Egyptian Cotton Leafworm Spodoptera Littoralis Research Articles

Biochemical and toxicological effects of certain bioinsecticides on The Egyptian cotton leafworm Spodoptera littoralis

Biochemical and toxicological effects of certain bioinsecticides on The Egyptian cotton leafworm Spodoptera littoralis

Effect of four host plants on the life history and nutritional indices of Spodoptera Littoralis

The Egyptian cotton leafworm Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) is a pervasive and highly polyphagous insect pest. As S. littoralis has developed resistance to major classes of conventional insecticides and the use of these insecticides has caused negative impacts on the ecosystems, it is necessary to search for eco-friendly, cost-effective, and sustainable agents to control. This can be achieved by identifying the preferred host plant. The present study aimed at evaluating the impacts of four host plants– castor bean, tomato, potato, and cucumber on the various life-history traits and nutritional indices of S. littoralis. The concentrations of nitrogen, potassium, and phosphorous in the tested host plants were quantified. Newly hatched larvae were divided into four groups. Each group was fed only on one type of the four tested host plants until pre-pupal stage. Then, the life-history traits and nutritional indices were determined. Larvae fed on castor bean showed the highest adult emergence, weight of full-grown larvae, number of eggs per female, and egg-hatch percent, food consumption, relative growth rate, and food utilization efficiencies. Whereas, larvae fed on cucumber showed the lowest egg-hatch percent, food consumption, relative growth rate, and food utilization efficiencies. There was a positive correlation between nitrogen and phosphorous concentrations in the tested host plants and larval weight, with the highest concentrations in castor bean. Castor bean was the most preferred host plant.

Effects of phthalate and bisphenol plasticizers on the activity of glycolytic enzymes of the moth Spodoptera littoralis

Environmental plastic pollution has significantly increased in the recent decades, and severely impacts economies, human and biodiversity health. Plastics are made of several chemical additives, including bisphenol and phthalate plasticizers such as bisphenol A (BPA) and Di(2-ethylhexyl)phthalate (DEHP). In some animal species, both BPA and DEHP are known as endocrine disruptor compounds, and can alter physiological and metabolic homeostasis, reproduction, development and/or behavior. To date, the impacts of BPA and DEHP have mainly focused on vertebrates, and to a lesser extent, on aquatic invertebrates. Yet, the few studies which examined the effects of DEHP on terrestrial insects also revealed the impacts this pollutant can have on development, hormone titrations, and metabolic profiles. In particular, it has been hypothesized in the Egyptian cotton leafworm Spodoptera littoralis that the observed metabolic alterations could result from the energetic costs necessary for DEHP detoxification or to the dysregulation of hormonally-controlled enzymatic activities. To get additional insights into the physiological effects of bisphenol and phthalate plasticizers on the moth S. littoralis, larvae were fed with food contaminated by BPA, DEHP, or the mixture of both compounds. Then, activities of four glycolytic enzymes, hexokinase, phosphoglucose isomerase, phosphofructokinase, and pyruvate kinase were measured. BPA and/or DEHP had no effects on the activities of phosphofructokinase and pyruvate kinase. Conversely, BPA-contaminated larvae were characterized by a 1.9-fold increase in phosphoglucose isomerase activity, and BPA + DEHP-fed larvae had highly variable hexokinase activity. Overall, since no disruption of glycolytic enzyme was observed in DEHP-contaminated larvae, our work tended to demonstrate that exposure to bisphenol and DEHP increased the amount of oxidative stress experienced.

Individual and combined treatments with imidacloprid and spinosad disrupt survival, life-history traits, and nutritional physiology of Spodoptera littoralis

The Egyptian cotton leafworm Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) is a pervasive agricultural polyphagous insect pest. Because of the negative side-effects of conventional pesticides used in agricultural fields, safer alternatives for insect pest management are required. We evaluated here susceptibility, biological features, and nutritional indices of S. littoralis after treatment of 4th-instar larvae with the neonicotinoid imidacloprid and the spinosyn spinosad separately or in combination. Larvae were fed for three successive days on treated leaves of castor-bean Ricinus communis using leaf-dip technique (treatment period). In addition, in case of nutritional indices study, treated leaves were replaced by fresh untreated leaves for two successive days (recovery period). Spinosad was more toxic than imidacloprid, and their combination revealed additive effects based on the co-toxicity factor. Individual and combined treatments significantly decreased pupation rate, adult emergence rate, pupal weight, number of eggs laid per female, egg-hatch, and female longevity, compared to those of controls. Pupal and adult malformations were recorded. During the treatment period, nutritional indices were insecticide- and time-dependent. On the 2nd day of recovery, all nutritional indices of treated larvae were not significantly different, compared to those of controls. The results presented herein may help in developing more effective crop protection methodologies within integrated pest management of this insect.

Bioprospecting endophytic fungi for antifeedants and larvicides and their enhancement by gamma irradiation

The search and discovery of new natural products with antifeedant and larvicidal potentials to mitigate harmful insects are scientific pressing issues in the modern agriculture. In this paper, the antifeedant and larvicidal potentials of 69 fungal isolates were screened against the Egyptian cotton leafworm Spodoptera littoralis. A total of 17 isolates showed the insecticidal potentials with three promising isolates. These strains were Aspergillus sydowii, Lasiodiplodia theobromae, and Aspergillus flavus isolated from Ricinus communis (bark), Terminalia arjuna (Bark), and Psidium guajava (twigs), respectively. The effect of gamma irradiation on the antifeedant and larvicidal activities of the three strains was investigated. Exposure of the fungal spores to 1000 Gy of gamma rays significantly intensified both the antifeedant and larvicidal potentials. To identify compounds responsible for these activities, extracts of the three strains were fractionated by thin layer chromatography. The nature of the separated compounds namely, Penitrem A, 1, 3, 5, 8- tetramethyl- 4, 6-diethyl- 7- [2- (methoxycarbonyl)ethyl] porphyrin (from A. sydowii), Penitrem A, 2, 7, 12, 17-Tetramethyl-3, 5:8, 10:13, 15:18, 20-tetrakis (2,2-dimethylpropano) porphyrin (from A. flavus), N,N-Diethyl-3-nitrobenzamide, and Diisooctyl-phthalate (from L. theobromae) were studied by GC-MS analysis. These findings recommend endophytic fungi as promising sources of novel natural compounds to mitigate harmful insects.

Morphological description and population dynamic of Spodoptera littoralis (Boisduval, 1833) (Lepidoptera: Noctuidae)’s parasitoid on cabbage in South Côte d’Ivoire

The Egyptian cotton leafworm Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae) is among the serious cabbage pests in tropical countries. It can lead an intensive chemical insecticides use in market gardening perimeters. Alternative control methods such as biological control are necessary for the integrated management of this pest. The laboratory rearing of S. littoralis larvae sampled in […]

Susceptibility of the Egyptian Cotton Leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) to Entomocidal Crystal Proteins Cry1Ac and Cry 2Ab Baseline Responses

The present study maybe is the first attempt in Egypt to evaluate the effect of Entomocidal proteins (Cry toxins) from Bacillus thuringiensis (Bt)Cry 1Ac and Cry 2Ab againstthe Egyptian cotton leafworm Spodoptera littoralis. The cotton leafworm one of the important Lepidopteran species is the most important pests in cotton fields. It can be controlled using Genetically Modified (GM) crops expressing insecticidal Bt proteins like Bt cotton and Bt corn. The long-term success of this technology demands pest resistance management. Important information for the successful management of resistance is the baseline susceptibility of the different target pests to the different Bt proteins. The data on baseline susceptibility should enable risk assessors and managers to assess whether GM cotton produces a Bt protein in a high-dose to specific target organisms and resistance has evolved during the commercial cultivation of this GM cotton event. During this study, the toxicity of Cry 1Ac and Cry 2Ab from the bacterium Bacillus thuringiensis to larvae of S. littoralis was assessed using first instar larvae with diet incorporation bioassays. Larvae reared (4 generations) from 2 populations of S. littoralis collected from major cotton-growing regions of Sohag and Assuit Governorates were tested. The LC50 for the Assuit strain was 140.11 and 88.54 µg/ml forCry 1Ac and Cry 2Ab, respectively. While, the LC50 for the Sohag strain was 410.75 and 37.62 µg/ml for Cry 1Ac and Cry 2Ab, respectively. On the other hand, the laboratory strain was more sensitive for the same Cry’s (Cry 1Ac and Cry 2Ab) the LC50 was13.40 and 0.23 µg/ml, respectively. The lethal concentration (LC50) against S. littoralis for 2nd and 4th instars larvae when using the B. thuringiensis as spores (commercial product) was 1.16 and 2.49 for 2nd and 4th instars, respectively. This study is very important as a preliminary step and baseline ahead of the commercial cultivation and production of Genetically Modified cotton (Bt cotton).

Adipokinetic Hormones Enhance the Efficacy of the Entomopathogenic Fungus Isaria fumosorosea in Model and Pest Insects.

Insect adipokinetic hormones (AKHs) are neuropeptides with a wide range of actions, including the control of insect energy metabolism. These hormones are also known to be involved in the insect defence system against toxins and pathogens. In this study, our aim was to demonstrate whether the application of external AKHs significantly enhances the efficacy of the entomopathogenic fungus Isaria fumosorosea in a model species (firebug Pyrrhocoris apterus) and pest species (Egyptian cotton leafworm Spodoptera littoralis and pea aphid Acyrthosiphon pisum). It was found that the co-application of Isaria with AKHs significantly enhanced insect mortality in comparison to the application of Isaria alone. The mode of action probably involves an increase in metabolism that is caused by AKHs (evidenced by the production of carbon dioxide), which accelerates the turnover of Isaria toxins produced into the infected insects. However, several species-specific differences probably exist. Intoxication by Isaria elicited the stimulation of Akh gene expression and synthesis of AKHs. Therefore, all interactions between Isaria and AKH actions as well as their impact on insect physiology from a theoretical and practical point of view need to be discussed further.

Disturbance of the Main Body Metabolites in Larvae and Pupae of Spodoptera littoralis (Lepidoptera: Noctuidae) by Certain Sesquiterpene Compounds

The Egyptian cotton leafworm Spodoptera littoralis (Boisduval) is a dangerous pest of many field crops and vegetables in the world. The present study was conducted to investigate the disturbing effects of the sesquiterpene compounds, Farnesol, Nerolidol, and Bisabolol, on the main body metabolites in larvae and pupae of this insect. The newly moulted last (6th) instar larvae were treated with LC50 values of these compounds (33.67, 42.24 and 59.31 ppm, respectively) and the determination of the main metabolites was achieved in haemolymph and fat bodies of larvae and the homogenate of pupae. The most important results could be summarized as follows. The present study recorded predominant reducing effects of these compounds on the protein content in larvae and pupae with an exceptional enhancing effect of some compounds at certain ages of last instar larvae. Also, the lipid content in haemolymph and fat bodies of larvae as well as in the pupae was remarkably reduced. In addition, all compounds exhibited predominant reducing effects on the carbohydrate content in haemolymph and fat bodies of larvae and in the pupae, with two exceptions of increasing carbohydrate content in larval haemolymph (at 24 hr post-treatment) and in larval fat bodies by Nerolidol (at 72 hr post-treatment).

Impairing Effectiveness of Nerolidol, a Sesquiterpene Compound, on Adult Performance and Reproductive Potential of Egyptian Cotton Leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae).

Although Egyptian cotton leafworm Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) is native in Africa, it is distributed throughout the world. It is a serious polyphagous insect damaging more than 90 host plants of economic importance. The objective of the current study was to evaluate the disruptive impact of Nerolidol, a Sesquiterpene compound, on the most important parameters of adult performance and reproductive potential of this insect. The newly moulted larvae of 5th (penultimate) or 6th (last) instar larvae fed castor bean leaves previously treated with 7 concentrations of Nerolidol(400, 200, 100, 50, 25, 12.5& 6.25 ppm) for 24 hr. The most important results could be summarized as follows. Nerolidol exhibited an adulticidal activity only at the higher concentrations. Nerolidol exerted an anti-morphogenic activity against adult moths since some malformed adults were produced at the higher concentrations. Regardless the treated larval instar, Nerolidol induced the successfully emerged adults to live remarkably shortened total longevity and oviposition period, but the pre-oviposition period was generally prolonged. Nerolidol exhibited an inhibitory effect on the oviposition efficiency since the oviposition rate was deleteriously regressed, in a dose-dependent course. Nerolidol caused a disturbance of the reproductive capacity since fecundity and fertility were dramatically prohibited. After larval treatment with Nerolidol, the successfully mated adult females laid eggs with a significantly prolonged incubation period, especially at the higher concentration levels.

Bioefficacy of Farnesol, A Common Sesquiterpene, On the Survival, Growth, Development, and Morphogenesis of Spodoptera littoralis (Lepidoptera: Noctuidae).

Egyptian cotton leafworm Spodoptera littoralis (Boisduval) is a dangerous pest of many field crops and vegetables in the world. The present study was conducted to evaluate the toxicity of Farnesol and its effects on the growth, development, and morphogenesis of this insect. The newly moulted larvae of 5th (penultimate) or 6th (last) instar larvae were fed on castor bean leaves previously treated with 7 concentrations of Farnesol (400, 200, 100, 50, 25, 12.5 & 6.25 ppm) for 24 hr. The most important results could be summarized as follows. After treatment of 5th or 6th instar larvae with Farnesol, various mortalities were recorded among larvae, pupae, and adults. Depending onLC50values, Farnesol exhibited stronger insecticidal activity after treatment of 6th instar larvae(LC50= 33.67 ppm) than after treatment of 5th instar larvae(LC50= 36.56 ppm). Farnesol caused a serious reduction of larval weight gain and deleterious regression of the growth rate. The larval and pupal durations had been remarkably prolonged, in a dose-dependent course. Disruption of the developmental program was recorded as a failure of ecdysis after treatment of 5th instar larvae and production of larval-pupal intermediates, regardless the treated larval instar. Farnesol exerted considerable suppressing action on the pupation. At higher concentrations, Farnesol interfered with the adult emergence, since eclosion was completely prevented at the highest concentration and partially blocked at other concentrations. Irrespective of the treated larval instar, some deformed pupae were developed only at higher two concentrations of Farnesol.

Exploring essential oils of Slovak medicinal plants for insecticidal activity: The case of Thymus alternans and Teucrium montanum subsp. jailae

Thymus alternans and Teucrium montanum subsp. jailae are medicinal and aromatic plants, typical of Slovakian flora, producing bioactive essential oils. In the present study, we evaluated the insecticidal potential of the essential oils, obtained by hydrodistillation from the plant aerial parts and analysed by GC-MS, as insecticidal agents. For the purpose, they were assayed against three insect species acting as agricultural pests or vectors of medical relevance, such as the common housefly, Musca domestica L., the lymphatic filariasis vector, Culex quinquefasciatus and the Egyptian cotton leafworm Spodoptera littoralis; α-cypermethrin was tested as positive control. The two essential oils exhibited a different chemical profile, with monoterpenes and sesquiterpenes being the main fractions in the essential oils from Th. alternans and T. montanum subsp. jailae, respectively. Insecticidal tests showed that the T. montanum essential oil was effective against S. littoralis (LD50(90) = 56.7 (170.0) μg larva−1) and Cx. quinquefasciatus larvae (LC50(90) = 180.5 (268.7) mg L−1), whereas T. alternans essential oil displayed good toxicity against M. domestica adults (LD50(90) = 103.7 (223.9) μg adult−1). Overall, our results add useful knowledge about the potential of Slovakian flora as a source of botanicals for the eco-friendly management of insect pests and vectors.

Assessment of the Inhibitory Impact of Novaluron, A Recent Insect Growth Regulator, on the Reproductive Potential of Spodoptera littoralis (Boisd.)(Lepidoptera: Noctuidae).

The Egyptian cotton leafworm Spodoptera littoralis is one of the destructive pests of field crops in the tropical and subtropical areas of the world. The objective of the present study was to assess the impact of Novaluron on the reproductive potential of this pest. A series of concentrations (1.0, 0.1, 0.01, 0.001 & 0.0001ppm) was prepared and applied on the freshly molted penultimate instar larvae. Another series (0.1, 0.01, 0.001 & 0.0001 ppm) was prepared and applied on the newly molted last (6th) instar larvae. The results can be summarized as follows. The tested compound exhibited a predominantly inhibitory effect on the oviposition efficiency, regardless the concentration and time of larval treatment. Both fecundity and fertility had been drastically reduced, in a dose-dependent course, regardless the time of treatment. Irrespective of the concentration and time of treatment, Novaluron halted the embryonic development, since the incubation period of eggs was remarkably prolonged. In light of the present results, Novaluron acts as an antigonadotropic compound in S. littoralis.

Impairment of Development and Reproductivity of the Egyptian cotton leafworm Spodoptera littoralis Boisduval (Noctuidae: Lepidoptera) by Cycloheximide.

The Egyptian cotton leafworm, Spodopteralittoralis, is destructivepest of cotton and various crops in Egypt and someparts of the world. The present study was carried outaiming to assess the disruptive effects of cycloheximide on survival, growth,development, metamorphosis and reproductive potential of this pest. Four doses:180, 120, 60 and 30 µg/larva had been topically applied (once) onto the newlymoulted last instar larvae. cycloheximide exhibited toxic effect on larvae,pupae and adults.Unexpectedly, no mortality was observed at the highestdose.LD50 was estimated at 0.013 µg/larva.Themaximal weightsof the treated larvae increased and the larval growthwas remarkably enhanced. Thelarval and pupal durations were shortened.Some larvae appeared as'giant larvae', only at the lower two doses.They enlarged insize and appeared heavier than other treated and control larvae. They survived2-times longer period than of the control larvae and perished without pupation.Topical treatment of larvae only with the lower two doses induced a stateof suspended development, 'permanent prepupae' which failed to pupate.Cycloheximideexerted an inhibitory action on the pupation rate after treatment only with thelower three doses. Some deformed pupae were produced. The adult emergence wasconsiderably blocked at lower three doses.The oviposition wascompletely prevented, at the higher two doses, but partially inhibited at thelower two doses. No fecundity could be determined at the higher two dosesbecause no oviposition was carried out. At the lower two doses, fecundity wasdramatically reduced. All eggs failed to hatch indicating complete sterility ofS. littoralis.

Direct Effects of Temperature Changes on Biochemical and Enzymatic for Cotton Leafworm, Spodoptera littoralis (Boisd.)

It is important to understand the effects of increasing temperatures due to global warming on Egyptian cotton leafworm Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) which damages a wide variety of crops in the Middle East and is one of the major economic pests of cotton in Egypt. Therefore,we are investigating five different constant temperatures at 15, 20, 25, 30and 35oC as different thermal effects on biochemical parameters and enzymes of fourth larval instars. Biochemical analyses were performed to determine the effects of these different constant temperatures on the amount of total proteins, lipids, carbohydrates and free amino acids as well as metabolic, digestive, neural and detoxification enzymes. It's clear from the results that the total amount of proteins, free amino acids as well as, the activity levels of proteases were increased significantly by raising of temperatures to reach their maximum activities at 30oC. While the total amount of lipids, Carbohydrates were decreased significantly by raising of temperatures. Moreover, activity levels of amylase, invertase and Trehalase were decreased at 15oC.Amylase and invertase reached their maximum activity at 30oC,while Trehalase reached its maximum activity at 20oC. There was severe reduction in carbohydrate enzymes activities at 35oC. On other hands, the activity levels of total lipids and lipase were increased significantly at lower temperatures 15oC and 20oC, no significant changes were detected between other temperatures. The activity levels of GOT and GPT increased significantly and reached their maximum level at 20oC.However, GOT and GPT at other temperature were significantly different. The level of GST Enzyme was increased significantly at 30oC, while, its activity level was decreased at 15oC. Moreover, AchE, Alpha (EST-α) and beta esterase(EST-β) enzymes were increased gradually at 15,20 and 25 oC. They reached their maximum activities at 25oC followed by the reduction in activity levels at 30oC and 35oC.

FIELD AND SEMI FIELD APPLICATIONS FOR BIO AND CHEMICAL PESTICIDES ON COTTON LEAF WORM, Spodoptera littoralis (BOISD.) (LEPIDOPTERA : NOCTUIDAE)

Three bio insecticides Biolarve and Triamph derivate from emamectin benzoate and W-Bus which derivate from Bacillus thuringiensis (Bt), in addition to one organophosphorus insecticides Linker tested for their effects on 2nd and 4thlarval instars and egg masses (24, 48 and 72 h old) of the Egyptian cotton Leafworm Spodoptera littoralis (Boised) infested tomato crop under field and semi field conditions. The doses used were the recommended dose by Egyptian agricultural ministry. The obtained results showed that all insecticides were potent and effective in controlling S. littoralis caused highly mortality and reduced the number of all tested larval instars and egg masses. The bio pesticides caused lower mortalities percentage than the chemical one in case of initial kill calculations, but after one day till ten days caused higher mortalities percentage than the organophosphorus insecticides. The second larval instar recorded sensitive reaction than the fourth larval instar of S. littoralis, which shown more resistant to all examined insecticides.

Inhibition kinetics of acid and alkaline phosphatases by atrazine and methomyl pesticides

The main objective of this work was to investigate the kinetic characteristics of acid and alkaline phosphatases isolated from different sources and to study the effects of the herbicide atrazine and insecticide methomyl on the activity and kinetic properties of the enzymes. Acid phosphatase (ACP) was isolated from the tomato plant (Solanum lycopersicum L. var. lycopersicum); alkaline phosphatase (ALP) was isolated from two sources, including mature earthworms (Aporrectodea caliginosa) and larvae of the Egyptian cotton leafworm (Spodoptera littoralis). The specific activities of the enzymes were 33.31, 5.56 and 0.72 mmol substrate hydrolyzed per minute per milligram protein for plant ACP, earthworms ALP and cotton leafworm ALP, respectively. The inhibition kinetics indicated that atrazine and methomyl caused competitive–non-competitive inhibition of the enzymes. The relationships between estimates of Km and Vmax calculated from the Michaelis–Menten equation have been explored. The extent of the inhibition was different, as estimated by the values of the inhibition constant Ki that were found to be 3.34 × 10−3, 1.12 × 10−2 and 1.07 × 10−2 mM for plant ACP, earthworms ALP and cotton leafworm ALP, respectively, with methomyl. In the case of atrazine, Ki were found to be 8.99 × 10−3, 3.55 × 10−2 and 1.36 × 10−2 mM for plant ACP, earthworms ALP and cotton leafworm ALP, respectively.

Pathogenicity, Yield and DNA Genome Pattern of the Entomopathogenic VirusSpodoptera littoralisMulticapsid Nucleopolyhedrovirus (SpliMNPV) toSpodoptera littoralis(Boisduval) Under the Impact of Environmental Stress

The effect of temperature, ultraviolet (UV) radiation and sunlight on the pathogenicity, yield and DNA genome pattern of the entomopathogenic virus SpliMNPV to the Egyptian cotton leafworm Spodoptera littoralis (Boisduval) was studied. The viral pathogenicity in terms of larval mortality, and yield in terms of polyhedral inclusion bodies/g larval body weight, significantly increased with the increase of temperature; with optimal temperature of 30 °C for viral yield. However, the pathogenicity significantly decreased with the increase of the exposure period, under the stress of both UV radiation and sunlight, in case of non-shielded exposed viral samples. In contrast, sunlight and UV had no significant effect on the viral pathogenicity in shielded exposed samples. The viral yield significantly decreased with the increase of the exposure period to UV radiation. The same pattern also held true for the exposure to sunlight in case of non-shielded exposed samples without using a UV filter. The viral DNA genome pattern was not affected under the stress of temperature, UV-radiation (shielded samples), sunlight using a UV filter (shielded or non-shielded samples), and sunlight without using a UV filter (shielded samples). Whereas, the intensity of the viral DNA, in non-shielded samples, decreased gradually with the increase of the exposure period to UV radiation and sunlight without using a UV filter.

Microbial control of the cotton leafworm Spodoptera littoralis (Boisd.) by Egyptian Bacillus thuringiensis isolates

Four local Bacillus thuringiensis (Bt) isolates that had been serologically identified as Bt var. kurstaki (Btk2, Btk3, and Btk66) and Bt var. mexicanensis (Btm27), in addition to two reference strains (4D20 and 4AC1), were laboratory assayed as microbial control agents against the Egyptian cotton leafworm Spodoptera littoralis (Boisd.). Polymerase chain reaction (PCR) amplification analysis revealed that each of the six experimental strains carries, at least, a cry1 type gene which expresses a protein toxin active against lepidopterous insects. Additionally, PCR amplification results demonstrated that 4D20 and Btk66 contain the Lepidoptera- and Diptera-active cry2 type gene and that Btk66 contains Coleoptera-active cry7 and cry8 genes. Among the six strains, Btk66 and Btm27 were the most promising microbial control agents against S. littoralis. The present findings were the first to report that Btm27 (classified as B. thuringiensis var. mexicanensis) is a very potent microbial control agent against S. littoralis-tested larvae. For more characterization of these two isolates, the sspO gene was investigated as a molecular chronometer. The DNA sequencing results proved that Btk66 and Btm27 carry sspO open reading frames with identical nucleotide sequences, suggesting a strong phylogenetic relationship between the two strains.

Opportunistic nature of the mammalian microsporidia: experimental transmission of Trachipleistophora extenrec (Fungi: Microsporidia) between mammalian and insect hosts

Spores of Trachipleistophora extenrec, originally isolated from the muscles of the Madagascan insectivore Hemicentetes semispinosus and maintained by serial passage in severe combined immunodeficiency (SCID) mice, were fed to larvae of the Egyptian cotton leafworm Spodoptera littoralis. Extensive infection of larval tissues ensued and caused larval and pupal mortality. The development of T. extenrec in the insect host, studied both by light and electron microscopy, followed generally the same life cycle as in the mammalian host. However, some differences in the fine structure of the parasite grown in both types of hosts were found. Spores isolated from the insect host caused infection of SCID mice when injected intramuscularly. Our results suggest that T. extenrec may be originally an insect microsporidian. This likelihood is corroborated by its structural similarity and phylogenetic relationship to two other microsporidia having insects either as unique hosts (Vavraia culicis) or being able to infect both mammalian and insect host (Trachipleistophora hominis).