A new control strategy is required to face the resistance of the cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae),to chemical insecticides, and to decrease the pollution of the environment. Silver nanoparticles (AgNPs) were used to overcome these problems and to control S. littoralis at the immature stage. AgNPs were prepared by the reduction method. The prepared AgNPs were sphere-shaped with an average diameter of 20.73 nm. Several concentrations of AgNPs (50, 100, 200, 400, and 800 ppm) were used as insecticides against the third instar larvae of S. littoralis under laboratory conditions. The feeding treatments and adsorption via the integument produced malformations and morphological changes in the treated S. littoralis larvae. The larvicidal effect of AgNPs recorded LC50 equal to 224.8 ppm after 14 days of the application. Weight loss in the larvae and the pupae after treatment was significant with averages 47.13 and 60.41 percent, respectively. The treatment produced malformations in the shape and size of larvae and pupae. Some metal-detoxifying enzymes were significantly affected due to the treatment. There were quantitative and qualitative changes in the protein contents, in addition to a significant reduction in the total lipids and total carbohydrates of the treated larvae compared with the untreated larvae. The application of AgNPs against S. littoralis larva, as demonstrated by our findings, paves the way for new pest control options.

The confused flour beetle, Tribolium confusum, is a common insect that can be found in stores and homes and attacks a variety of commodities and stored foods. In the past, synthetic chemical insecticides were used to control them, which caused many negative health and environmental effects. Acetamiprid is a neonicotinoid insecticide with a novel mechanism of action, low toxicity for mammals, and a low environmental impact. The effectiveness of that insecticide against T. confusum was tested in this study. The toxicological bioassay was performed by contact application with different concentrations of acetamiprid. Our results indicated that the increased concentration and exposure periods significantly enhanced the mortality rate. The mortalities reached 20.6±1.12% and 92.6±1.86% at 1 ppm and 8 ppm concentrations of acetamiprid, respectively, after 14 days of exposure. The effects of acetamiprid on the fecundity and sterility of T. confusum have been assessed. Laboratory studies indicated that acetamiprid significantly reduced egg laying and hatching in comparison with the control. All acetamiprid concentrations used resulted in sterility in the treated adults. At the highest concentration (8 ppm), the sterility was 66.28%. The effects of acetamiprid on the activity of the acetylcholinesterase (AChE) enzyme were also investigated. It was observed that AChE from T. confusum was almost completely inhibited at the highest concentration. On the contrary, the level of the detoxifying enzyme, glutathione S-transferase, was increased in the treated samples. Acetamiprid's mutagenic effect on T. confusum was investigated by applying the median-lethal concentration (LC50), investigating DNA alteration for polymorphic numbers of genetic bands by using RAPD-PCR primers, and comparing it with the control. Results strongly suggest that acetamiprid causes mutagenic effects on T. confusum. The results recommended that acetamiprid can be used as a useful tool in pest management programs for T. confusum considering its insecticidal effects, which are evident at low applied concentrations and short exposure times.

The current investigation was conducted to study the efficacy of natural diatomaceous earth (DE) alone and combined with two fungal pathogens: Metarhizium anisopliae and Beauveria bassiana, as a new formulation against Spodoptera littoralis third instar larvae under laboratory conditions. When M. anisopliae, B. bassiana, and DE were applied alone, the mortalities of larvae were concentration-dependent. The LC50 values were 299.2, 391.5, and 572 ppm, respectively. The combination of DE with M. anisopliae and with B. bassiana enhances the efficacy of both. The LC50 values were 133.77 and 189 ppm, respectively, indicating a toxic potentiation effect. The results demonstrated that the application of DE in a binary combination with fungi significantly reduced the immune enzyme activity (phenoloxidase, prophenoloxidase, lysozyme) and protein concentration compared to the control. These findings are consistent with the theory that diatomaceous earth increases the effectiveness of entomopathogenic fungi against insects by causing cuticle damage, which increases conidial attachment and increases the availability of nutrients for conidial germination. It concluded that adding DE to entomopathogenic fungi helps in improving their quality and efficiency in reducing insect outbreaks, and it suggested participating in sustainable pest management of S. littoralis.