Phototoxicity of Ultraviolet‐A against the Whitefly Bemisia tabaci 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 Bemisia tabaci 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 Cordyceps fumosorosea was applied to third instar nymphs of B. tabaci 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 Encarsia formosa against 24 h UV-A-exposed third instar nymphs of B. tabaci increased while the adult emergence from parasitized nymphs was not affected after UV-A light exposure. Parasitism rate was significantly reduced however following E. formosa exposure to UV-A light; but again, adult emergence was not affected from parasitized nymphs. The percentage mortality of E. formosa 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 B. tabaci and that UV-A light is compatible with other biological control agents if it is applied separately from the biological agent.

Physiological and Molecular Response Modifications by Ultraviolet-C Radiation in Plutella xylostella and Its Compatibility with Cordyceps fumosorosea

“…The current study reported that exposure to UV-C radiation reduces the immunity of P. xylostella, which increase the effectiveness of C. fumosorosea . Khan et al [ 7 ] also reported that if Bemisia tabaci was exposed to UV-A before application of C. fumosorosea , the LC 50 decreases with an increase in exposure time, which implies that the B. tabaci become less and less immune against fungal infection due to UV-A exposure.…”

“…Most moths can tolerate UV irradiation; however, blacklight, a synthetic form of UV-light, has been extensively used to control nocturnal moths [ 3 , 4 ]. Previous studies reported a direct effect of UV light on insect behavior [ 5 ], development, biology, and physiology [ 6 , 7 ], and biochemistry [ 8 ], but there is no study available reporting direct mortality of moths caused by UV light.…”

Whitefly (Bemisia tabaci) Management (WFM) Strategies for Sustainable Agriculture: A Review

“…Natural enemies (predators, parasitoids, and entomophagous fungi) of B. tabaci have been thoroughly investigated and reviewed [104,105,220,221]. Over the last 20 years, enormous studies have proven the efficacy of parasitoids, entomopathogenic organisms, and predators in managing destructive insect pests including whiteflies on different agricultural plants [13,[222][223][224].…”

Imperfect match between radiation exposure times required for conidial viability loss and infective capacity reduction attenuate UV‐B impact on Beauveria bassiana

“…6,16,17 However, regarding the latter, numerous environmental stresses such as ozone depletion, increased UV radiation, biodiversity destruction, and temperature may impact EPF normal development in the field, whether the EPF have been applied as part of IPM plans or they are naturally present in these habitats. 18,19 One of the most harmful environmental factors affecting the depletion of EPF propagules is the sunlight fraction UV-B radiation (⊗ of 280-315 nm), which could directly affect the presence and persistence of EPF conidia in epigeal habitats. 7,20 It is welldocumented that UV-B radiation acts directly on DNA, RNA, and intracellular macromolecules (proteins, ribosomes, and biomembranes), and the development of compounds such as the reactive oxygen species (ROS) resulting in genetic modifications, cell toxicity, and signal pathway modification.…”