Cadelle beetle

The Cadelle beetle (Tenebroides mauritanicus) belongs to the family Trogositidae of the order Coleoptera. Adult beetles are elongated and flat, typically measuring 8–10 mm in length.

The adult body is a shiny dark brown to black color. A distinguishing morphological feature is the loose connection between the pronotum and the elytra, which gives the beetle a unique, somewhat flexible appearance.

Larvae are quite large, reaching up to 15–20 mm. They are off-white with a dark head and feature two distinctive dark, hardened hooks at the tip of the abdomen, making them easily recognizable.

The life cycle involves complete metamorphosis, including egg, larva, pupa, and adult stages. Depending on environmental conditions, they can produce one or more generations per year within a granary.

Adult Cadelle beetles are known for their longevity and durability, often surviving for several years, which allows them to persist in storage structures for extended periods if left untreated.

This beetle is a serious pest of stored products, commonly found in granaries, warehouses, and mills. It infests a wide range of goods, including wheat, corn, rice, barley, oats, and processed items like flour.

Uniquely, the Cadelle beetle is also a predator. Larvae and adults may feed on other stored-product insects, such as flour beetle larvae, though the damage caused to the grain significantly outweighs this beneficial impact.

The primary damage occurs when the beetles and larvae feed on the germ of the grain kernel. This makes the grain unusable for seed purposes and lowers its overall commercial and nutritional value.

In addition to feeding on food products, the larvae are notorious for boring into wooden structures, such as warehouse beams and floorboards, to build pupal cells. This creates structural damage in addition to product contamination.

Infested food items often become contaminated with insect excrement and debris, leading to a foul odor that renders the entire batch unacceptable for human or animal consumption.

Visual identification of an infestation involves observing irregular, ragged holes in grain kernels, which indicates that the beetles have been actively feeding on the internal endosperm.

Evidence of larval activity can often be found by examining wooden beams in the storage facility. Small holes accompanied by fine wood shavings (boring dust) indicate where larvae have burrowed for pupation.

A high level of infestation is characterized by the presence of dark excrement and cast-off larval skins mixed into the bulk grain or flour, making the product appear dirty and degraded.

An unpleasant, musty, or rancid smell in a storage facility is a classic sign of high insect activity, particularly when larvae have infested wooden structures and grain masses simultaneously.

In grain silos, the presence of the beetles can be detected by examining the grain surface or using pitfall traps placed in the grain mass to monitor for adult movement.

The most important control measure is strict sanitation. All debris, dust, and leftover grain should be removed from empty bins, floors, and machinery before new grain is brought into the facility.

Maintaining the moisture content of grain at or below 14% significantly reduces the likelihood of an infestation, as high moisture facilitates the development of both the beetles and secondary mold.

Regular inspection of wooden warehouse components is necessary. If wood is heavily infested with larval borings, it should be replaced or treated with suitable contact insecticides to prevent re-infestation.

For established infestations in stored grain, fumigation with registered grain fumigants (such as phosphine) is the most effective way to eliminate the pest population in all life stages.

Using structural barrier sprays and maintaining cool temperatures within the storage facility are key strategies to prevent the Cadelle beetle from colonizing a new warehouse environment.