Grain beetle (Sitophilus granarius)

Size:

• 2.5 to 5 mm long
• Slender, cylindrical body

Look:

• colored brown to reddish-brown
• Long, curved trunk (snout)
• No elytral spots (unlike rice or maize weevils)
• Wingless, cannot fly
• Antennas are club-shaped and angled to the side.

Way of life:

• They mostly live inside grain silos, warehouses, or storage containers.
• Females use their proboscis to bore into a grain and lay an egg inside.
• The larva eats the inner part of the grain; development is complete within the grain.
• The larva pupates in the cavity and emerges as an adult beetle.

Reproduction:

• Egg-laying capacity: 200 to 300 eggs per female
• Development time depends on temperature: 5 to 12 weeks
• Several generations per year under favorable conditions
• No winter dormancy in heated buildings

Infestation sites:

• Whole grains: wheat, rye, barley, oats, corn
• Occasionally also rice or buckwheat.
• Infestation is most common in dark, damp, warm storage locations.
• Primarily in silos, grain stores, feed stores, mills or pantries

Nutrition:

• Exclusively plant-based
• Whole grains as the main food source
• Larvae feed on the inner endosperm tissue of the grain.
• Adult animals also eat outer layers, germ, and flour residue.

Behave:

• Mostly hidden in the grain or on the storage floor
• No active escape behavior
• Major damage is caused unnoticed by larvae in the grain.
• Slow movements at room temperature, faster when warm
• No light requirement for reproduction

Economic damage:

• Destruction of stored goods by completely hollowing out the grains
• Loss of quality due to flour dust, contamination, heat generation
• High losses during storage without regular monitoring

Hygiene risks:

• Food contamination by beetle remains, droppings and flour dust
• Health risks to humans and animals from consuming contaminated products
• Spread through transport, packaging and storage

Infestation dynamics:

• Undetected infestations can spread massively within a few weeks.
• Heat generated by mass infestation promotes further development
• Combination with other stored-product pests such as flour moths or molds is possible.

Disease transmission:

• Transport of microorganisms
• Concentration of foods

Storage hygiene:

• Keep storage areas dry, cool and well-ventilated
• Regularly turn and check the grain.
• Store supplies in well-sealed, airtight containers.
• Completely empty and clean old stock before refilling.

Monitoring:

• Sticky traps and beetle traps in the warehouse
• Visual inspections and sieve samples for infestation detection
• Temperature and humidity measurement in grain piles

Behave:

• Do not store open grain products.
• If boreholes or flour dust are spotted: act immediately.