New strategy for green prevention and control of leek maggot

The leek maggot, commonly known as the leek worm, is the most severe pest in the growth process of leeks. Its larvae gather at the roots of leeks, feeding on the pseudostem and bulb, causing damage. If preventive and control measures are not taken in a timely manner, it will usually lead to severe yield reduction or even total crop failure. Currently, the prevention and control of leek maggots mainly rely on chemical insecticides applied through root irrigation. However, general chemical pesticides often fail to achieve ideal control effects, and there are often instances of excessive pesticide residues, which also damages the ecology of vegetable fields. Especially in recent years, with the banning and restriction of some highly toxic and highly persistent pesticides, the prevention and control of leek maggots face the situation of limited available pesticides, high control costs, and poor control effects. The "solarization and high-temperature mulching method" and the "biological control method using entomopathogenic nematodes" are new technologies for the prevention and control of leek maggots, invented based on systematic research on the bioecological characteristics and field occurrence patterns of leek maggots.

The "solarization and mulching method" is a green and environmentally friendly advanced physical control technology with a long effective period. The "biological control method using entomopathogenic nematodes" utilizes the specific parasitism of entomopathogenic nematodes to achieve biological control. These two technologies are innovative and new products that adapt to the zero growth of pesticide use and green control technology, providing technical support and guarantee for the quality and safety of leeks. Currently, the municipal plant protection system has made arrangements for the demonstration and application of the above two new technologies to ensure the effectiveness of the new technology for controlling leek maggot.

Attachment 1:

Key points of prevention and control technology for "solarization and high-temperature mulching method"

This technology does not require any chemical pesticides, is easy to operate, achieves thorough prevention and control, is cost-effective, labor-saving, time-saving, environmentally friendly, and has a long effective period. It is an advanced physical prevention and control technology for leek maggot.

1. Prevention and control mechanism

The "solarization and mulching" technique is designed to exploit the characteristic of the leek maggot's intolerance to high temperatures. It involves laying a transparent, heat-retaining, and drip-proof film on the ground, allowing direct sunlight to penetrate the film and elevate the soil temperature beneath it. When the soil temperature at the depth where the leek maggot larvae are located exceeds 40°C and persists for more than 3 hours, it can effectively kill them.

II. Operational steps and technical points

(1) Cutting leeks. If the leeks are sparsely grown, and their roots and soil are easily visible, it is possible to skip cutting the leeks and directly erect a 30-centimeter-high arch shed on the ground, followed by covering the shed with plastic film. If the leeks are thriving, to prevent the leaves from shading and affecting sunlight exposure and soil heating, it is recommended to cut the leeks 1-2 days before covering the film. The stubble of the leeks should not be too long and should be kept as level as possible with the ground. If the stubble on the ground is too long, the newly grown leeks may not easily push through the old stubble, leading to slow growth, and even some weaker leek plants may die due to their inability to break through the old stubble.

(II) Mulching and soil pressing. From the end of April to mid-September, choose weather with strong sunlight (with a maximum light intensity exceeding 55,000 lux on the same day) for mulching, while avoiding extreme high temperatures to prevent plants from being damaged by sun exposure. It is best to choose a light blue non-drip film with good light transmittance, no water mist on the film, and a thickness of 0.10-0.12mm. After mulching, press the surrounding soil firmly to cover it. Due to the lower temperature at the junction of the film and the soil, if the roots of the leek are just at the edge of the film, there may be a small number of leek maggots that are difficult to kill. Therefore, it is recommended that the area of the film must be larger than the field area, and the film should extend about 50 centimeters beyond the edge of the field as much as possible.

(III) Remove the soil and uncover the film. When the temperature at a depth of 5 cm within the soil under the film consistently reaches above 40°C for more than 4 hours (i.e., cover the film before 8:00 am on the same day and uncover it around 6:00 pm), remove the plastic film. This will kill all the eggs, larvae, pupae, and adults of the leek maggot, and may even kill some other pests and diseases. If it suddenly becomes cloudy or the soil temperature is not high enough to kill the leek maggot after covering the film, the covering time can be extended until the soil temperature rises above 40°C to kill the leek maggot before uncovering. When the light is particularly strong, the maximum temperature at a depth of 5 cm in the soil is below 53°C, which has no effect on the growth of leek roots.

(4) Watering and Irrigation. After removing the mulching film, promptly water the seedlings to help them recover once the soil temperature has decreased. Throughout the growth process, maintain soil moisture.

The underground roots of the mulched leeks are not harmed, and new leaves will grow after 5-8 days. Compared to the unmulched leeks, the mulched leeks grow slowly in the early stage and accelerate in the later stage. After 20 days, there is no significant difference in growth height between the mulched and control leeks. For leeks in the root-raising period in summer, it is recommended to use the "solarization and mulching method" for maggot control before the end of May to avoid affecting the root-raising of leeks. For leeks harvested in summer, mulching can be done immediately after harvesting to kill maggots.

Attachment 2:

Key points of the "biological control method using entomopathogenic nematodes" prevention and control technology

This technology is safe, leaves no residue, has high efficacy, is easy to use, and is safe and harmless to humans, higher animals, plants, and the environment. It actively seeks out its host, has a long-lasting effect, and does not induce resistance.

1. Prevention and control mechanism

Entomopathogenic nematodes are specialized parasitic natural enemies of insects, effectively controlling various underground pests. After being used in the field, they actively seek out host pests and enter their bodies through the anus, stomata, internode membranes, etc. Subsequently, they release symbiotic bacteria, causing the host pest to die. Entomopathogenic nematodes can reproduce 2-3 generations inside the host. When the host's nutrients are depleted, the nematodes crawl out of the host and actively seek out new host insects, forming a sustainable nematode control strategy to effectively prevent and control underground pests in the field.

Control targets: underground pests such as the Chinese chive maggot (B. odoriphaga), grubs, peach fruit moth, cutworms, cabbage caterpillars, cutworms, long-horned beetles, Asian corn borer, mulberry longicorn beetle, or insects with underground stages throughout their entire life cycle.

II. Usage time and method

(1) Usage time

Prevention and control should be carried out 1-2 times a year, preferably in spring and autumn. For spring prevention and control, it is recommended to conduct it within 15 days before and after "May Day". Autumn prevention and control is crucial, and it should be carried out within 10 days before and after September 1st. The dosage of entomopathogenic nematodes is generally 800 grams per acre.

(II) Usage

1. Before secondary dilution, dilute the nematode preparation to prepare the mother solution.

2. After dilution, evenly mix the entomopathogenic nematodes into the water, and then pour it into the leek field along with the irrigation water. The method of pouring should be the same as that for chemical pesticides.

III. Precautions

(1) Apply it during the initial stage of the emergence of the maggot larvae.

(2) Due to the impact of ultraviolet radiation on nematode activity, it should be applied on cloudy days or before 9 am or after 5 pm on sunny days to avoid the lethal effect of ultraviolet radiation on nematodes.

(III) Due to the tendency of nematodes to settle to the bottom after prolonged storage, the prepared mother solution should be thoroughly stirred before each dilution. The prepared solution should be applied within 10 minutes.

(IV) When this product needs to be stored for a long time, it can be placed in a refrigerator at around 5℃, but it should not be stored in a freezer at below zero temperatures.