Phototoxicity of Ultraviolet‐A against the Whitefly <i>Bemisia tabaci</i> and Its Compatibility with an Entomopathogenic Fungus and Whitefly Parasitoid

Abstract

Ultraviolet (UV) radiation significantly affects insect life and, as a result, has been widely used to control different invertebrate pests. The current results demonstrate that when <i>Bemisia tabaci</i> first instar nymphs are exposed to UV-A light for 12, 24, 48, and 72 h, their developmental and biological parameters are negatively affected by UV-A exposure; the effect increased with an increase in exposure time. We hypothesized that UV-A light is compatible with other biological control agents. Results showed that when the entomopathogenic fungus <i>Cordyceps fumosorosea</i> was applied to third instar nymphs of <i>B. tabaci</i> previously exposed to UV-A light, the LC₅₀ was 3.4% lower after 72 h of exposure to UV-A light compared to the control. However, when the fungus was exposed to UV-A light, its virulence decreased with an increase in UV-A exposure time. The parasitism rate of <i>Encarsia formosa</i> against 24 h UV-A-exposed third instar nymphs of <i>B. tabaci</i> increased while the adult emergence from parasitized nymphs was not affected after UV-A light exposure. Parasitism rate was significantly reduced however following <i>E. formosa</i> exposure to UV-A light; but again, adult emergence was not affected from parasitized nymphs. The percentage mortality of <i>E. formosa</i> increased with increasing exposure time to UV-A light. The enzyme activity of SOD, CAT, GST, and AChE and the energy reserve contents were negatively affected due to UV-A exposure. Collectively, this study has demonstrated that UV-A light significantly suppresses the immune system of <i>B. tabaci</i> and that UV-A light is compatible with other biological control agents if it is applied separately from the biological agent.