One, the main pests
1. This pest is also known as lala or earth dogs. Both adult crickets (with fully developed wings) and nymphs (immature stages) are harmful to potato crops. They use their mouthparts and large front legs to tear the underground stems or roots of potatoes, causing wilting or even death of the above-ground parts. In some cases, they eat the buds, preventing them from growing and leading to a lack of seedlings. These pests also dig tunnels in the soil, separating the root system from the soil, which increases air exposure and causes water loss. This affects seedling growth and can lead to plant death. In the fall, they feed on tubers, creating holes that make them more susceptible to decay and rot.
Adult and nymph earthworms move vertically in the soil depending on temperature changes. During winter, they burrow 1.2 to 1.6 meters deep to create nests for hibernation. In spring, as temperatures rise, they move up to about 10 cm in the tillage layer. They are active at night and rest underground during the day. In summer, when it gets hot, they go deeper—about 20 cm. In the fall, they return to the tillage layer to cause damage. They prefer areas with more organic matter and tend to avoid salty soils.
2. Another pest is known as the ground silkworm, which is the larval stage of a beetle. In potato fields, it mainly damages the tender roots, underground stems, and tubers by chewing and boring into them. This results in the disruption of nutrient and moisture supply, causing the above-ground plants to wilt and die. Tuber damage leads to quality loss or rot. Adult beetles also fly onto the plants and feed on the leaves.
Cockroaches and their adults both overwinter and move vertically in the soil. Adults typically stay less than 40 cm below the surface, while larvae overwinter deeper, around 90 cm. In spring, they rise back to about 10 cm. They are attracted to organic matter and often live in manure. Adults are nocturnal, hiding in the soil during the day. Larvae have three pairs of legs, a plump body, and are milky white, often curled in a horseshoe shape, entering a state of dormancy.
3. The golden wireworm, also called a wireworm, is the larval stage of a click beetle. In spring, these larvae bore into the buds, roots, and underground stems of potatoes. Thicker roots or stems are rarely snapped, but the seedlings gradually wilt and die. In the fall, they bore into tubers, creating holes that reduce the quality of the potatoes and sometimes cause rot.
Both adult and larval wireworms burrow into the soil up to 60 cm deep in winter to survive. They leave small tunnels and return to the tillage layer in spring. When the soil temperature exceeds 17°C in summer, they move downward again. In the fall, as surface temperatures drop, they return to the crop layer. Newly hatched larvae are white, and as they grow, they change color, becoming shiny and hard. They are slender, measuring 2 to 3 cm in length.
4. The ground tiger, also known as the cutworm, is a type of caterpillar. The large larvae are the most damaging. Adult moths are nocturnal and come in two types: small tigers and yellow tigers. Ground tigers primarily harm potato seedlings by cutting them off near the soil surface, killing entire plants and often dragging them into burrows. Young larvae also feed on young leaves, creating nicks and holes. They can also damage tubers by making small holes.
Ground tiger larvae are yellow-brown, dark brown, or black-brown, usually 3 to 5 cm long. Small tigers prefer moist, weedy environments with high soil moisture, while yellow tigers thrive in drier conditions and are sensitive to heat. Their adults are attracted to light and molasses.
Second, control methods
The aforementioned underground pests vary in species, but they share similarities. All are active underground, so prevention and control methods are generally similar.
1. Deep plowing in autumn helps destroy their overwintering habitats. This method can freeze and kill many larvae, mites, and adults, reducing the population for the following year.
2. Field sanitation is important. Removing weeds, debris, and trash from fields, land, and ditches reduces the number of eggs and larvae present.
3. Trapping adult pests can be effective. Using molasses traps, black light lamps, fresh horse dung piles, or grass clippings can attract and kill adults, reducing egg-laying and subsequent larval populations.
4. Chemical control includes using poisoned soil and granules. During sowing, apply 1% trichlorfon powder at 3–4 kg per acre mixed with 10 kg of fine soil, or use 3% carbofuran granules at 1.5–2 kg per acre. Apply these directly into furrows to poison the pests. Alternatively, spray the pesticides on the roots of seedlings during cultivation to target the pests.
Irrigation is another option. Use a 40% phoxim solution diluted 1500–2000 times and apply 50–100 ml per plant during the seedling stage.
Bait application is also effective for small areas. Mix the pesticide with fried wheat bran, cornmeal, or bran to create baits, and spread them in the field at night to attract and kill the pests.
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