Oryzaephilus mercator (Fauvel)
Taxonomic placing: Insecta, Holometabola, Coleoptera, Sylvanidae.
Common name: Merchant grain beetle.
Geographical distribution: Cosmopolitan due to international trade in unprocessed cereals, oil cakes and grains from other stores.
Host plants: Various seeds that contain oil, grains, and in Western Africa, seeds of the African mango, Zwingia gabonensis Baillon, water melon, Citrullus lanatus Thunberg, and groundnut, Arachis hypogaea (L.).
Morphology: The adult is dark-brown, slender, 3-4 mm long. The thorax bears 6 lateral, saw-like protuberances and 2 longitudinal dorsal furrows. Elytra with longitudinal striations and with punctuations. The larvae are about 5 mm in length, white-grey, head brown and with 3 pairs of legs.
Life history: Females lay 300-400 eggs each, singly or in small groups in the substrate, in which the larvae develop. They complete a life cycle in 3-4 months at 20ºC, the optimum being at about 30–32·5°C. The pest does not survive at near saturation humidities. The adults can fly but rarely do, and their long distance dispersal occurs when infested products are transferred in commerce.
Economic importance: Both larvae and adults feed on various food products, especially those containing oil, such as oileeds, dried fruits, grains and even biscuits and cereals. They can gnaw through and enter sealed packaging, like plastic and cardboard boxes. Damaged products cannot be used in commerce. This beetle is a widespread and economically important household pest in Canada. In Western Africa O. mercator is a serious storage pest of tropical oilseeds, such as African mango, water melon and groundnuts. More recently the beetle infested dates in the south of Israel. This pest may be difficult to observe due to its slim body when hiding in cracks in the various products.
Management
Monitoring: Aggregation hormones are available for monitoring this pest.
Cultural methods: Sanitation and keeping the storage and production areas, as well as any packaging materials, clean and dry before storage. Using only strong packing material without any holes. Sieving in order to remove pest-containing damaged grains.
Controlled atmosphere: Wherever closed infrastructures exist, the combination of low oxygen and carbon dioxide-enriched atmospheres can be used to control stored product pests.
Commodity control: Wheat cultivars differ in their susceptibility to O. mercator, which prefers entire seeds and bran over these foods in pulverized form.
Chemical control: Fumigation with sulfuryl fluoride killed all insects exposed at 25°C within one day.
References
Arbogast, R. T. 1976. Population parameters for Oryzaephilus surinamensis and O. mercator: effect of relative humidity. Environmental Entomology 5: 738-742.
Baltaci, D., Klementz, D., Gerowitt, B., Drinkall, M.J. and Reichmuth, C. 2008. Sulfuryl fluoride against all life stages of rust-red grain beetle (Cryptolestes ferrugineus) and merchant grain beetle (Oryzaephilus mercator). Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, Florida, USA, 2008, pp 87.1-87.3.
Friedman, A.L.L. 2015. The Silvanidae of Israel (Coleoptera: Cucujoidea). Israel Journal of Entomology 44–45: 75–98.
Joshi, G.P. 1974. The biology of Oryzaephilus mercator F. on different varieties of wheat. Journal of Applied Entomology 77: 121-126.
Loschiavo, S.R. 1976. Food selection by Oryzaephilus mercator (Coleoptera: Cucujidae). The Canadian Entomologist 108: 827-831.
Loschiavo, S.R. and Sabourin, D. 1982.The merchant grain beetle, Oryzaephilus mercator (Silvanidae: Coleoptera), as a household pest in Canada. The Canadian Entomologist 114: 1163-1169.
Okiwelu, S.N., Dudu, P.O. and Lale, N.E.S. 1998. The effects of photoperiod on some aspects of the biology of Oryzaephilus mercator (Fauvel) (Coleoptera: Silvanidae). Journal of Stored Products Research 23: 189-193.
Pierce, A.M., Pierce Jr. H.D., Borden, J.H. and Oehlschlager, A.C. 1989. Production dynamics of cucujolide pheromones and identification of 1-Octen-3-ol as a new aggregation pheromone for Oryzaephilus surinamensis and O. mercator (Coleoptera: Cucujidae). Environmental Entomology 18: 747-755.
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