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Adult saw-toothed grain beetle, Oryzaephilus surinamensis. ©Clemson University, USDA Cooperative Extension Slide Series, Bugwood.org

Dorsal view of adult O. surinamensis (museum set specimen). ©Georg Goergen (source CABI CPC)

Oryzaephilus surinamensis (Linnaeus, 1758) - Saw-toothed Grain Beetle

Summary

The saw–toothed grain beetle is found all over the world. It is a pest of a variety of stored foods including cereals, cereal-based products, but also copra, spices, nuts and dried fruit. Both adults and larvae feed on externally on maize grains. They are unable to feed on undamaged grains.

Common Names

Saw-toothed grain beetle

Synonyms

Colydium frumentarium Fabricius, 1792; Dermestes sexdentatus Fabricius, 1792; Dermestes surinamensis Linnaeus, 1758; Silvanus bicornis Erichson, 1846; Silvanus surinamensis Linnaeus, 1758

Taxonomic Position

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

Origin and Distribution

The saw-toothed grain beetle is distributed throughout the world and frequently transported in grain products.

Description

The saw-toothed grain beetle is a slender dark brown beetle 2.4-3 mm in length, with a flattened body, and six saw-toothed projections (“teeth�?) on each side of the prothorax. The abdomen tapers towards the tip and it rarely flies. Its antennae are long and moniliform (“bead-like").

Its eggs are white to yellow-ochre, capsule -shaped and about 0.7 mm long.

The larva is elongate yellowish-white with a brown head, has numerous setae (hairs) and three pairs of legs. They are about 0.8 mm when newly hatched and 3 – 4 mm when fully developed.

Similar Species

Oryzaephilus mercator (Fauvel), the merchant grain beetle, is nearly indistinguishable from the saw-toothed grain beetle, O. surinamensis in appearance. Small differences in the shape of the head and in their genitalia are used to differentiate them. The saw-toothed grain beetle is more commonly found on cereals while the merchant grain beetle prefers oil-seed products.

Life Cycle

The female saw-toothed grain beetle lays eggs singly or in small batches in the food product. She lays about approximately 400 eggs in her lifetime. The eggs hatch in 3-8 days. Larvae are free-living and usually pass through four instars. They are unable to feed on undamaged grains. The life cycle takes from 20-80 days dependent on temperature and the adults usually live around 6 to 10 months. Adults normally disperse by walking but can fly at dawn and dusk in warm conditions. Long distance dispersal takes place in contaminated foodstuffs.

Pest Destructive Stage

Adult and larva

Host Range

Attacks cereals, cereal-based products, but also copra, spices, nuts, dried fruit.

Host Lifestage Affected

Post-harvest

Host Plant Part Affected

Fruits, pods, seeds and grain

Damage Symptoms

Seeds and grains: feeding; visible mould, contamination with faeces and dead bodies.

Pest Management

Detection methods
The saw-toothed grain beetle can be detected by visual inspection. A grain probe has been developed which provides a convenient method to monitor this pest in bulk grain stores.

Cultural practices
The severity of a saw-toothed grain beetle infestation can be reduced by good store hygiene which includes cleaning the store between harvests, immersing grain sacks in boiling water and fumigating the store to eliminate residual infestations, ensuring that all spillages are removed, all cracks and crevices in the store are filled and the selection of only uninfested material for storage. Infestations of this species may also be limited by the storage of good quality grains such as whole cereals with fewer broken grains.

Physical control

The removal of adults and larvae from the grain by sieving can reduce populations but this is very labour-intensive. The addition of inert dusts such as ash and clay to the grain can reduce insect numbers by causing the insects to die from desiccation.

Biological control

Biological control has not been practiced against Oryzaephilus species apart from in controlled field trials.

Controlled atmosphere
Where suitable infrastructure exists, low oxygen and carbon dioxide-enriched atmospheres can be used to control stored product pests.

Freezing and Heating
Where the infrastructure exists, freezing for several days and heating for 24 hours have proved to be effective control methods for stored product pests.

Chemical control

The saw-toothed grain beetle is susceptible to all the insecticides normally used on stored food. Fumigation of grain stocks with phosphine will control existing infestations but will not protect against re-infestation. Pesticides are poisons so it is essential to follow all safety precautions on labels.

Sources of Information and Links

AVA (2001). Diagnostic records of the Plant Health Diagnostic Services, Plant Health Centre, Agri-food & Veterinary Authority, Singapore. 1973-1998. Data mined from CAB Abstracts database, years 1973 to 1998. Wallingford, UK: CAB International

Champ B.R. and Dyte C.E. (1976). Report of the FAO Global Survey of Pesticide Susceptibility of Stored Grain Pests. FAO Plant Production and Protection Series No 5. Rome, Italy: Food and Agriculture Organization of the United Nations.

Cook D.A. and Armitage D.M. (2000). Efficacy of a diatomaceous earth against mite and insect populations in small bins of wheat under conditions of low temperature and high humidity. Pest Management Science, 56(7):591-596.

Epsky N.D. and Shuman D. (2001). Laboratory evaluation of an improved electronic grain probe insect counter. Journal of Stored Products Research, 37(2):187-197.

Fields P. and Korunic Z. (2000). The effects of grain moisture content and temperature on the efficacy of diatomaceous earths from different geographical locations against stored-product beetles. Journal of Stored Products Research, 36(1):1-13.

Gorham J.R. (1991). Insect and mite pests in food. An illustrated key. Vol. 1 and 2. US Department of Agriculture, Agriculture Handbook Washington, DC, USA.

Haines C.P. (1991). Insects and arachnids of tropical stored products: their biology and identification (a training manual). Chatham, UK: Natural Resources Institute.

Krischik, Vera: Stored Product Management; Stored-product Insects and Biological Control Agents, page 92. USDA-ARS and the University of Wisconsin, 1995

Mallis A. (1990). Handbook of Pest Control. 7th edition. Cleveland: Franzak & Foster Co., pp. 524-6.

PaDIL – Plant Biosecurity Toolbox. Sawtoothed grain beetle Oryzaephilus surinamensis. http://www.padil.gov.au/pbt. Accessed on 12 Jun 2011.

Trematerra P., Sciarreta A. and Tamasi E. (2000). Behavioral responses of Oryzaephilus surinamensis, Tribolium castaneum and Tribolium confusum to naturally and artificially damaged durum wheat kernels. Entomologia Experimentalis et Applicata, 94(2):195-200.

Saw-toothed Grain Beetle". Forest Health and Monitoring Division. Maine Department of Conservation. 2007-04. http://maine.gov/doc/mfs/sawtooth.htm. 23/12/2010

Waterhouse D.F. (1993). The major arthropod pests and weeds of agriculture in Southeast Asia. Canberra, Australia: ACIAR.

Weston P.A. and Rattlingourd P.L. (2000). Progeny production by Tribolium castaneum (Coleoptera: Tenebrionidae) and Oryzaephilus surinamensis (Coleoptera: Silvanidae) on maize previously infested by Sitotroga cerealella (Lepidoptera: Gelechiidae). Journal of Economic Entomology, 93(2):533-536.

Editors

Anne M. Akol, Makerere University; Maneno Y. Chidege, Tropical Pesticides Research Institute; Herbert A.L. Talwana, Makerere University; John R. Mauremootoo, BioNET-INTERNATIONAL Secretariat.

Acknowledgments

We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

Contact

BioNET-EAFRINET Regional Coordinator: [email protected]



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