Host Range and Pathogenicity Potential of Helicoverpa armigera Nucleopolyhedrovirus (HaNPV) to Lepidopterous Pests of Cotton

Abstract

Farmers rely on chemical control for managing insect pests which cause various human and environmental health hazards. So, biopesticides like Nucleopolyhedrovirus (NPVs) can be a suitable alternative due to their less toxic effects on non-target organisms and environment. As a matter of fact, NPVs have been proven very effective against lepidopteran larvae. However, defining the host range of NPV was required according to the ecological conditions of Pakistan. So, this study was planned in which NPV isolated from Helicoverpa armigera, HaNPV, was used to infect H. armigera, Spodoptera litura, S. exigua, Pectinophora gossypiella and Trichoplusia ni under controlled conditions (temperature = 25 ± 2 °C; RH = 60 ± 5%). Higher mortality was observed in H. armigera among all the tested hosts. Additionally, mortality of all the other tested species showed no significant difference as compared to their untreated control. Similarly, a higher peak was achieved in H. armigera after two days of infection. Due to the multiplication of virions inside the host body, host tissues are destroyed. Many factors like larval body size, temperature and environmental conditions affect the rate of response and pathogenicity. Thus the pathogenicity varies with time of infection. Decrease in infection and mortality can be attributed to resistance and increase in the size of larvae with the passage of time. Non significant mortality in non-hosts species by HaNPV suggests its highly specific nature. Thus, it can be successful highly specific ecofriendly management tool for H. armigera. However, in extreme environmental conditions, NPV should be used with sunblock.

Keywords

• Cotton
• Lepidopteran larvae
• Mortality
• NPV infection
• morbidity