. The larva burrows into the bulb of the leek, and after being damaged the bulb rots, the aboveground stems and leaves turn yellow and wilt, the plant becomes stunted, and in severe cases the entire plant dies. The leek maggot also damages crops such as scallions and garlic.
Damage Characteristics
Generally in the north, leek maggots pupate to overwinter; in the warmer south, leek maggots still cause damage in winter; in greenhouses, damage is most severe during the winter greenhouse-covering period.
Leek maggot larvae prefer moisture, and soil with a humidity of 20%-24.7% and a temperature of 20°C-25°C is most suitable. Soil that is too wet or dry is unfavorable for the survival and development of each life stage. In summer, high temperature, drought, or high temperature with heavy rain are the leading factors in the decline of leek maggot populations.
Control Methods
1. Reasonable crop rotation. Generally, after growing leeks for 3-4 years, they can be rotated with crops other than scallions and garlic. If paddy-upland rotation can be carried out, the control effect is even better. This not only benefits leek growth but also reduces the occurrence of leek maggots and other pests and diseases.
2. Pest-free transplanting. During seedling raising, soak the seeds to promote germination and early growth, and use pest-free seedbed soil for the seedbed. When transplanting, select bulbs free of maggots.
3. Scientific fertilization. In early spring and after leek harvests, spread plant ash on the bed surface, which can worsen the egg-laying environment for adults and is unfavorable for leek maggot growth. Adult leek maggots like to feed on decaying matter, so applying thoroughly decomposed organic fertilizer can reduce the occurrence of leek maggots. Fertilizer should be applied deeply to reduce egg-laying by seed flies and effectively reduce leek maggot damage.
How to treat leek root maggots? Four green methods are recommended for prevention and control, and pesticide use should target the key period!
4. Chemical control. Target the key period for control. During the peak activity period of adults and the peak egg-laying period of adults, pesticides such as abamectin and lambda-cyhalothrin can be sprayed to control adults and reduce the number of eggs and larvae; when the field plant damage rate is 10% (after diagnosis as leek maggot damage), root drenching can be done with biphenyl + clothianidin, beta-cypermethrin, or neonicotinoid pesticides such as dinotefuran and thiamethoxam.
5. Sticky trapping of adults. During the peak emergence period of adults, sticky insect glue can be used to trap and kill adults, or simple insect sticky traps (yellow boards) can be used directly to trap and kill adults.
6. Sugar-vinegar liquid trapping. Mix sugar, vinegar, liquor, and water in a ratio of 3:3:1:10, and add a 10-fold dilution of 90% trichlorfon crystals to prepare the mixed liquid.
How to treat leek root maggots? Four green methods are recommended for prevention and control, and pesticide use should target the key period!
7. Light trapping. Taking advantage of the phototaxis of adults, during the peak emergence period of adults at night, set up several fluorescent lamps in the leek field and place water basins under the lamps, which can attract adults to fly into the lamps and fall into the water to die.
8. Biological control. Use insect pathogenic nematodes to “control pests with pests”, which can effectively reduce the amount of chemical pesticides used.
In summary of the above control methods, among agricultural measures, applying plant ash is a very good method for controlling leek maggot numbers. In severe cases, use pesticides for control; in milder cases, the latter 4 green methods are recommended for prevention and control, producing healthy green agricultural products.