Journal of Biopesticide

Journal of Biopesticide

2010, Vol. 3, Issue1

INVESTIGATIONS ON THE ENHANCING EFFICACY OF GRANULOVIRUS ON NUCLEOPOLYHEDROVIRUS OF HELICOVERPA ARMIGERA (HüBNER)


AUTHOR(S)
S. Jeyarani* and P. Karuppuchamy

ABSTRACT

The implementation of microbial control of insect pests especially with nucleopolyhedroviruses (NPVs) is less popular among the farmers owing to its slow action and reduced efficacy against grown up larvae. The infectivity of NPV against grown up larvae were reported to be enhanced by the presence of a viral enhancing factor (VEF) in granuloviruses (GV). Hence, investigations were carried out to find out the effect of Helicoverpa armigera Granulovirus (HaGV) on the nucleopolyhedrovirus of H. armigera (HaNPV) against second, third, fourth and fifth instar larvae. Results of the studies revealed that treatment of HaNPV, HaGV applied at LC50 doses alone or a combination of HaNPV (LC50) + HaGV (LC25) significantly caused higher mortalities due to polyhedrosis or polyhedrosis mixed with granulosis than other individual treatments tested at LC25, LC50 or their combinations. Data on the LT50 values against different instars indicated that combination of HaNPV + HaGV and HaGV alone at different doses resulted in lowered mortality and extension in survivorship time. Only in HaNPV treated at LC50 doses, the LT50 was found to be significantly the shortest recording 99.52, 100.31, 102.92 and 104.46 h against second, third, fourth and fifth instar larvae respectively. It was found that the efficacy of HaNPV was not enhanced by the HaGV and the decrease in the infectivity of HaNPV by HaGV might be due to out competing nature of HaGV for tissue sites or it might possess a viral factor such as a protein or peptide, for inhibiting viral replication. The efficacy of HaNPV was also not enhanced by the heat inactivated HaGV.


DOI
https://doi.org/10.57182/jbiopestic.3.1.172-176

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