Effect of Two Azadirachtin Formulations against Adults of Sitophilus oryzae and Tribolium confusum on Different Grain Commodities

• Published in: Journal of food protection 2007-07, Vol.70 (7), p.1627-1632
• Main Authors: Kavallieratos, N.G, Athanassiou, C.G, Saitanis, C.J, Kontodimas, D.C, Roussos, A.N, Tsoutsa, M.S, Anastassopoulou, U.A
• Format: Article
• Language: English
• Subjects: adult insects; ambient temperature; Animals; Azadirachta indica; azadirachtin; Biological and medical sciences; Cereal and baking product industries; corn; dosage; dose response; Dose-Response Relationship, Drug; environmental factors; essential oils; food grains; Food industries; Food microbiology; Food Preservation - methods; Fundamental and applied biological sciences. Psychology; Humidity; insecticidal properties; Insecticides - pharmacology; Limonins - pharmacology; plant extracts; relative humidity; Sitophilus oryzae; storage insects; stored product protection; Temperature; Time Factors; Tribolium - drug effects; Tribolium - growth & development; Tribolium confusum; Triticum - microbiology; Triticum aestivum; Weevils - drug effects; Weevils - growth & development; wheat; Zea mays; Zea mays - microbiology
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028x-70.7.1627

The insecticidal effect of two azadirachtin-based insecticides, NeemAzal-T/S and Oikos 32 EC, was examined against adults of the grain beetles Sitophilus oryzae and Tribolium confusum on wheat and maize under different temperature and humidity regimes. The insecticides were applied at three dosages, equivalent to 50, 100, and 200 mg of active ingredient per kg of grain. Adults of the above species were exposed to the treated grains at 20, 25, and 30 degrees C and two relative humidity levels (55 and 75%), and mortality was assessed after 14 days of exposure. All adults were then removed, and the treated substrate remained under the same conditions for 45 more days. After this period, the grains were checked for progeny production. In both species and both commodities, mortality increased with insecticide dosage. For many dosage-formulation combinations, mortality increased with temperature at 55% relative humidity but the reverse was observed at 75% relative humidity. Comparing the two formulations, NeemAzal-T/S was more effective than Oikos 32 EC at all the combinations tested. NeemAzal-T/S was more effective at high relative humidity, but the efficacy of Oikos 32 EC was not much affected by the relative humidity. Survival was high, even at the higher dosages, in some of the temperature-humidity combinations. Progeny production of S. oryzae in the treated grains was considerably higher than that of T. confusum. The results of the present study indicate that further dosage increases and longer exposure times are needed to obtain a complete (100%) adult mortality in all combinations tested. However, the feasibility of using higher azadirachtin dosages (>200 mg/kg grain) is questionable for cost reasons. Consequently, the use of these substances is not comparable to the use of traditional grain protectants, which are usually used at dosages of