Cadelle beetle

The Cadelle beetle (Tenebroides bipustulatus) is a member of the Trogossitidae family within the Coleoptera order. Adult beetles have a flattened, elongated, dark brown or black body typically measuring 6–10 mm in length.

A key identification feature is the presence of two distinct light spots on the pronotum. The beetle possesses strong, prominent mandibles, which are powerful enough to bore through tough materials like wooden structures or hard grain kernels.

The larvae are cream-colored with a darkened head, growing up to 15–20 mm long. Their bodies are sparsely covered with hairs, aiding their movement through grain masses and debris.

The life cycle involves complete metamorphosis, moving through egg, larval, pupal, and adult stages. The duration of this cycle depends heavily on the temperature and moisture levels of the storage environment.

These beetles are known for their secretive behavior, often hiding deep within cracks, crevices, and behind grain storage equipment, making them difficult to detect during routine inspections.

The Cadelle beetle primarily feeds on cereal grains such as wheat, barley, rye, corn, and rice. It also infests processed grain products, including flour, semolina, and cereal meals.

This pest is noted for its dual nature as both a primary feeder and a predator. While they destroy grain kernels by hollowing out the embryo, the larvae also hunt and consume other stored-product insects, such as flour beetles.

Economic damage is caused by the loss of viability in seed grain and the general contamination of food supplies with excrement and cast-off larval skins.

In addition to direct feeding, their tunneling behavior damages the structural components of storage facilities. They are also known to introduce secondary moisture into grain piles, encouraging mold growth.

Large populations can cause significant spoilage of grain stocks, rendering them unsuitable for human consumption or processing into high-quality food products.

The Cadelle beetle thrives in climate-controlled environments like warehouses, flour mills, and grain silos. In stable conditions, they can produce multiple generations per year.

The optimal developmental conditions for this pest are temperatures ranging from 22°C to 28°C and grain moisture levels exceeding 14 percent.

Summer months, which bring increased temperatures to storage areas, typically see the fastest reproductive rates for this species, leading to sharp population spikes.

During colder seasons in unheated facilities, the beetles slow their metabolic activity but are capable of surviving harsh conditions by retreating into protected voids in the storage architecture.

Dissemination usually occurs via the movement of infested grain shipments or the transfer of equipment and transport containers that have not been properly cleaned and disinfected.

An early sign of infestation is the presence of hollowed-out kernels, particularly around the germ area, which is easily visible when inspecting samples under magnification.

The presence of fine dust, excrement, and silk threads within the grain mass or along the floor corners of storage bins often indicates a well-established colony of Cadelle beetles.

A musty, stale odor emerging from the grain stock is a strong indicator of heavy pest infestation, often accompanied by the growth of microorganisms in the waste-polluted areas.

Detection is often confirmed through grain probe sampling and sifting, which reveals both larvae and adult beetles hidden within the deeper, darker sections of the grain pile.

Increased temperature within specific hotspots in the silo can signify intensive pest activity, requiring immediate action to prevent the spread of the infestation.

Sanitation is the first line of defense; regular cleaning of warehouses and grain handling equipment removes the hiding spots and residual grain that support beetle populations.

Surface treatments with approved residual insecticides are essential for disinfecting the empty storage structures and perimeter areas prior to the arrival of new grain.

Fumigation using phosphine-based products is the most effective method for controlling established infestations. Fumigants can penetrate deep into the grain mass to reach larvae and adults in all hidden crevices.

Maintaining low grain moisture levels (below 13 percent) and utilizing aeration systems to keep grain temperatures cool will significantly inhibit the pest's reproductive capabilities.

• Monitoring with pheromone-baited traps
• Routine sampling and laboratory screening of incoming grain
• Strict quarantine of any grain batches suspected of infestation