Holotrichia parallela

Systematic position: Holotrichia parallela is a species of beetle belonging to the order Coleoptera and the family Scarabaeidae. This insect is recognized as a major soil-dwelling pest, particularly prevalent in East Asian agricultural landscapes, where it poses a persistent threat to crop stability.

Host crops: This beetle is polyphagous, meaning it feeds on a wide range of plants. Key affected crops include legumes such as soybeans and peanuts, root crops like potatoes and sweet potatoes, as well as various grains and fruit tree seedlings. Both the subterranean larval stage and the aerial adult stage contribute to agricultural damage.

Biology and lifecycle: The lifecycle of Holotrichia parallela typically spans one to two years. Adult beetles emerge from the soil to mate and feed on foliage before females return to the soil to lay eggs. The larvae develop through three instars, living underground and feeding on roots and organic matter throughout their growth, which makes them difficult to detect until damage becomes severe.

Damage and pest status: The primary economic damage is caused by the larval stage, which consumes the root systems of crops. This destruction leads to stunted growth, reduced nutrient uptake, and the sudden death of plants. Because they feed beneath the surface, significant infestations can cause large patches of crops to wither before the damage is fully realized by the farmer.

Control measures: Integrated Pest Management (IPM) is essential for controlling this beetle. Recommended practices include:

• Deep plowing to expose larvae to natural predators and environmental stressors;
• Applying granular insecticides in the soil at planting time;
• Utilizing biological control agents such as entomopathogenic fungi (e.g., Metarhizium or Beauveria) to reduce larval populations naturally.