DefinePK

Abstract

Background and Objective Resistance to pesticides is probably the biggest challenge facing pesticides researches today. The objective of this study was to test some of their combination against Spodoptera littoralis Boisduval to help developing control program in the future and increase their efficiency on S. littoralis that could inhibit or delay the emergence of resistant strains. Materials and Methods Three methods of the substances determined the effect of joint action against S. littoralis larvae and the impact of these combinations on some biological characters and fecundity were studied. Results Beni-suef strain showed tolerance ratios of 129.57 and 58.67 to chlorpyrifos and fenpropathrin, respectively. On the other hand, the El-monofia strain showed tolerance ratios of 89.86 and 44.08 to the same insecticides, respectively. The two F-strains show slight tolerance rates to spinosad. The combination of spinosad and fenpropathrin results in a synergistic effect, while chlorpyrifos results in additive or antagonistic effect. Conclusion All the tested combinations showed significantly reduce mean larval and pupal weight, pupation , adult emergence , fecundity and fertility compared with the control. While, prolonged larval duration and some of the mixtures showed sterility effect.