Department of Entomology, Punjab Agricultural University, Ludhiana-141 004, Punjab (India).
Three native isolates of NPV of Heliothis armigera Hubner from different areas of Punjab (India) were evaluated in the laboratory along with two commercially available HaNPV isolates from other parts of the country. Five-day old (2nd instar) larvae of H. armigera were reared singly on cotton leaves treated with different concentrations of NPV by leaf-dip method. The LT50 values calculated from the mortality data revealed wide differences in the activity of these five isolates. The order of activity of the isolates was:PAU > Karaiwala > Mudki > Bangalore > Godhra. Nine days after feeding on NPV-treated food showed that the PAU isolate with an LCSo value of 0.3593 LEA was the most effective against H. armigera. It was followed by the Karahuala (0.5091 LE/1) and Mudki (0.5134 LE/1) isolates with overlapping fiducial limits. The Bangalore (1.1214 LE/1) and Godhra (1.2515 LE/1) isoaltes were significantly inferior to the three isolates from Punjab. It is suggested that restriction endonuclease analysis would further confirm the presence of genotypic variants in different geogrpahic isolates of HaNPV.
