The insecticidal activity is the result of a series of complex interactions between toxic substances as ligands and insect’s enzymes as targets. Actually, synthetic insecticides used in pest control programs are harmful to the environment and may affect non-target organisms; thus, the use of natural products as pest control agents can be very attractive. In the present work, the toxic effect of aniseed (Pimpinella anisum L.) essential oil (EO) and its nanoemulsion (NE) against the red flour beetle Tribolium castaneum, has been evaluated. To assess the EO mode of action, the impact of sub-lethal concentrations of aniseed EO and NE was evaluated on enzymatic and macromolecular parameters of the beetles, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), total protein, total lipids and glucose. Finally, a molecular docking study was conducted to predict the mode of action of the major EO and NE components namely E-anethole, Limonene, alpha-himalachalene, trans-Verbenol and Linalool at binding site of the enzymes AST and ALT. Herein, the binding location of the main compounds in both proteins are discussed suggesting the possible interactions between the considered enzymes and ligands. The obtained results open new horizons to understand the evolution and response of insect-plant compounds interactions and their effect predicted at the molecular levels and side effects of both animal and human.

In this study, the single and common effects of temperature (20, 25 and 30 ± 1˚C) and eggplant varieties (Classic, 0111, and Anan) on the developmental performance and heat requirements of Coccinella undecimpunctata L. and Cheilomenes propinqua isis (Mulsant) were examined. The predators were fed upon Aphis gossypii Glover that reared on the three eggplant Solanum melongena (L.) varieties. The two-way ANOVA showed that there was significant effects of temperature and host plant varieties on the total developmental times of both predators. However, the interaction between temperature and host plant variety interaction had only significant effect on the total developmental times of C. undecimpunctata. The results also revealed that the developmental times (DT) of both predators were decreased with increasing the temperature, whereas the developmental rates increased. Based on lower developmental threshold (T 0 ) values, the more tolerant stage for coldness was the pupal stage of both C. undecimpunctata and C. propinqua isis on the three eggplant varieties. On the contrary, the more sensitive stage for low temperature degrees differed for both species: the eggs stage for C. undecimpunctata and the larval stage for C. propinqua isis. The minimum (T 0 ) values for the entire development of both predators were recorded on Classic variety. The heat units (degree-days, DD's) estimated for each stage showed that aphids produced on Classic variety lowered the amount of heat required by both predator species to complete their development. Further, the larval stage of both predatory species required more heat units to develop at each aphid-host plant variety combination than other stages. These results suggest that eggplant var. Classic has to be considered, in mass rearing programs, to produce a high nutritional prey for both predator species. This might maximize the population of these predators. As well, 30 °C would multiply the population of both predators under the same rearing conditions, and thus has to be generalized.

No abstract

Insect glutathione S-transferases (GSTs) serve critical roles in insecticides and other forms of xenobiotic chemical detoxification. The fall armyworm, Spodoptera frugiperda (J. E. Smith), is a major agricultural pest in several countries, especially Egypt. This is the first study to identify and characterize GST genes in S. frugiperda under insecticidal stress. The present work evaluated the toxicity of emamectin benzoate (EBZ) and chlorantraniliprole (CHP) against the third-instar larvae of S. frugiperda using the leaf disk method. The LC50 values of EBZ and CHP were 0.029 and 1.250 mg/L after 24 h of exposure. Moreover, we identified 31 GST genes, including 28 cytosolic and 3 microsomal SfGSTs from a transcriptome analysis and the genome data of S. frugiperda. Depending on the phylogenetic analysis, sfGSTs were divided into six classes (delta, epsilon, omega, sigma, theta, and microsomal). Furthermore, we investigated the mRNA levels of 28 GST genes using qRT-PCR under EBZ and CHP stress in the third-instar larvae of S. frugiperda. Interestingly, SfGSTe10 and SfGSTe13 stood out with the highest expression after the EBZ and CHP treatments. Finally, a molecular docking model was constructed between EBZ and CHP using the most upregulated genes (SfGSTe10 and SfGSTe13) and the least upregulated genes (SfGSTs1 and SfGSTe2) of S. frugiperda larvae. The molecular docking study showed EBZ and CHP have a high binding affinity with SfGSTe10, with docking energy values of −24.41 and −26.72 kcal/mol, respectively, and sfGSTe13, with docking energy values of −26.85 and −26.78 kcal/mol, respectively. Our findings are important for understanding the role of GSTs in S. frugiperda regarding detoxification processes for EBZ and CHP.

The present work was conducted to evaluate the effect of eight insecticides against red palm weevil (RPW), Rhynchophorus ferrugineus under laboratory and field conditions. The insecticides were studied namely, Chlorpyrifos, Diazinon, Ethion, Fenitrothion, Fipronil, Methomyl, Phenthate and Profenofos. Under laboratory condition results showed that, Chlorpyrifos was the most effective insecticide against the egg stage of RPW, while Fipronil was the most effective one against larval and pupal stage, and Methomyl recorded the highest effect against the adult stages (♀, ♂). At field condition Data revealed that, at the concentration of 3ml/L, all level of the tested insecticides caused 100% recovery expect Methomyl which reached 90% recovery only. Using 2ml/L of the tested insecticides revealed 100% recovery with Fipronil, and 90% with Chlorpyrifos and Phenthoate, while it was 80% with Ethion, Fenitrothion and Profenofos. Diazinon and Methomyl revealed only 60 and 50% recovery, respectively. It worth mentioning that Fipronil seams as the most effective one followed by Chlorpyrifos and Phenthoate.