The scientific name of this pest is *Gryllotalpa unispina* Saussure, belonging to the order Orthoptera and family Tettigoniidae. It is commonly known by several names, including "single hedgehog," "big clam," "lara clam," "teriyao," "earth dog," and "ground dog." This species is typically found north of 32°N latitude.
From April to November, it primarily infests fields where crops such as cereals, tobacco, sweet potatoes, melons, and vegetables are planted. The larvae and adults feed on seeds, seedlings, and young shoots, causing significant damage. Their feeding activity disrupts the root systems of plants, leading to dehydration and eventual death of the seedlings. In addition, their burrowing in the topsoil creates tunnels that separate roots from the soil, further worsening the damage. Greenhouse conditions, with higher temperatures and early plantings, can lead to even more severe infestations.
Adult females measure 45–66 mm in length, while males are slightly smaller, ranging from 39–45 mm. The body color is generally brown with a dark brown head. The head is oval-shaped, with oval compound eyes and three simple eyes. The antennae are long and filamentous. The thoracic shield is shield-shaped, with a curved front edge and a distinct heart-shaped red spot on the back. The forewings are yellowish-brown, flat, and only cover part of the abdomen, while the hind wings are longer and rolled into a tube. The front legs are well-developed, while the middle and hind legs are smaller. The hind feet have a small gap between the inner edges, distinguishing them from other similar species. The eggs are oval, measuring 1.6–1.8 mm, and range in color from yellow-white to yellow-brown. There are 12 nymphal stages, with the first five stages resembling adults in shape and color.
This species has a life cycle that lasts approximately three years. In regions like Beijing, Shanxi, Henan, and Anhui, overwintering nymphs or adults become active in spring, with adults beginning to lay eggs in June. Nymphs hatch in mid-to-late June and progress through several molts before entering their third year. By October and November, they reach the 8- to 9-year-old stage. In the second year, they remain active in the upper soil layers during April. After 3–4 molts, they prepare for winter again. In the third year, they emerge in spring and mature by mid-August. Adults then molt once more, becoming fully developed and remaining active until the fourth year. Reproduction continues from June to August, with each female laying around 288–368 eggs over a one-month period. After guarding the third-stage nymphs, adults become nocturnal and exhibit phototactic behavior.
Control measures include applying fully decomposed organic manure, using light traps, and monitoring populations. When there are 0.3–0.5 individuals per square meter, it's considered moderate, and above 0.5 indicates serious infestation requiring action. Poison baits can be applied at sowing time, and during the growing season, baits mixed with insecticides like trichlorfon are effective. For example, 4–5 kg of bait per 667 m², mixed with a 30 times diluted solution of 90% trichlorfon, can be used. Irrigation with insecticides like phoxim or parathion during the growing season is also recommended. Additionally, granular formulations such as 6% Myda can be mixed with fine soil and applied at a rate of 5008 per 667 m². These methods help reduce infestation and protect crops effectively.
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