Acaricidal efficacy of ultraviolet-C irradiation of Tetranychus urticae adults and eggs using a pulsed krypton fluoride excimer laser

Abstract

Background Pulsed ultraviolet (UV)-C light sources, such as excimer lasers, are used in emerging non-thermal food-decontamination methods and also have high potential for use in a wide range of microbial decontamination applications. The acaricidal effect of an experimental UV-C irradiation device was assessed using female adults and eggs of a model organism, the two-spotted spider mite Tetranychus urticae. Methods UV-C light was generated by a pulsed krypton fluoride excimer laser operating at 248-nm emission wavelength. The pulse energy and pulse repetition rate were 5 mJ and up to 100 Hz, respectively. The distance from the light source to the target was 150 mm; the target surface area was 2.16 cm2. The exposure time for the mites and fresh eggs varied from 1 to 4 min at 5–300 mW, which corresponded to UV doses of 5–80 kJ/m2. Post-irradiation acaricidal effects (mite mortality) were assessed immediately and also measured at 24 h. The effects of UV-C irradiation on the hatchability of eggs were observed daily for up to 12 days post-irradiation. Results The mortality of mites at 5 and 40 kJ/m2 was 26% and 92%, respectively. Mite mortality reached 98% at 80 kJ/m2. The effect of exposure duration on mortality was minimal. The effect of irradiation on egg hatchability was even more significant than that on adult mite mortality, i.e. about 100% egg mortality at an accumulated dose of as little as 5 kJ/m2 for each exposure time. Conclusions A high rate of mite mortality and lethal egg damage were observed after less than 1 min of exposure to 5 mJ UV-C pulsed irradiation at 60 Hz. Pending further developments (such as beam steering, beam shaping and miniaturisation) and feasibility studies (such as testing with mites in real-life situations), the reported results and characteristics of the UV-C generator (modulation of energy output and adaptability to varying spot sizes) open up the use of this technology for a vast field of acaricidal applications that require long-range radiation. Graphical Abstract

Sustainable laser technology for the control of organisms and microorganisms in agri-food systems: a review

“…Pulsed light technology involves the application of intense light in the form of short, high-intensity pulses aimed at a target of interest, with a high degree of penetration, maximum power emission capability and at a maximum power distribution during the short pulses. The pulsed UV light effectively inactivates micro-organisms and organisms such as bacteria, yeasts, fungi, viruses, and also insects (Gala et al, 2021). However, it should be remembered that there are dangers associated with UV radiation, its misuse is not compatible with human health, this depends on the lamps and wavelengths used, for example, UV-C should not be viewed with the naked eye, adequate ventilation is vital as this wavelength sometimes generates ozone.…”

“…In addition to their application in food processing and in the conditioning of seeds, seedlings and plants, laser light sources could be applied to improve sanitary quality and help to reduce the use of agrochemicals during the development of crops in the face of different problems of the agri-food system all the way up to the level of home consumption, in circumstances where agrochemicals or chemicals that harm the environment and human beings are currently being used. This physical technology has advantages over the chemical inactivation of microbi-cidal procedures and is considered to be environmentally friendly as it does not leave potentially toxic residues in the environment and has the potential to extend the shelf life of perishable foods (Govindaraj et al, 2017;Gala et al, 2021;Chavan et al, 2023;Gonca et al, 2023).…”