Tribolium castaneum (Herbst)
Common name: Red flour beetle.
Geographic distribution: Worldwide, but more common in warmer regions. This pest occurs in temperate areas, where it survives winters in protected places, especially with central heating.
Host plants: Grain products, dried foods, pet foods and dried flowers.
Morphology: Body of adults flat, reddish-brown, about 3-4 mm long, thorax slightly darker then the elytra, densely punctated. Elytra with punctate, parallel-sided striations. Last three antennal segments larger than all others, almost square. Larvae initially whitish, later becoming brown, length up to 5 mm, terminal abdominal segment bears a pair of dark, upturned projections.
Life history: The adult is long-lived, sometimes living more than three years. The females mate several times, and may lay 300-600 eggs which are covered with a sticky material to which flour particles adhere. The hatched larvae feed on any available food for about 3-4 weeks and pupate. A life cycle requires 7 to 12 Weeks, dependent on the prevailing temperatures; the optimum conditions are 35°C and 60-80% relative humidity. These beetles can disperse by flight.
The genome sequence of Tribolium castaneum has been described.
Economic importance: A major pest of stored products, especially in warmer climates. It infests mostly seeds, kernels and other products, usually those that had already been wounded by other pests or damaged during harvest and storage. The affected product becomes contaminated with faeces, and the increased humidity promotes molding. Economic losses consist of reduced weight and product quality, difficulties in baking, reduced marketability of infested products and an accompanying unpleasant smell. Pest presence may cause allergic responses.
Management Monitoring: Placing simple traps baited with damaged seeds or cereals, or with a pheromone. Presence of holes in grains and seeds and the dust due to pest feeding.
Physical control: Sanitation, removal and destruction of any potential sources of infestation, including all grain products, pet foods, nuts, spices and other dried foods. Cleaning small bits of grain that have fallen from leaking packages. If infestations are found, the store or shelves should be vacuumed and the area around the infestation thoroughly cleaned. Reducing pest numbers by sieving, or by adding inert dusts to the grain bulk, which causes pest death by desiccation. Suspected grain products may be stored in containers with tight fitting lids, or in a freezer for 4-5 days, or, if possible, at temperatures of 50°C. Modified atmosheres, reducing the O2 levels and increasing those of CO2, or vacuuming, are applicable in closed spaces or spaces that can be sealed by plastic sheets. The application of Diatomaceous earth (DE) to adult T. castaneum infesting wheat resulted in 100% pest mortality, only in 60-80 % in maize. Beetle populations originating from different European regions differed in their susceptibility to DE.
Chemical control: Tribolium castaneum has developed resistance to many common pesticides, whose intensity differs in different regions. Direct applications of a pyrethrin aerosol on the beetle resulted in almost 90% mortality, but less when applied onto infested flour. Treating pest larvae with insect growth regulators (IGRs) resulted in malformed beetles or in much reduced adult emergence. Control was also achieved with a pyrethroid alone or when combined with an IGR, and with spinetoram. Essential oils extracted from cinnamon (Cinnamomum aromaticum Nees) and impregnated on filter paper discs strongly repelled the beetle.
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Arthur, F.H. 2015 Residual efficacy of pyrethrin + methoprene for control of Tribolium castaneum and Tribolium confusum in a commercial flour mill. Journal of Stored Products Research 64: 42-44.
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Huang, Y and Ho, S. H. 1998. Toxicity and antifeedant activities of cinnamaldehyde against the grain storage insects, Tribolium castaneum (Herbst) and Sitophilus zeamais Motsch. Journal of Stored Products Research 34: 11-17.
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Ridley, A., Hereward, J.P., A. Daglish, G.J., Raghu, S., Collins, P.J. and Walter, G.H. 2011. The spatiotemporal dynamics of Tribolium castaneum (Herbst): adult flight and gene flow. Molecular Ecology 20: 1635–1646.
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