Evaluations of some bioagents against Sitophilus oryzaeunder laboratory and store conditions


Abstract: The effect of three microbial control agents Bacillus thuringiensis Berliner (Bacteria:Bacillaceae), Beauveria bassiana (Bals.-Criv.) Vuill. (Deuteromycotina: Hyphomycetes) andMetarhizium anisopliae (Metschnikoff) Sorokin (Deuteromycotina: Hyphomycetes) and threebotanical extracts, Taxodium distichum, Boswella carterii and Nigella sativa was evaluated onthe rice weevil Sitophilus oryzae (L.) (Coleoptera: Curculionidae) under laboratory and storeconditions. Results showed that the LC50 obtained were 102, and 154 spores/ml after treatingS. oryzae with different concentrations of B. bassiana and M. anisopliae, under laboratoryconditions; respectively. However, when S. oryzae treated with different concentrations ofB. thuringiensis the LC50 was 266Ug/ml. The accumulative mortality percentage was graduallyincreased by increasing the period of exposure to foam treated with different extracts. N. sativaoil had the highest accumulative mortality (78.15%), followed by T. distichum (50.17%) andB. carterii (30.19%). N. sativa oil had the highest repellant activity against S. oryzae reaching to61%. The reduction of the eggs laid per female was scored 95.3% eggs/ female after treatmentswith N. sativa oil. Under store conditions the percentages of infestation were significantlydecreased to 7, 10 and 17% after treating the stock sacs with B. thuringiensis, B. bassiana andM. anisopliae respectively compared to 98% in the stock sacs control. When the stock sacstreated with different oils, the infestations percentages were 45, 55 and 37% after treating withT. distichum, B. carterii and N. sativa; respectively. The gunny sacs paper followed bypolypropylene sacs provide more protection against S. oryzae.

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