Ahmed, F. S., W. S. Helmy, H. S. El-Din, and Y. A. Naggar, Chronic in-hive exposure to a field-relevant concentration of Closer™ SC (24% sulfoxaflor) insecticide altered immunological and physiological markers of honey bee foragers (Apis mellifera), , vol. 54, issue 1, pp. 4, 2023. AbstractWebsite

Sulfoxaflor (SULF), a well-known alternative for the banned neonicotinoids, is not environmentally persistent, yet numerous studies using field-realistic levels have demonstrated its detrimental impact on honey bee colonies. Despite this, even just a limited number of studies have addressed its residue-level effects on the physiological and immunological biomarkers of foraging honey bees in semi-field conditions. In the present study, we determined the LT50 of sulfoxaflor (Closer™ 24% SC) on forager bees in the laboratory at concentrations that were 12 to 300,000-fold lower than the field-recommended concentration. Following that, we exposed bee colonies in a semi-field in-hive experiment for 21 days to a concentration that is 600,000-fold lower than the field-recommended concentration to assess potential effects on the physiological state of honey bee foragers. To do that, a total of six colonies were treated with Closer™ (0.3 µg a.i./L) or control treatment, and the activities of acetylcholinesterase (AChE), glucose oxidase (GOX), and carboxylesterase (CaEs) in head tissues and invertase (IV), alkaline phosphatase (ALP), and glutathione-S-transferase (GST) in the midgut tissues of forager bees were assessed at 5-, 10-, 15-, and 20-day post-exposure. The LT50 results for the least and greatest concentrations of Closer™ were 0.37 and 74.3 h, respectively. Furthermore, all measured physiological and immunological biomarkers were negatively impacted in the chronic exposure to 0.3 µg a.i./L concentration of Closer™. This data demonstrated the importance of reviewing the risk assessment of various sulfoxaflor formulations on bees and rephrasing the legislation that governs how beekeepers deal with sulfoxaflor-sprayed fields.

Ahmed, F. S., Y. S. Helmy, and W. S. Helmy, Toxicity and biochemical impact of methoxyfenozide/spinetoram mixture on susceptible and methoxyfenozide-selected strains of Spodoptera littoralis (Lepidoptera: Noctuidae), , vol. 12, issue 1, pp. 6974, 2022. AbstractWebsite

Methoxyfenozide (M) is one of the selective insecticides used in integrated pest management (IPM) programs for lepidopteran pests. However, recent studies reported a development of M-resistance, which prompted us to look for alternatives. Here, we investigate the potency of a mixture of M with spinetoram (Sp) on M-resistant insects. In the laboratory, a selection pressure with M has carried out on Spodoptera littoralis (Lepidoptera: Noctuidae) strains. A dipping technique was used to evaluate the toxicity of a sublethal concentration of M and Sp. on S. littoralis larvae, and the same concentrations were used to assess the toxic impact of their combination on susceptible (SUS) and M-selected (MS) strains. The toxicity of M/Sp mixtures was computed using a combination index equation, and a potentiation effect was observed in the two tested strains. Synergism tests revealed that piperonyl butoxide had considerable synergistic effects on M toxicity in the MS strain. The results revealed that the M/Sp mixture's negative effect on both monooxygenases and esterases is most likely the cause of its potentiation effect on the SUS and MS strains. It was concluded that M/Sp mixtures are effective against M-resistant S. littoralis strains, so these can be used in IPM programs.

El-Din, H. S., W. S. Helmy, Y. A. Naggar, and F. S. Ahmed, Chronic exposure to a field-realistic concentration of Closer® SC (24% sulfoxaflor) insecticide impacted the growth and foraging activity of honey bee colonies, , vol. 53, issue 2, pp. 22, 2022. AbstractWebsite

The effects of sulfoxaflor on various pollinators have long been debated. However, there have been few in-hive studies on sulfoximines, and the effects on honey bee colony growth and foraging activity are unknown. Here, we calculated the LC50 of Closer® 24% suspension concentrate (SC) using honey bee foragers then assessed the impacts of chronic exposure of honey bees to a lesser concentration of Closer® in a semi-field in-hive experiment. To do that, we used a worst-case exposure scenario and fed bees for 21 days with a sublethal and field-relevant concentration of sulfoxaflor (0.3 ppb) which represents the calculated LC5 value of Closer®. A total of six colonies was assigned to the pesticide or control treatment. Then, we evaluated the colony development and activity as well as the weight and foraging activity of individual foraging bees. We also revealed that sublethal Closer® exposure impacted honey bee colony growth and activity by reducing bee bread, honey, and brood production, as well as weight and foraging performance of individual bees when colonies were kept under field conditions. Given the findings of this study, as well as comparable findings reported on spray application of Closer® using standard application practices in semi-field conditions, sulfoxaflor’s potential harm to pollinators at realistic levels merits additional investigation particularly in combination with other stressors to better understand how novel insecticides influence pollinators and pollination services.

Swelam, E. S., H. R. Abdel-Rahman, A. - T. H. Mossa, and F. S. Ahmed, Influence of temperature on the toxicity of fipronil to Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), , vol. 39, pp. 102277, 2022. AbstractWebsite

An effective pest management necessitates the use of insecticides throughout the entire season under a wide range of temperatures. Fipronil is a broad-spectrum insecticide that can be used indoors and outdoors throughout the year to control various pests. Using a leaf-dipping bioassay technique, the effect of different temperatures (range, 15°C–35 °C) on the toxicity of fipronil against the fourth instar larvae of Spodoptera littoralis (Boisd.) was assessed. The temperature coefficient was calculated, and the toxicity of fipronil showed a positive correlation with temperature within the range of 20 °C−25 °C (3.78-fold). Meanwhile, fipronil exhibited a negative correlation over the 15 °C−20 °C temperature range (−6.55-fold). The most intriguing finding was that when the temperature rose from 20 °C to 35 °C, the toxic effect of fipronil improved by 14.5-fold. The fourth instar larvae were treated with an estimated LC50 value of each fipronil thermal condition (15 °C, 20 °C, 25 °C, and 35 °C), and the protein hemolymphs of the treated larvae were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The highly effective tested treatment, the 35 °C fipronil-maintained group (LC50 of 2.79 ppm), and its control group displayed the lowest number of protein bands (seven bands). The effect of fipronil under the different thermal conditions on amylase, total lipids, aspartate aminotransferase, alanine aminotransferase, acid phosphatase, and alkaline phosphatase of S. littoralis larvae was also evaluated. Treatments showed varied effects on the biochemical parameters measured. This study emphasizes the benefits of using fipronil under specific thermal conditions to achieve the highest efficiency in combating target pests with the fewest concentrations.

Othman, K. S. A., E. S. Swelam, and F. S. Ahmed, "A Laboratory Study of the Toxicity of Indoxacarb Mixtures against Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)", African EntomologyAfrican Entomology, vol. 28, issue 2, pp. 290 - 299, 2020/9/1. AbstractWebsite
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Fouad, E. A., F. S. Ahmed, and M. A. M. Moustafa, "Monitoring and biochemical impact of insecticides resistance on field populations of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) in Egypt", Polish Journal of Entomology, vol. 91, issue 3, pp. 109-118, 2022.