Insecticidal efficacy of diatomaceous earth against Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium confusum du Val (Coleoptera: Tenebrionidae) on stored wheat: influence of dose rate, temperature and exposure interval |
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Authors: | CG Athanassiou BJ Vayias NG Kavallieratos CTh Buchelos |
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Affiliation: | a Laboratory of Agricultural Zoology and Entomology, Agricultural University of Athens, 75 Iera Odos, Athens 11855, Greeceb Laboratory of Agricultural Entomology, Department of Entomology and Agricultural Zoology, Benaki Phytopathological Institute, 8 Stefanou Delta, Kifissia, Attica 14561, Greecec Laboratory of Efficacy Evaluation of Pesticides, Benaki Phytopathological Institute, 8 Stefanou Delta, Kifissia, Attica 14561, Greece |
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Abstract: | Laboratory experiments were conducted in order to assess the insecticidal effect of a diatomaceous earth formulation (Silicosec®, Biofa GmbH, Germany) against Sitophilus oryzae and Tribolium confusum on stored wheat. Adults of the two species were exposed on wheat treated with diatomaceous earth at four dose rates: 0.25, 0.5, 1 and 1.5 g/kg of wheat, respectively. For each dose rate, the treated wheat was placed at 22°C, 25°C, 27°C, 30°C and 32°C. Dead adults were counted after 24 and 48 h, 7 and 14 d of exposure. After the 14-d interval, the live adults were removed and placed for 7 d in untreated wheat (in the case of S. oryzae) or untreated flour (in the case of T. confusum), and the production of F1 was recorded. For both species, dose rate, temperature and exposure interval significantly affected mortality (P<0.001). Mortality was higher at longer exposure intervals. The efficacy of SilicoSec against S. oryzae increased with temperature, but for T. confusum mortality was lower at 32°C, compared to 30°C, for 24 and 48 h exposure intervals. Tribolium confusum proved less susceptible to SilicoSec than S. oryzae. In general, the rates of 1 and 1.5 g/kg of wheat provided a satisfactory level of protection against the two species examined. For S. oryzae, F1 emerged only at 22°C, in wheat treated with 0.25 or 0.5 g/kg. However, for T. confusum, F1 were recorded at 22°C for 0.5 g/kg and at 22°C, 25°C, 27°C and 30°C for 0.25 g/kg. |
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Keywords: | Diatomaceous earth Stored wheat Sitophilus oryzae Tribolium confusum Natural insecticides Inert dusts SilicoSec |
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