Sex pheromone of the cotton leafworm, Spodoptera littoralis

cis-9,trans-11-Tetradecadien-1-ol acetate (A) and cis-9,trans-12-tetradecadien-1-ol acetate (B), the same compounds as the female sex pheromone of Spodoptera litura, were identified as major components of the female sex pheromone of the cotton leafworm, Spodoptera littoralis. Compounds A and B were individually active, but the activity was synergistically enhanced by mixing the two compounds. The male response was optimal with mixture ranging from 5 : 1 to 20 : 1 of compounds A and B, respectively. Fifty per cent of the male moths of S. littoralis responded to the 20 : 1 mixture at the 10^?7 μg level; they responded at a concentration 100-fold lower than did male moths of S. litura. A partially purified extract of females of S. litura stimulated male moths of S. littoralis. Similarly a partially purified extract of S. littoralis was also active for the male moths of S. litura. The extract of females of S. litura, however, was 1000 times less active for male moths of S. littoralis than was the exrtact of females of S. littoralis, suggesting that a compound(s) is present in the extract of S. litura that inhibits the response of males of S. littoralis.     

A novel tyrosine kinase activity in the cotton leafworm,Spodoptera littoralis

A rapid, highly-specific ELISA for tyrosine kinases readily detects such activity in crude extracts prepared from rat mammary epithelial and fibroblastic cells that have been stimulated with epidermal growth factor or basic fibroblast growth factor. Tyrosine kinase activity is also found in extracts of pupae of the cotton leafworm, Spodoptera littoralis. Both the mammalian and the insect tyrosine kinases are ATP-dependent. Both cytosol and membrane-associated (Triton-X-100-soluble) fractions of Spodoptera littoralis pupae contain tyrosine kinase activity. The growth factor-stimulated tyrosine kinase activities in extracts of growth factor-stimulated rat mammary cells are inhibited by genistein and an analogue of erbstatin: methyl 2,5-dihydroxycinnamate. However, the tyrosine kinase activities present in pupae of Spodoptera littoralis are not sensitive to these inhibitors, suggesting that the major tyrosine kinases of Spodoptera littoralis pupae may be distinct from the growth factor-stimulated mammalian tyrosine kinases.     

Ingestion and excretion of fucose by the larva of the egyptian cotton leafworm,Spodoptera littoralis

Spodoptera littoralis larvae were fed l-fucose mixed with sucrose, on Styropor lamellae, and their excretions were analysed by paper chromatography. Analysis of the main peak obtained showed that more than half of the fucose ingested was excreted as free fucose. This result was obtained both in experiments with radioactive fucose and by conventional chemical quantitation (silver nitrate method) of the peak. Two further peaks were shown by acid hydrolysis followed by sodium borohydride reduction to consist of fucose disaccharides and trisaccharides, respectively.     

Some physiological,biochemical and histopathological effects of Artemisia monosperma against the cotton leafworm,Spodoptera littoralis

The effect of Artemisia monosperma wild plant hexane extract on some biological and physiological aspects of Spodoptera littoralis, as well as some biochemical and histopathological changes after treatment with this extract have been studied. The results indicated that treatment with larvae for two days revealed satisfactory effects in larval mortality (50%) and in larval weight and prolonged the effect in the pupal stage. Also the treatment reduced the food consumption and the amount of faeces of the tested larvae which led to a significant reduction in the final body weight with 76.4%. Treatment also extended the time of food passage through the midgut to 3.2 h compared to 1.38 h in control, and the larvae had a smaller midgut. The enzymatic activity of the digestive enzymes amylase and invertase revealed a significant inhibition in the treated larvae. Also transaminase enzyme activity (AST and ALT) reduced after treatment. The results of phosphatase enzyme activity (ACP and ALP) showed a potent inhibitory effect on both enzymes which more was pronounced in ALP than ACP activity, the percent inhibition being 73.8% and 30.6%, respectively. The histopathological effects of A. monosperma treatment on the midgut of Spodoptera littoralis revealed that the epithelium membrane was exfoliated and completely destroyed. Meanwhile, epithelia cells were strongly vacuolated and considerably elongated. Boundary lines between the cells disappeared.     

Potency of Bacillus thuringiensis and Bacillus subtilis against the cotton leafworm,Spodoptera littoralis (Bosid.) Larvae

The biological activities of two species of bacteria isolated from soil of cotton fields identified as Bacillus subtilis strain NRC313 (BS NRC313) and Bacillus thuringiensis strain NRC335 (BT NRC335) were evaluated against the third larval instar of the cotton leafworm, Spodoptera littoralis (Boisd.). The different entomopathogenic bacteria of BS NRC313and BT NRC335 contained 10 × 10⁸ cell/ml, and caused mortality of 100 and 97.3% for the above mentioned strains, respectively. Concentrations of 2.5 × 10⁸ to 10 × 10⁸ cell/ml of strains BS NRC313 and BT NRC335 were applied to the larvae: LC₅₀ were 3.3 × 10⁸ and 3.9 × 10⁸ cell/ml respectively. The influence of exposure to toxin concentrations manifested in terms of decreasing the adult emergence and prolongation of the generation period. The percentage of larvae that survived and succeeded to pupate increased by decreasing the concentration. The longevity of adult emergence that resulted from larvae treated with Bacillus subtilis were 6.0 ± 0.51 and 9.0 ± 0.63 days at 5 × 10⁸ and 2.5 × 10⁸ cell/ml, respectively compared with 9.8 ± 0.47 in control. The results indicated that Bacillus subtilis was more potent than Bacillus thuringiensis. Field applications of B. thuringiensis, B. subtilis and Reldan achieved 55.6, 67.4 and 89.4% reduction of the cotton leafworm larvae Spodoptera littoralis in clover plants under field conditions.     

Repellent and insecticidal activities of Melia azedarach L. against cotton leafworm, Spodoptera littoralis (Boisd.)

A crude acetone extract and oil of ripe fruits from Melia azedarach L. were evaluated against the 2nd and 4th instar larvae of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae). Both oil and extract exhibited highly significant growth inhibition at all concentrations tested, while the oil of M. azedarach recorded higher insecticidal activity against both instars than the crude extract. GC-MS analysis of the oil revealed the presence of linoleic acid methyl ester, oleic acid methyl ester, and free oleic acid as the main components in addition to hexadecanol, palmitic acid, methyl esters of stearic acid and myristic acid. Fatty acids and their esters were not only the main constituents of essential oil from the ripe fruits of M. azedarach, but also mainly responsible for the insecticidal and growth inhibition activity against S. littoralis.     

Bioefficacy of cadmium and lead on cotton leafworm Spodoptera littoralis (Lepidoptera: Noctuidae) larvae

The sensitivity of Spodoptera littoralis second and fourth instar larvae to the heavy metals cadmium (Cd) and lead (Pb) was investigated under laboratory conditions. Both Cd and Pb, even, at very low concentrations, had relatively high toxic effects on S. littoralis larvae. Cd was more toxic to S. littoralis larvae than Pb. In addition, the mean percentage feeding deterrence (FDI%) of Cd and Pb was concentration-dependent. The nutritional indices (consumption index, growth rate, efficiency of converted ingested and digested food, and approximate digestibility) of S. littoralis second and fourth instar larvae were more affected in Cd-treatments compared with those of Pb-treatments. Therefore, the presence of such heavy metals in the environment would exert an adverse impact on S. littoralis larvae and their development.     

Angiotensin-converting enzyme in Spodoptera littoralis: molecular characterization, expression and activity profile during development

The characterization of the full-length angiotensin-converting enzyme (ACE) cDNA sequence of the lepidopteran Spodoptera littoralis is reported in this study. The predicted open reading frame encodes a 647 amino acids long protein (SlACE) and shows 63.6% identity with the Bombyx mori ACE sequence. A 3D-model, consisting of 26 alpha-helices and three beta-sheets, was predicted for the sequence. SlACE expression was studied in the embryonic, larval and pupal stages of S. littoralis and in different tissues of the last larval stage by reverse-transcribed PCR. This revealed that the gene is expressed throughout the life cycle and especially in brain, gut and fat body tissue of the last stage. These results are in agreement with a role of ACE in the metabolism of neuropeptides and gut hormones. In addition, ACE activity has been studied in more detail during development, making use of a fluorescent assay. High ACE peptidase activity coincides with every transition state, from embryo to larva, from larva to larva and from larva to pupa. A peak value in activity occurs during the early pupal stage. These results indicate the importance of SlACE during metamorphosis and reveal the high correlation of ACE activity with the insect's development, which is regulated by growth and developmental hormones.     

The analysis of flight paths of male Egyptian cotton leafworm moths, Spodoptera littoralis, to a sex pheromone source in the field

ABSTRACT. The flight of male Spodoptera littoralis (Boisd.) (Noctuidae) towards a pheromone source was recorded during the early part of the night using a cine camera and an image intensifier. The cine films were analysed frame by frame to produce flight tracks from which it was possible to calculate the mean advance rate of moths towards the pheromone source and their projected ground speed, for a series of positions downwind of the source. As wind speed was measured the moth's air speed was also estimated. The moths compensated for changes in wind speed by varying their air speed, hence maintaining a ground speed independent of wind speed. The ground speed itself was found to decrease as moths flew closer to the pheromone source.     

Distribution and metabolism of exogenous ecdysteroids in the egyptian cotton leafworm Spodoptera littoralis (lepidoptera: noctuidae)

After ingestion of various amounts of either [³H]ecdysone or [³H]20-hydroxyecdysone (0.8 ng to 10 μg) by sixth instar larvae of the Egyptian cotton leafworm Spodoptera littoralis, apolar metabolites are rapidly detected in the gut and frass. Hydrolysis of the apolar products with Helix hydrolases releases solely [³H]ecdysone or [³H]20-hydroxyecdysone, respectively. This, coupled with the formation of chemical derivatives (acetonide and acetate) which cochromatograph with authentic reference compounds on hptlc and hplc demonstrates that these apolar metabolites consist of ecdysone or 20-hydroxyecdysone esterified at C-22 with common long-chain fatty acids. The major fatty acids have been identified by RP-hplc and their contribution to the mixture determined. In contrast, [³H]ecdysone injected into the haemolymph of S. littoralis is metabolized to yield 20-hydroxyecdysone, ecdysonoic acid, and 20-hydroxyecdysonoic acid. Thus, two different pathways exist for the metabolism of ecdysteroids in this species. In addition to an essentially polar pathway operating on injected and endogenous ecdysteroids, exogenous ecdysteroids entering the gut of S. littoralis are detoxified, yielding apolar ecdysteroid 22-fatty acyl esters which are rapidly excreted. The significance of these results in relation to the effects of ingested ecdysteroids on S. littoralis is discussed. Arch. Insect Biochem. Physiol. 34:329–346, 1997. © 1997 Wiley-Liss, Inc.     

Role of Challenger pesticide and plant extracts on some physiological parameters of the cotton leafworm,Spodoptera littoralis (Boisd.)

Fourth instar larvae of cotton leafworm, Spodoptera littoralis (Boisd.), fed on castor bean leaves treated with sub-lethal concentrations of both alcohol and hexane extracts of Egyptian conyza and Challenger 36% SC insecticide as well to study their effects on mortality, food consumption and utilisation of food. The tested insecticides exhibited relatively high mortality in alcoholic extract of Egyptian conyza (5.0% concentration) followed by Challenger (1.0% concentration). Results showed a slight reduction in the consumption index for larvae treated with both alcoholic extract and Challenger at low concentrations, while hexane extract (5%) recorded significant increase. The approximate digestibility (AD) was reduced in all treatments of alcoholic extract and the relative growth rate insignificantly decreased at 5% concentration, whereas AD increased for larvae fed on Challenger 0.25% concentration. The lower concentration of alcoholic extract of conyza and all treatments of Challenger pesticides induced insignificant decrease in the efficiency of conversion of the ingested food, while hexane extract exhibited insignificant increase. Challenger at all tested concentrations achieved insignificant decrease in the efficiency of the conversion of digested food with respect to the control.     

Inheritance of Bacillus thuringiensis Cry1C resistance in Egyptian cotton leafworm,Spodoptera littoralis (Lepidoptera: Noctuidae)

A field strain of Spodoptera littoralis Biosduval was selected against Cry1C toxin derived from Bacillus thuringiensis entomocidus for 10 subsequent generations under laboratory conditions. Selection pressure resulted in a 29‐fold resistance ratio compared with the susceptible strain. Inheritance of Cry1C resistance was partially dominant and autosomal on the basis of bioassay response to Cry1C toxin in a reciprocal cross between male and/or female F₁. Consistent with earlier findings, resistance was recessive at high concentrations of Cry1C toxin. However, the dominance of resistance increased as the concentration of Cry1C decreased. Analysis of survival and growth of progeny from a backcross (F₁ × resistance strain) suggested that resistance was controlled by either a single or a few loci in cotton leafworm.     

Isolation, gene expression and solution structure of a novel moricin analogue, antibacterial peptide from a lepidopteran insect, Spodoptera litura

An antibacterial peptide was isolated from a lepidopteran insect, Spodoptera litura. The molecular mass of this peptide was determined to be 4489.55 by matrix assisted laser desorption/ionization-time of flight mass (MALDI-TOF MS) spectrometry. The peptide consists of 42 amino acids and the sequence has 69-98% identity to those of moricin-related peptides, antibacterial peptides from lepidopetran insects. Thus, the peptide was designated S. litura (Sl) moricin. Sl moricin showed a broad antibacterial spectrum against Gram-positive and negative bacteria. Sl moricin gene was inducible by bacterial injection and expressed tissue-specifically in the fat body and hemocytes. Furthermore, the solution structure of Sl moricin was determined by two-dimensional (2D) 1H-nuclear magnetic resonance (NMR) spectroscopy and hybrid distance geometry-simulated annealing calculation. The tertiary structure revealed a long alpha-helix containing eight turns along nearly the full length of the peptide like that of moricin, confirming that Sl moricin is a new moricin-like antibacterial peptide. These results suggest that moricin is present not only in B. mori but also in other lepidopteran insects forming a gene family.