Abstract
The impact of several insecticides has been studied on a Spodoptera littoralis cell line and their effects on the replication of S. littoralis nucleopolyhedrovirus (Sl NPV). Four chemical insecticides, Chloropyrifos Fenitrothion, Cypermethrin and Carbaryl which belong to three different groups of pesticide, organophosphorus, pyrethroid, and carbamate, respectively, were used. The results demonstrate an increase of more than 25% in the multiplication of Sl cells when treated with Chloropyrifos dilutions compared with untreated cells. The most destructive pesticide was Cypermethrin, which caused 84% inhibition of cell development (0.4×106 cell/ml) at a concentration of 10-3 μg/ml in preliminary tests. In the presence of both Sl NPV and sublethal doses of these insecticides, the TCID50 values revealed that the Cypermethrin (10-8 μg/ml) was the most toxic (ID50 was 6.48×105/ml) whereas Chloropyrifos was the least toxic (ID50 9.29×1012/ml) at a concentration of 0.731 μg/ml. The PFU values confirm the results that the same concentration of Chloropyrifos (0.73lμg/ml) was the least toxic (PFU 6.41×1013/ml) and Cypermethrin was the most toxic (4.47×106/ml PFU) for the other concentrations as well as the different insecticides the PFU values ranged between 2.8×108 for Chloropyrifos at a concentration of 10-3 μg/ml and 9.76×1012 for Carbaryl at 10-5 μg/ml. A comparison with the results obtained using Sl NPV without chemicals (the PFU 3.5×109/ml) indicates an increase in the production of virus and titer, and a synergistic effect of the chemicals. These results confirm the effect of these insecticides in vivo. As the Cypermethrin may have a potent effect on the exchange of ions through the cell membrane in vitro and in vivo, it could be partially explain the impact of the insecticides and their mode of action.
