Summary

The red flour beetle is found in most tropical and subtropical countries in the world. It is a pest of stored maize and a variety of stored products. Both adults and larvae feed on internally on maize grains.

Common Names

Red flour beetle, bran bug, rust red flour beetle, flour beetle, rust red flour beetle

Synonyms

Colydium castaneum Herbst 1797

Taxonomic Position

Phylum: Arthropoda; Class: Hexapoda (Insecta); Order: Coleoptera; Family: Tenebrionidae

Origin and Distribution

The red flower beetle is present in most tropical and subtropical countries in the world.

Description

The adult red flower beetle is approximately 3-4 mm long with a flattish curved-sided body which is reddish-brown in colour. The head and upper part of the thorax are covered with minute punctures and the wing cases (elytra ) are ridged along their length. The antennae are enlarged at the tip (capitate) with the last three segments wider than preceding segments. The eyes are reddish-black in colour.

Eggs are approximately 0.5 mm long, cylindrical and white or colourless. They are sticky which causes them to become covered in flour and stick to containers.

The larvae are yellowish-white, slender, and cylindrical and covered with fine hairs. The head is pale-brown and the last segment of the abdomen has two upturned dark, pointed structures.

The pupa does not have a cocoon and is yellowish-white, becoming brown later.

Similar Species

It is possible to confuse the red flour beetle (Tribolium castaneum) with the ‘confused flour beetle’ (Tribolium confusum). It is very difficult to distinguish between the larvae of both species. Adults of both species are similar in size and colouration but they can be distinguished by the following features among others: the eyes of the red flour beetle are larger and closer together than those of the confused flour beetle; the red flour beetle has a curved-sided thorax while the confused flour beetle has a straight-sided thorax ; the last three antennal segments of the red flour beetle are much broader than the previous segments while the antennal segments of the confused flour beetle gradually broaden. Adults of both species have well developed wings but only the red flour beetle has been observed to fly though it is not a strong flyer.

Life Cycle

Females lay between 300-400 eggs in their 5-8 month adult lifespan. Under optimum conditions of 35°C and 60-80% relative humidity, the development times for each stage are approximately 3 days for eggs, 16 days for larvae and 5 days for pupae. Both stages cause significant damage to grains that are already damaged physically or by the action of other pests. Adults move quickly and rapidly run for cover when disturbed. They can be found at the surface or deep within grain stores. Adults disperse over short distances through flight.

Pest Destructive Stage

Adult and larva which feed mainly on the germ of the cereal

Host Range

The red flour beetle has a very broad host range. It is a major pest of the following crops among others: maize, groundnut, oats, Brazil nut, barley, walnuts, lentil, rice, beans, peas, almond, rye, sorghum and wheat. The red flour beetle also attacks a wide range of dried stored products.

Host Lifestage Affected

Post-harvest and storage

Host Plant Part Affected

Fruits, pods, seeds, grains and vegetative organs

Damage Symptoms

Seeds and grains: internal feeding; contamination with faeces, promoting mould 

Pest Management

Chemical control

Organophosphates, pyrethroids and fumigants have been used to control red flour beetle. Tetrachlorvinphos was the most persistent insecticide used against the red flour beetle in Pakistan, followed by diazinon, malathion, azinphos-methyl and dichlorvos. The red flour beetle has developed resistance against a variety of insecticides in a number of countries. Pesticides are poisons so it is essential to follow all safety precautions on labels.

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