Formosan scarab beetle

Systematic position: The Formosan scarab beetle (Tocama formosana) belongs to the order Coleoptera and the family Scarabaeidae. Within the subfamily Melolonthinae, this species is recognized as a significant pest, particularly within its native and introduced habitats in East Asia.

Affected crops: This beetle is highly polyphagous, meaning it feeds on a wide variety of plant species. The adult stage primarily targets the foliage of broad-leaved trees, including fruit orchards and ornamental plants. The larvae, often referred to as white grubs, primarily damage the root systems of young trees and nursery stocks.

Biology and lifecycle: The lifecycle follows a complete metamorphosis: egg, larva, pupa, and adult. Eggs are laid in the soil where organic matter is abundant. Larvae spend the majority of their development underground, feeding on plant roots and decaying organic material, which can result in a multi-year generation cycle depending on climatic conditions.

Nature of damage and pest status: The pest causes significant economic impact through both root destruction and defoliation. Larval root feeding is the most destructive aspect, often causing seedlings to wilt and die. Adult beetles emerge to feed on canopy foliage, which, in cases of severe infestation, can lead to complete defoliation and tree decline.

Protection measures: Management of Tocama formosana requires an integrated pest management (IPM) strategy:

• Deep soil cultivation to disrupt the larval environment and increase mortality.
• Deployment of light traps to monitor and reduce adult beetle populations during peak flight.
• Application of targeted soil-active insecticides during the larval growth stages.
• Use of entomopathogenic nematodes or fungi as sustainable biological control agents.