Fatma S H E R I F Ahmed | Cairo University (original) (raw)
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Papers by Fatma S H E R I F Ahmed
Scientific Reports
Methoxyfenozide (M) is one of the selective insecticides used in integrated pest management (IPM)... more 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...
Toxicity and biochemical impact of methoxyfenozide/ spinetoram mixture on susceptible and methoxyfenozide‑selected strains of Spodoptera littoralis (Lepidoptera: Noctuidae), 2022
Methoxyfenozide (M) is one of the selective insecticides used in integrated pest management (IPM)... more 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.
Monitoring and biochemical impact of insecticides resistance on field populations of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) in Egypt, 2022
Cotton leafworm, Spodoptera littoralis (Boisd.) is a key pest affecting many field crops and vege... more Cotton leafworm, Spodoptera littoralis (Boisd.) is a key pest affecting many field crops and vegetables in Egypt. Therefore, in the current study, the susceptibility of the 2 nd instar larvae of S. littoralis laboratory strain to eight insecticides was investigated and the insecticide resistance levels of two field populations were monitored. The two populations were collected from two governorates in Egypt, namely El-Monufia (MS) and El-Fayoum (FS). Resistance monitoring showed that the field population from El-Fayoum was highly resistant to chlorantraniliprole, emamectin benzoate (EMB), spinotram, and spinosad. However, the El-Monufia field population only exhibited high resistance to chlorantraniliprole and spinosad. The relative toxicity showed that the laboratory strain is highly sensitive to EMB (LC50= 0.001 ppm) followed by spinotram (LC50= 0.006 ppm), chlorantraniliprole (LC50= 0.008 ppm), spinosad (LC50= 0.008 ppm), and indoxacarb (LC50= 0.021 ppm), while chlorfenapyr, fipronil, and alpha-cypermethrin exhibited low toxicity to the laboratory strain of S. littoralis. Moreover, the biochemical determinations of detoxification enzymes revealed that carboxylesterase (α, and β-esterase), and AChE activity were significantly increased in the FS population. Thus, Glutathione S-Transferase (GST) showed significant increase in the two populations.
Influence of temperature on the toxicity of fipronil to Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), 2022
An effective pest management necessitates the use of insecticides throughout the entire season un... more 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 LC 50 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 (LC 50 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.
Chronic exposure to a field‑realistic concentration of Closer ® SC (24% sulfoxaflor) insecticide impacted the growth and foraging activity of honey bee colonies, 2022
The effects of sulfoxaflor on various pollinators have long been debated. However, there have bee... more 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 LC 50 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 LC 5 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.
The effects of sulfoxaflor on various pollinators have long been debated. However, there have bee... more 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 LC 50 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 LC 5 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.
A laboratory study of the toxicity of indoxacarb mixtures against Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), 2020
This study, using the combination index (CI) isobologram equation, evaluated the efficacy of indo... more This study, using the combination index (CI) isobologram equation, evaluated the efficacy of indoxacarb in binary mixtures with lufenuron, methoxyfenozide, chlorpyrifos, profenofos, and lambda-cyhalothrin against second instar larvae of Spodoptera littoralis (Boisd.). The efficacy of individual insecticides and their binary mixtures were evaluated using a leaf dipping technique. Percentage mortality was calculated after 72 h of treatment. The results indicated that indoxacarb was highly effective against second instar larvae of S. littoralis where the LC50 was 0.041 mg/l. Lambda-cyhalothrin was the least effective insecticide. Among the five binary mixtures tested, the indoxacarb/chlorpyrifos mixture was the most effective against second instar larvae where the calculated CI values for this mixture were 0.17, 0.12, and 0.21 at LC10, LC25, and LC50, respectively. Latent effects of binary mixtures on some biological parameters of S. littoralis were also evaluated where some of the tested mixtures showed a significant effect on the biological parameters measured.
Scientific Reports
Methoxyfenozide (M) is one of the selective insecticides used in integrated pest management (IPM)... more 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...
Toxicity and biochemical impact of methoxyfenozide/ spinetoram mixture on susceptible and methoxyfenozide‑selected strains of Spodoptera littoralis (Lepidoptera: Noctuidae), 2022
Methoxyfenozide (M) is one of the selective insecticides used in integrated pest management (IPM)... more 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.
Monitoring and biochemical impact of insecticides resistance on field populations of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) in Egypt, 2022
Cotton leafworm, Spodoptera littoralis (Boisd.) is a key pest affecting many field crops and vege... more Cotton leafworm, Spodoptera littoralis (Boisd.) is a key pest affecting many field crops and vegetables in Egypt. Therefore, in the current study, the susceptibility of the 2 nd instar larvae of S. littoralis laboratory strain to eight insecticides was investigated and the insecticide resistance levels of two field populations were monitored. The two populations were collected from two governorates in Egypt, namely El-Monufia (MS) and El-Fayoum (FS). Resistance monitoring showed that the field population from El-Fayoum was highly resistant to chlorantraniliprole, emamectin benzoate (EMB), spinotram, and spinosad. However, the El-Monufia field population only exhibited high resistance to chlorantraniliprole and spinosad. The relative toxicity showed that the laboratory strain is highly sensitive to EMB (LC50= 0.001 ppm) followed by spinotram (LC50= 0.006 ppm), chlorantraniliprole (LC50= 0.008 ppm), spinosad (LC50= 0.008 ppm), and indoxacarb (LC50= 0.021 ppm), while chlorfenapyr, fipronil, and alpha-cypermethrin exhibited low toxicity to the laboratory strain of S. littoralis. Moreover, the biochemical determinations of detoxification enzymes revealed that carboxylesterase (α, and β-esterase), and AChE activity were significantly increased in the FS population. Thus, Glutathione S-Transferase (GST) showed significant increase in the two populations.
Influence of temperature on the toxicity of fipronil to Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), 2022
An effective pest management necessitates the use of insecticides throughout the entire season un... more 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 LC 50 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 (LC 50 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.
Chronic exposure to a field‑realistic concentration of Closer ® SC (24% sulfoxaflor) insecticide impacted the growth and foraging activity of honey bee colonies, 2022
The effects of sulfoxaflor on various pollinators have long been debated. However, there have bee... more 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 LC 50 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 LC 5 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.
The effects of sulfoxaflor on various pollinators have long been debated. However, there have bee... more 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 LC 50 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 LC 5 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.
A laboratory study of the toxicity of indoxacarb mixtures against Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), 2020
This study, using the combination index (CI) isobologram equation, evaluated the efficacy of indo... more This study, using the combination index (CI) isobologram equation, evaluated the efficacy of indoxacarb in binary mixtures with lufenuron, methoxyfenozide, chlorpyrifos, profenofos, and lambda-cyhalothrin against second instar larvae of Spodoptera littoralis (Boisd.). The efficacy of individual insecticides and their binary mixtures were evaluated using a leaf dipping technique. Percentage mortality was calculated after 72 h of treatment. The results indicated that indoxacarb was highly effective against second instar larvae of S. littoralis where the LC50 was 0.041 mg/l. Lambda-cyhalothrin was the least effective insecticide. Among the five binary mixtures tested, the indoxacarb/chlorpyrifos mixture was the most effective against second instar larvae where the calculated CI values for this mixture were 0.17, 0.12, and 0.21 at LC10, LC25, and LC50, respectively. Latent effects of binary mixtures on some biological parameters of S. littoralis were also evaluated where some of the tested mixtures showed a significant effect on the biological parameters measured.