Timely inoculation of Helicoverpa armigera nucleopolyhedrovirus improves its efficiency in combination with benzoylphenylurea compounds
2022
Mehrvar, Ali | Saber, Moosa
Helicoverpa armigera nucleopolyhedrovirus (HearNPV) is highly virulent against cotton bollworm, and its combination with peritrophic membrane affecting chemicals, especially benzoylphenylurea compounds, can increase the relative speed of kill, leading to early and timely pest control. The biological activity of three HearNPV isolates (IR03, IR18, and IR20) was primarily evaluated on the second instar larvae of H. armigera. The highly virulent isolate (IR18, LC₅₀: 8.43 × 10³ OB/ml) and four benzoylphenylurea compounds (diflubenzuron, teflubenzuron, flufenoxuron, and lufenuron) were assessed on the pest larvae according to four per orally diet inoculation schedules. The highest mortality values were obtained when the virus was inoculated on the second (schedule 1) and third (schedule 2) days after flufenoxuron contamination with 98.67% and 97.30%, respectively, followed by teflubenzuron. All the benzoylphenylureas showed the highest mortalities using these two schedules. Flufenoxuron had a higher relative efficiency percent than the other compounds in all the schedules. The second schedule yielded the lowest LT₅₀ value using flufenoxuron with the highest relative speed of kill (38.40%), followed by the first schedule (30.02%). The second schedule can be relatively considered the most appropriate method for the combined use of benzoylphenylurea and HearNPV.
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