| Abstrakt: |
The tropical armyworm, Spodoptera lituraFabricius (Noctuidae; Lepidoptera), is among the most harmful pests causing economic loss in the quality and production of a variety of crops, particularly cotton. Entomopathogens play an important role in insect pest management. The nuclear polyhedrosis virus (NPV) isolate of S. litura(V-SpltNPV) was isolated from infected larvae in a cotton crop, and viral occlusion bodies were confirmed, using an inverted microscope. The pathogenicity of V-SpltNPV against 2nd, 3rd, and 4th larval instars of S. liturawas evaluated at various concentrations (1 × 104to 1 × 108OBs/ml). Mortality rate was high (37.65–96.82%) in early instar larvae against tested concentrations. LC50and LT50values increased with increasing larval age. There was 689,865 times increase in LC50value (1.35 × 102OBs/ml) for 2nd instar larvae to LC50value (6.90 × 105OBs/ml) for 4th instar larvae. LT50values enhanced from 4.99 days for 2nd instar larvae to 7.49 days for 4th instar larvae, due to a decrease in efficacy of NPVs with the increasing age of larvae. In a greenhouse experiment, a combined application of spinosad with V-SpltNPV (1 × 108OBs/ml) caused (100%) mortality of 2nd instar larvae. A single application of V-SpltNPV (1 × 108OBs/ml) resulted to mean mortality (52.63%) of tested larvae. The native isolate V-SpltNPV seems to have a potential to be used in integrated manner with other IPM tactics to significantly reduce the use of toxic chemical pesticides. |
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