Metanastes

Metanastes is a genus of beetles belonging to the Scarabaeidae family, specifically the Dynastinae subfamily. Known as root-feeding scarabs, these insects are significant agricultural pests, particularly in subtropical and tropical regions where they cause substantial damage to root systems of various economically important crops.

The primary hosts for Metanastes species include sugarcane, maize, sorghum, and various turf grasses. Larvae, commonly referred to as grubs, live below the soil surface, where they consume roots and basal stems. This feeding behavior disrupts the plant's ability to uptake water and nutrients, resulting in stunted development.

The life cycle of Metanastes involves an egg stage, three larval instars, a pupal stage, and the adult beetle phase. Eggs are laid in the soil, and the larvae develop underground for several months. Adults are nocturnal, showing high activity at night, and are often attracted to light, which makes light trapping a useful diagnostic tool for entomologists.

Symptoms of infestation include the wilting and yellowing of plants, followed by poor establishment and eventual plant death in severe cases. Damaged crops often show patchy growth across the field. Because the damage occurs underground, growers often do not realize an infestation is present until significant crop loss has already occurred, highlighting the need for preventative soil analysis.

Control strategies for Metanastes require a combination of cultural and chemical interventions. Key management practices include:

• Crop rotation to break the pest's life cycle.
• Tillage practices that expose larvae to predators and desiccation.
• Application of granular insecticides during the planting process to protect young root systems.
• Monitoring adult flight periods using light traps to time the application of contact pesticides.