he efficiency and biochemical effects of certain insecticides belonging to different groups namely: flubendiamide (diamide), pyridalyl (phenoxy-pyridaloxy), clothianidin (neonicotinoide), fipronil (phenylpyrazole) and spirotetramat (tetramic acid) and pirimiphos-methyl (Ops) were tested against 2nd larval instar of Spodoptera littoralis laboratory strain using dipping technique. The efficacy of the tested insecticides are arranged as follows to LC50 values. The results showed that flubendiamide was the superior toxicant insecticides ( LC50 1.03 ppm) followed by pyridalyl (2.13 ppm) then fipronil (7.42 ppm), clothianidin (26.87ppm), pirimiphos-methyl (76.31 ppm) and spirotetramat (431.91 ppm). Biochemical effects of the tested insecticides on acetylcholine esterase (AChE), glutathione-s-transferases (GST), adenosinetriphosphatase (ATPase), phenoloxidase, total calcium, and total protein were determined in the treated larvae. Data showed highest significant increase at AChE activity in treatment of fipronil by change% (70.59), while treatment with pirimiphosmethyl recorded highest significant decrease by change% (-56.41). Whereas, all treatments recorded increase in GST activity except pirimiphosmethyl recorded non significant decrease. All insecticides treatments were showed a decrease in phenoloxidase activity the highest decrease recorded by pirimiphos-methyl treatment by change % (- 53.06). Regarding change percentage of ATPase, activity data recorded significant increase with pirimiphos-methyl treatment by (72.91%).  However, total protein in all treatments showed a significant decrease. On the other hand, treatment with pirimiphos-methyl recorded a significant decrease in total calcium and the corresponding change % was   (- 6.0%). Previous data confirmed the mode of action of the novel tested insecticides.

Different formulations of pepper mint oil, i.e. bulk, nano-emulsion and nano-encapsulation were evaluated against 2nd and 4th instar larvae of the cotton leafworm Spodoptera littoralis (Boisd.). Their effects on enzymatic activities and bionomics were also investigated. Transmission Electron Microscopy (TEM) showed that the mean particle size of the prepared nano-emulsion ranged between 20-90nm. The encapsulation efficiency and loaded capacity percentages exhibited that distilled H2O was more suitable than ethanol in preparation of nano-encapsulation particles. Bioassay treatments showed LC50's on 2nd instars larvae were 70.59, 12.23 and 21.72 ppm for pepper mint oil, pepper mint nano-emulsion and loaded nanoemulsion, respectively. While on 4th instars these values were 80.47, 26.14 and 67.69 ppm, respectively. LC90's on 2nd instars were 104.75, 33.97 and 30.14 for pepper mint oil, pepper mint nanoemulsion and loaded nano-emulsion, respectively. While on 4th instars these values were 177.66, 71.37 and 102.29 ppm. Toxicity index and relative potency proved that nano-emulsion was more effective than loaded nano-emulsion, while the bulk preparation was the least effective one. Results of enzymatic activities showed marked effects of the three formulations of mint oil, significant inhibitions  were recorded for amylase, invertase, trehalase, protease and alkaline phosphatase, while significant increase in activities of cuticle phenoloxidase and chitinase. Effects of adding the three formulations to artificial diet of 2nd instar showed significant effects of the insect bionomics. Larvae durations, percentage mortalities, were increased as well as larval malformations. Also, pupal duration, percentage pupal mortality and pupal malformation were increased, while pupal weight was decreased. Adults longevity showed insignificant effects, while female fecundity and egg % fertility showed significant responce.

Newly ecdysed fourth instar larvae of the cotton leafworm, Spodoptera littoralis (Boisd.) were treated with LC50 of ecdysone agonist methoxyfenozide, to provide better insights into physiological symptoms and aspects induced by it as a mimic to the 20-hydroxyecdysone (20-E) action. Larvae ingest methoxyfenozide died within 2-3 days, and being trapped within their excuvae. They stopped feeding shortly before ecdysis. Treatment neither accelerated ecdysis nor ceased feeding, as soon as the larvae ingest such 20-E mimic. The continuous binding of the compound to the ecdysteroid receptors of S. littoralis larvae increased the titre of enzymes regulated by 20-E during the experimental time (3 days). Chitinase and phenoloxidase were activated after 6 and 12 hr from methoxyfenozide administration, respectively. The compound had no effect on chitin production, but endocuticle chitin degradation during moulting might be depressed as illustrated by the presence of higher amount of N-acetylglucosamine in control larvae than methoxyfenozide treated. It is suggested that methoxyfenozide might induces a precocious moult by initiating moulting cycle, but its main toxic effect is due to the fact that its level remains high during moulting and don’t decrease for allowing other hormones necessary for successful moulting to be released.

A comparison on the larvicidial activity of four commercial bacterial and viral bioagents, Profect®, Virotecto®, Viroset® and Protecto® were evaluated on the 2nd and 4th larval instars of Spodoptera littoralis (Biosd.). The LC50 values showed 1.35, 1.52, 1.57 and 1.61 mg/ ml against 2nd instar larvae, respectively. On the other hand, the LC50 values recorded 2.03, 2.5, 2.72 and 3.01 mg/L. on 4th instar larvae of S. littoralis using the above mentioned commercial bioagent products, respectively. The effect on four isozymes, i.e., ,  esterase (EST), glutamate oxaloacetate transaminase (GOT), malate dehydrogenase (MDH) and alcohol dehydrogenase (ADH) were evaluated. The obtained results indicated differences in the activity of the isozymes in treated 4th instar larvae as compared to untreated larvae.