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How to prevent land tigers
The scientific name of this pest is *Trachea tokionis* (Butler), previously known as *Agrotis tokionis* Butler. It belongs to the family Noctuidae, under the order Lepidoptera. Common names include black worm, silkworm, cutworm, and various regional variations. This species is widely distributed across China, ranging from northern Heilongjiang and Inner Mongolia down to Fujian, Jiangxi, Hunan, Guangxi, and Yunnan.
The primary hosts of *T. tokionis* include vegetable seedlings, corn, tobacco, cotton, and fruit trees. The larvae are particularly damaging during their early developmental stages, often feeding on young plants and causing significant damage.
Morphologically, the adult moth has a body length of 20–22 mm and a wingspan of 45–48 mm. The head and thorax are brown, with two dark spots on the outer edge of the lower lip. A dark horizontal line runs across the neck plate. The abdomen is grayish-brown, with a dark brown central area on the forewing. The wings feature a double brown base line, wavy inner lines, and a black-edged sword-shaped pattern. The hind wings are light yellowish-brown.
Eggs are hemispherical, measuring approximately 1.8 mm in length and 1.5 mm in height. They start off pale yellow and turn grayish-brown before hatching. Mature larvae can grow up to 41–61 mm long, with a yellow-brown coloration and wrinkled skin. Their heads are brown, featuring two dark vertical stripes and a triangular marking on the front lip. The abdominal segments have similar sizes, and the prolegs are long and dark brown, except for the tips of the bristles, which are slightly yellowish.
The pupal stage lasts about 23–29 mm, initially light yellow and turning yellowish-brown as it matures.
In terms of behavior, the larvae overwinter in the top soil layer among weeds and green manure fields. In the Yangtze River region, they emerge in early March and begin feeding in May. When temperatures exceed 20°C, they enter diapause in summer and re-emerge in mid-September. Adults emerge in mid-October, with each female laying around 1,000 eggs. The egg stage lasts 11–24 days, while the larval stage can extend for over 300 days.
For control, monitoring is essential. Blacklight traps or sweet-and-sour liquid traps can be used to monitor adult populations. In North China, trapping should begin between April 15 and May 20. If more than 5–10 moths are caught per day, it indicates an upcoming peak. Larval density can also be assessed through field surveys—0.5–1 larvae per square meter before planting or 0.1–0.3 after planting is a threshold for intervention.
Agricultural practices such as removing weeds in early spring help reduce oviposition sites. If larvae are found, weeding combined with spraying can prevent them from burrowing into the soil. Weeds removed should be composted away from the fields.
Trapping methods include blacklight traps, sweet-and-sour liquid traps (e.g., 6 parts sugar, 3 parts vinegar, 1 part alcohol, 10 parts water, plus 9 parts trichlorfon), and bait traps for larvae. Fermented fruits or vegetables can also be used with added pesticide. Additionally, certain weeds like chrysanthemum, thorny vegetables, and wormwood can be used to attract and trap larvae.
Chemical control is effective for 1st to 3rd instar larvae, which are more vulnerable. Spraying options include 40.7% chlorpyrifos emulsifiable concentrate at 90–120 g per 667 m², diluted in 50–60 kg of water, or 2.5% deltamethrin at 3000 times dilution. Other options include 20% fenvalerate, 20% cypermethrin, 10% trichlorfon at 2000 times, and 50% phoxim at 800 times. Soil treatment with 3% malathion granules at 2–5 kg per 667 m² is also recommended. For detailed application guidelines, refer to local agricultural extension resources.