Field study to evaluate the joint action of certain insecticides, IGR's and baculoviruses against Spodoptera littoralis (Bosid.)
AA El-Helaly, HM El – bendary
As a selective biological insecticide, spinosad has been widely used for the control of pests including Spodoptera littoralis. It was studied very well in the laboratory last decade but there is a lake in knowledge in both field evaluations, lethal and sublethal effects to obtain a complete analysis of spinosad impact. This study attempts to evaluate the lethal and sublethal effects of spinosad on this pest by recording and analyzing various toxicological and physiological parameters. The toxicity of spinosad against S. littoralis was determined under Egyptian field conditions on Tomato plants in Fayoum Governorate in the period extended from June to July of 2014 conditions by oral exposure of late second-instar larvae to the compounds. The LC50 values of spinosad to S. littoralis tested at 24, 48, 72, 96,120, 144 and 168 h after treatment were 37.580, 19.050, 9.028, 7.019, 5.0182, 4.0181 and 2.0109 mg x kg(-1), respectively. Spinosad at sublethal concentrations significantly extended the developmental period of survivor larvae, and reduced larval wet weight. These doses were significantly reduced when Spinosad tested in combination with SpLiNPV trend at 1x 103 PIB's /ml to reach 17.3583, 8.5878. 4.1247, 2.1474, 1.2204, 0.1241 and 0.0147 mg x kg (-1) the same trend was obtained when Flufenoxuron was determined. However these data were compared with the recommended pesticide Diazinon. Some biological aspects were investigated and it was found that the effect of combination of Flufenoxuron with the NPV was the best in the field application followed by Spinosad in combination with the NPV virus. Also, the tested insecticides at LC50 concentration reduced food consumption, larval growth rate, efficiency of converting ingested and digested food into body tissue. This work concluded that combination of both bio-rational pesticides Flufenoxuron and Spinosad with virus is recommended in field.