Purpose: The Deoxyribonucleic Acid (DNA) Comet assay, being a quick, simple, sensitive, reliable and fairly inexpensive method for measuring DNA strand breaks, has been used to assess DNA damage caused by gamma radiation in developmental stages of maize weevil Sitophilus zeamais Motschulsky. Materials and methods: An analysis of DNA damage following gamma radiation (⁶⁰Cobalt) treatments at a dose of 0.5 and 1.0 kGy (Kilo Gray) has been carried out with cells obtained from the larvae, pupae and adults of S. zeamais. Results: Gamma radiation induced significant damage at DNA level in the experimental larvae, pupae and adults as manifested by increased strand breaks compared to intact cells from non-irradiated ones. Comet assay revealed that tail length and % tail DNA varied significantly for all developmental stages of S. zeamais. Conclusions: This study suggests that the comet assay would be a potentially useful tool for detecting DNA damage in insect pest control strategies due to its advantages in the requirement of small numbers of cells per sample and sensitivity in detecting low levels of DNA damage.

Research here explored the use of controlled atmospheres (CA) for managing arthropod pests that infest dry-cured hams. Experiments were conducted with low oxygen (O₂) achieved with low pressure under a vacuum, high carbon dioxide (CO₂), and ozone (O₃). Results showed that both low O₂ and high CO₂ levels required exposures up to 144 h to kill 100% of all stages of red-legged ham beetle, Necrobia rufipes (De Geer) (Coleoptera: Cleridae) and ham mite Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) at 23 °C. In addition, both low O₂ and high CO₂ had no significant mortality against the ham beetle and ham mites at short exposures ranging from 12 to 48 h. Ham beetles were more tolerant than ham mites to an atmosphere of 75.1% CO₂ and low pressure of 25 mm Hg, which imposed an atmosphere estimated at 0.9% O₂. Both low O₂ and high CO₂ trials indicated that the egg stages of both species were more tolerant than other stages tested, but N. rufipes eggs and pupae were more susceptible than larvae and adults to high concentration ozone treatments. The results indicate that O₃ has potential to control ham beetles and ham mites, particularly at ≈166 ppm in just a 24 h exposure period, but O₃ is known from other work to have poor penetration ability, thus it may be more difficult to apply effectively than low O₂ or high CO₂. would be. CA treatment for arthropod pests of dry-cured hams show promise as components of integrated pest management programs after methyl bromide is no longer available for use.

The soft-electron beam (low-energy electrons) and gamma-radiation sensitivities of phosphine-resistant (PHR) and -susceptible (PHS) strains of adults lesser grain borer Rhyzopertha dominica (F.) were studied, with particular reference to DNA damage assessed using single-cell electrophoresis (comet assay). Results showed that mortality in adult R. dominica varied significantly between both PHR and PHS strains. Adults of the PHR strain were found to be more tolerant toward soft-electron and gamma radiation than adults of the PHS strain. Studies on the longevity of strains showed that mean survival time and dose rate were highly correlated with both strains and treatments. Results also showed that adults of the PHR strain lived longer than adults of PHS strain for both treatments. Radiation sensitivity indices, however, decreased as radiation dose increased in both strains. Analysis of DNA damage, after 40- and 160-Gy gamma radiation, was carried out using cells obtained from both strains. Gamma-irradiated adults of both strains showed typical DNA fragmentation, compared with cells from nonirradiated adults, which showed more intact DNA. Investigations using the comet assay showed that tail length, moment, olive-tail moment, percentage of tail DNA, and percentage of DNA damage were all greater in the PHS strain compared with the PHR strain and the control insects. Results also showed that DNA damage remained at a constant level for up to 24 h after irradiation. The results have been discussed in relation to the observed strain differences in radiation sensitivity and resistance to phosphine.

The egg parasitoidTrichogramma evanescensWestwood is considered as an efficient biological control agent for managing several lepidopteran pests and it is widely distributed throughout the world. Mass rearing protocols of parasitoids that are currently in use in biocontrol programs require a meticulous quality control plan, in order to optimize their efficacy, but also their progeny production capacity. In this paper, the effect of different factors on the quality control in mass rearing ofT.evenescens, usingPlodia interpunctella(Hübner) andGalleria mellonellaL. as host species, were investigated. The impact of egg agewas significant in the rates of parasitism, for both host species tested. Significantly highest percent of parasitoid emergence was noticed in two day-old eggs for both host species, while one day-old eggs day exhibited the maximum emergence when both species were used togetherin the same trials. Age-dependent storage egg preservation at either 4 or 9°C significantly influenced the parasitism percentages on both species. The highest parasitism percentage was recorded in two day-oldG.mellonellaeggs that are kept for 15 days at 9°C while the lower in one day-oldP.interpunctellaeggs for 60 d storage. Moreover, the highest parasitoid mortality was recorded inT.evanescensreared either onP.interpunctellaorG.mellonellaat 20°C. Rearing of the parasitoid on a mixture of eggs of both host species resulted in higher parasitism, but not always in higher rates of parasitoid emergence. The results of the present work provide useful information that can be further utilized in rearing protocols ofT.evanescens.