Biosynthesized silver nanoparticles (Ag NPs) from isolated actinomycetes strains and their impact on the black cutworm, Agrotis ipsilon.

Nanomaterials have been produced with the use of bio-nanotechnology, which is a low-cost approach. Currently, research is being conducted to determine whether actinomycetes isolated from Egyptian soil can biosynthesize Ag nanoparticles (Ag NPs) and characterized by using the following techniques: Transmission electron microscopy (TEM), Dynamic light scattering (DLS), Fourier transforms infrared (FT-IR), Energy-dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy and X-ray diffraction (XRD). The most promising actinomycetes isolate were identified, morphologically, biochemically, and molecularly. Streptomyces avermitilis Azhar A.4 was found to be able to reduce silver metal nanoparticles from silver nitrate in nine isolates collected from Egyptian soil. Toxicity of biosynthesized against 2nd and 4th larval instar of Agrotis ipsilon (Hufn.) (Lepidoptera: Noctuidae) was estimated. In addition, activity of certain vital antioxidant and detoxifying enzymes as well as midgut histology of treated larvae were also investigated. The results showed appositive correlations between larval mortality percentage (y) and bio-AgNPs concentrations (x) with excellent (R2). The 4th larval instar was more susceptible than 2nd larval instar with LC50 (with 95% confirmed limits) =8.61 (2.76-13.89) and 26.44(13.25-35.58) ppml-1, respectively of 5 days from treatment. The initial stages of biosynthesized AgNps exposure showed significant increases in carboxylesterase (CarE) and peroxidases (PODs) activity followed by significant suppression after 5 days pos-exposure. While protease activity was significantly decreased by increasing time post-exposure. Midgut histology showed abnormality and progressive damage by increasing time post exposure leading to complete destruction of midgut cells after 5 days from exposure. These results make biosynthesized AgNPs an appropriate alternative to chemical insecticide in A. ipsilon management.

Pesticidal Effect of Leaves Extract of Different Plants on the Larvae of Cotton Leaf Worm, Spodoptera littoralis.

<b>Background and Objective:</b> The cotton leafworm, <i>Spodoptera littoralis</i> (Boisd.) (Lepidoptera: Noctuidae), represents the worst lepidopterous pest on most vegetable crops. Moreover, its host range is extensive because it is a polyphagous and cosmopolitan pest that can cause an estimated loss of nearly 25.8 to 100% of crop production. Natural controls have replaced pesticides due to the environmental damage that chemical pesticides cause. Eggplant, tomato, okra and pepper are Egypt's most significant vegetable crops and the leaves of these plants are cheap and can act as botanical and nontoxic pesticides. <b>Materials and Methods:</b> <i>Spodoptera littoralis </i>larvae were reared in the laboratory and plant leaves of eggplant, tomato, okra and pepper were extracted in the laboratory with organic solvents. Then, these extracts were applied to the larvae. Therefore, the histological sectors in larvae bodies were prepared and the changes were observed compared with the control. <b>Results:</b> This study proved the efficiency of all plant leaf extracts, especially those of eggplant and tomato leaves (LC₅₀ of 1191.9 and 1582.7 ppm, respectively). In contrast, okra and pepper leaf extracts had the highest LC₅₀ (3904.8 and 5431.6 ppm, respectively). Also, the abnormalities in the midgut and internal tissues were evident in the larvae treated with eggplant leaf extracts, followed by tomato leaf extracts and okra leaf extracts. Larvae treated with pepper leaf extracts were as normal as the control. <b>Conclusion:</b> The current study opens horizons to new plant extracts that are cheap and unused plant parts and make them helpful as new and good insecticides.