Phytochemical Investigation of Three Cystoseira Species and Their Larvicidal Activity Supported with In Silico Studies.

Culex pipiens mosquitoes are transmitters of many viruses and are associated with the transmission of many diseases, such as filariasis and avian malaria, that have a high rate of mortality. The current study draws attention to the larvicidal efficacy of three methanolic algal extracts, Cystoseira myrica, C. trinodis, and C. tamariscifolia, against the third larval instar of Cx. pipiens. The UPLC-ESI-MS analysis of three methanol fractions of algal samples led to the tentative characterization of twelve compounds with different percentages among the three samples belonging to phenolics and terpenoids. Probit analysis was used to calculate the lethal concentrations (LC50 and LC90). The highest level of toxicity was attained after treatment with C. myrica extract using a lethal concentration 50 (LC50) of 105.06 ppm, followed by C. trinodis (135.08 ppm), and the lowest level of toxicity was achieved by C. tamariscifolia (138.71 ppm) after 24 h. The elevation of glutathione-S-transferase (GST) and reduction of acetylcholine esterase (AChE) enzymes confirm the larvicidal activity of the three algal extracts. When compared to untreated larvae, all evaluated extracts revealed a significant reduction in protein, lipid, and carbohydrate contents, verifying their larvicidal effectiveness. To further support the observed activity, an in silico study for the identified compounds was carried out on the two tested enzymes. Results showed that the identified compounds and the tested enzymes had excellent binding affinities for each other. Overall, the current work suggests that the three algal extractions are a prospective source for the development of innovative, environmentally friendly larvicides.

Characterization of Spodoptera littoralis (Lepidoptera: Noctuidae) resistance to indoxacarb: inheritance mode, realized heritability, and fitness costs.

Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) is a major economic pest attacking a variety of crops in Egypt and other Mediterranean countries. S. littoralis has developed resistance to both traditional and novel insecticides. The current study investigated S. littoralis resistance to indoxacarb regarding inheritance mode, realized heritability (h2), and fitness costs. An indoxacarb-resistant strain (Indoxa-SEL) was obtained by selecting a field strain with indoxacarb. Indoxa-SEL strain outperformed the susceptible one (Indoxa-S) by 29.77-fold after 16 consecutive generations of selection. Based on the LC50 values of the progenies of reciprocal crosses F1 (R♂ × S♀) and F1' (R♀ × S♂), S. littoralis resistance to indoxacarb was found to be autosomal and partially recessive. Chi-square tests for goodness-of-fit between observed and expected mortalities of self-bred F1 and resistant strain reciprocal crosses revealed that the resistance was controlled by multiple genes. The resistant strain had a relative fitness of 0.80, with significantly increased total preovipositional period of females, egg, larvae, pupae, preadult, adult, and total longevity period. The estimated realized heritability value in the Indoxa-SEL strain was 0.21. The current study will contribute to sustaining indoxacarb efficacy and designing effective resistance management programs against S. littoralis.

Target Enzymes of Origanum majorana and Rosmarinus officinalis Essential Oils in Black Cutworm (Agrotis ipsilon): In Vitro and In Silico Studies.

In this study, in vitro and in silico approaches were employed to assess the toxicity of marjoram (Origanum majorana) and rosemary (Rosmarinus officinalis) essential oils (EOs) to A. ipsilon larvae. The study determined the activities of ATPases in the larvae after treatment with the LC20 and LC70 of each EO. α-esterase and glutathione-S-transferase (GST) activities were also determined after treatment with LC10 and LC30 of each EO. Furthermore, molecular docking was employed to determine the binding affinity of terpinene-4-ol and α-pinene, the major constituents of O. majorana, and R. officinalis EOs, respectively, compared to the co-crystallized ligand of α-esterase, diethyl hydrogen phosphate (DPF). Toxicity assays revealed that O. majorana EO was more toxic than R. officinalis EO to the A. ipsilon larvae at 96 h post-treatment. However, the LC20 and LC70 of the latter significantly inhibited the activity of the Na+-K+ pump at almost all intervals. The same concentrations significantly inhibited the Mg2+/Ca2+-ATPase and Ca2+ pump at 96 h post-treatment. In contrast, O. majorana EO showed a variable effect on the Na+-K+ pump across different time intervals. On the other hand, LC10 and LC30 of both EOs showed varied effects on α-esterase and GST over time. Molecular docking revealed energy scores of -4.51 and -4.29 kcal/mol for terpinene-4-ol and α-pinene, respectively, compared to a score of -4.67 for PDF. Our study demonstrated the toxicity of the tested EOs to A. ipsilon, suggesting their potential efficacy as insecticides.

Towards Sustainable Pest Management: Toxicity, Biochemical Effects, and Molecular Docking Analysis of Ocimum basilicum (Lamiaceae) Essential Oil on Agrotis ipsilon and Spodoptera littoralis (Lepidoptera: Noctuidae).

Over the last decade, essential oils (EOs) have become potential ingredients for insecticide formulations due to their widespread availability and perceived safety. Therefore, this study aimed to evaluate the toxicity and biochemical efficacy of basil (Ocimum basilicum) (Lamiaceae) against two destructive pests Noctuidae, Agrotis ipsilon (Hufnagel) and Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). In addition, a molecular docking study was performed to gain insight into the binding pattern between glutathione S-transferase (GST) and linalool, the main component of EO. GC-MS analysis of O. basilicum EO revealed that linalool is the most abundant compound (29.34%). However, the toxicity tests showed no significant difference between the values of LC50 of O. basilicum EO to A. ipsilon and S. littoralis. On the other hand, the sublethal experiments indicated that treating the second instar larvae with LC15 or LC50 values of O. basilicum EO significantly prolonged the larval duration in both insects, compared to the control. Regarding the biochemical effect of O. basilicum EO, the treatments significantly impacted the activity of detoxification enzymes. A notable elevation in glutathione S-transferase (GST) activity was recorded in A. ipsilon larvae compared with a reduction in S. littoralis larvae. The molecular docking analysis revealed that linalool bonded with the amino acid serine (SER 9) of GST, indicating its binding affinity with the enzyme. The obtained results could offer valuable insights into the mode of action of O. basilicum and can encourage the adoption of sustainable pest control practices that incorporate essential oils.

Lethal and Sublethal Effects of Cyantraniliprole on the Biology and Metabolic Enzyme Activities of Two Lepidopteran Pests, Spodoptera littoralis and Agrotis ipsilon, and A Generalist Predator, Chrysoperla carnea (Neuroptera: Chrysopidae).

Cyantraniliprole is a novel anthranilic diamide insecticide registered for controlling chewing and sucking insect pests. Here, the lethal and sublethal effects of this insecticide on two destructive lepidopteran pests, Spodoptera littoralis Boisduval and Agrotis ipsilon Hufnagel, were evaluated. Because the effects of novel insecticides on beneficial and non-target arthropods must be considered, the impact of cyantraniliprole on a generalist biological control agent, Chrysoperla carnea [Stephens 1836], were also examined. Overall, our study revealed that cyantraniliprole was more toxic to A. ipsilon than to S. littoralis. Moreover, the LC15 and LC50 of the insecticide significantly prolonged the duration of the larval and pupal stages and induced enzymatic detoxification activity in both species. Treatment of the second-instar larvae of C. carnea with the recommended concentration of cyantraniliprole (0.75 mg/L) doubled the mortality rates and resulted in a slight negative effect on the biology and detoxification enzymes of C. carnea. Our results indicate that both sublethal and lethal concentrations of cyantraniliprole can successfully suppress S. littoralis and A. ipsilon populations. They also suggest that C. carnea, as a generalist predator, is compatible with cyantraniliprole under the modelled realistic field conditions. In future investigations, insights into the effects of cyantraniliprole on S. littoralis, A. ipsilon, and C. carnea under field conditions will be required to appropriately validate our results.

The Synergistic Effect of Lemongrass Essential Oil and Flometoquin, Flonicamid, and Sulfoxaflor on Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae): Insights into Toxicity, Biochemical Impact, and Molecular Docking.

The whitefly, Bemisia tabaci (Genn.), is one of the most dangerous polyphagous pests in the world. Eco-friendly compounds and new chemical insecticides have gained recognition for whitefly control. In this study, the toxicity and biochemical impact of flometoquin, flonicamid, and sulfoxaflor, alone or combined with lemongrass essential oil (EO), against B. tabaci was studied. In addition, a molecular docking study was conducted to assess the binding affinity of the tested compounds to AchE. Based on the LC values, the descending order of the toxicity of the tested compounds to B. tabaci adults was as follows: sulfoxaflor > flonicamid > flometoquin > lemongrass EO. The binary mixtures of each of the tested compounds with lemongrass EO exhibited synergism in all combinations, with observed mortalities ranging from 15.09 to 22.94% higher than expected for an additive effect. Sulfoxaflor and flonicamid, alone or in combination with lemongrass EO, significantly inhibited AchE activity while only flonicamid demonstrated a significant impact on α-esterase, and none of the tested compounds affected cytochrome P450 or GST. However, the specific activity of P450 was significantly inhibited by the lemongrass/sulfoxaflor mixture while α-esterase activity was significantly inhibited by the lemongrass/flometoquin mixture. Moreover, the lemongrass EO and all the tested insecticides exhibited significant binding affinity to AchE with energy scores ranging from -4.69 to -7.06 kcal/mol. The current findings provide a foundation for utilizing combinations of essential oils and insecticides in the integrated pest management (IPM) of B. tabaci.

Insights into the toxicity, biochemical activity, and molecular docking of Cymbopogon citratus essential oils and citral on Spodoptera littoralis (Lepidoptera: Noctuidae).

Insecticide resistance is a significant problem in insect management that can result from several processes including target-site change and increased activity of detoxifying enzymes. Spodoptera littoralis is one of the most resistant insect pests. For more effective insect management, alternatives to synthetic pesticides are encouraged. One of these alternatives is essential oils (EOs). Cymbopogon citratus EO and its main constituent citral were, therefore, considered in this study. The results revealed that C. citratus EO and citral exhibited significant larvicidal activity against S. littoralis, and the former was insignificantly more toxic than the latter. Additionally, treatments significantly affected the activity of detoxification enzymes. Cytochrome P-450 and glutathione-S-transferase were inhibited, while carboxylesterases, a-esterase and ß-esterase, were induced. The molecular docking study indicated that citral bonded with the amino acids cysteine (CYS 345) and histidine (HIS 343) of cytochrome P-450. This result suggests that interaction with cytochrome P-450 enzyme is one key mechanism by which C. citratus EO and citral act in S. littoralis. The results of our study are hoped to contribute to a better understanding of the mechanism of action of essential oils at the biochemical and molecular levels and provide safer and more efficient pest management solutions for S. littoralis.

Growth Optimization and Rearing of Mealworm (Tenebrio molitor L.) as a Sustainable Food Source.

As a sustainable food source for humans, mealworms (Tenebrio molitor) have a great deal of potential, due to the fact that they have a very favorable nutritional profile and a low environmental impact. For meal production, feed formulation and optimization are important. The mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) is the most consumed insect in the world. Mealworms were given a variety of diets, including wheat bran as constant diet supplemented with different levels of Ospor (Bacillus clausii) at 0.002 g, 0.004 g, 0.006 g, and 0.008 g; imutec (Lacticaseibacillus rhamnosus) at 0.2 g. 0.4 g, 0.6 g, and 0.8 g; fungi (Calocybe indica) at 250 g, 500 g, and 750 g; yeast (Saccharomyces cerevisiae) at 50 g, 100 g, and 150 g; and wheat bran (standard diet) were examined in complete randomized design (CRD). Different parameters, i.e., the larval, pupal, and adult weight, size, life span, and nutritional profile of mealworm were studied. When compared with other insect growth promoters, only wheat bran was discovered to be the most efficient. It generated the heaviest and longest larvae at 65.03 mg and 18.32 mm, respectively, as well as pupae weighing 107.55 mg and 19.94 mm, respectively, and adults weighing 87.52 mg and 20.26 mm, respectively. It was also determined that fungi (C. indica) and ospor (B. clausii) promoted faster larval development than yeast (S. cerevisiae) and imutec (L. rhamnosus). Larval mortality was also greater in the imutec (L. rhamnosus) and yeast (S. cerevisiae) diets than the others. No pupal mortality was recorded in all diets. Furthermore, the protein content of Tenebrio. molitor raised on a diet including fungi (C. indica) was the highest at (375 g), with a content of 68.31%, followed by a concentration of (250 g) with a content of 67.84%, and wheat bran (1 kg) (normal diet) with the lowest content at 58.91%. T. molitor larvae fed a diet supplemented with bacterial and fungal had lower fat and ash content than bran-fed T. molitor larvae (standard diet). Wheat bran (normal diet) had the highest fat at 16.11%, and ash at 7.71%. Hence, it is concluded that wheat bran alone or diet containing fungi (C. indica) and ospor (B. clausii) performed better in terms of growth, and these diets and protein content are recommended for the mass rearing of mealworms.