Percentage Of Larval Mortality Research Articles

Toxicity studies for indigenous Bacillus thuringiensis isolates from Malang city, East Java on Aedes aegypti larvae

ObjectiveTo investigate the toxicity of indigenous Bacillus thuringiensis (B. thuringiensis) isolates from Malang City for controlling Aedes aegypti (Ae. aegypti) larvae. MethodsSoil samples were taken from Purwantoro and Sawojajar sub-districts. Bacterial isolation was performed using B. thuringiensis selective media. Phenotypic characteristics of the isolates were obtained with the simple matching method. The growth and prevalence of spores were determined by the Total Plate Count method, and toxicity tests were also performed on the third instar larval stage of Ae. aegypti. The percentage of larval mortality was analysed using probit regression. The LC50 was analysed by ANOVA, and the Tukey HSD interval was 95%. ResultsAmong the 33 selected bacterial isolates, six were obtained (PWR4-31, PWR4-32, SWJ4-2b, SWJ4-4b, SWJ-4k and SWJ5-1) that had a similar phenotype to reference B. thuringiensis. Based on the dendrogram, all of the bacterial isolates were 71% similar. Three isolates that had a higher prevalence of reference B. thuringiensis were PWR4-32, SWJ4-4b and SW5-1, of which the spore prevalence was 52.44%, 23.59%, 34.46%, respectively. These three indigenous isolates from Malang City successfully killed Ae. aegypti larvae. The PWR4-32 isolates were the most effective at killing the larvae. ConclusionsSix indigenous B. thuringiensis isolates among the 33 bacterial isolates found in the Sawojajar and Purwantoro sub-districts were toxic to the third instar larvae of Ae. aegypti. The PWR4-32 isolates were identical to the reference B. thuringiensis and had 88% phenotype similarity. The PWR4-32 isolates had the highest spore prevalence (52.44%), and the early stationary phase occurred at 36 h. The PWR4-32 isolates were the most effective at killing Ae. aegypti larvae (LC50–72 h=2.3×108 cells/mL).

Virulence potential of Metarhizium anisopliae s.l. isolates on Rhipicephalus (Boophilus) microplus larvae

The use of entomopathogenic fungi to control arthropods has been reported worldwide for decades. The aim of the present study was to evaluate the virulence of 30 Metarhizium anisopliae s.l. Brazilian isolates from different geographical regions, hosts or substrates on the larvae of Rhipicephalus (Boophilus) microplus ticks under in vitro conditions to the selection of virulent isolates in order to be further used in biological control programs. The current study confirmed the lethal action of M. anisopliae s.l. isolates on R. (B.) microplus larvae with different mortality levels, usually directly proportional to the conidia concentration. No relationship was found between the origin of the isolate and its virulence potential or between the virulence potential and conidia production. Three isolates (CG 37, CG 384 and IBCB 481) caused a high percentage of larval mortality, reaching LC50 at 106conidiaml−1, thus requiring a lower conidia concentration to cause an approximately 100% larval mortality. The results of this study suggest that these three isolates are the most promising for use in programs aimed at microbial control in the field.

Evaluation of the efficacy of three indigenous strains of entomopathogenic nematodes from Meghalaya, India against mustard sawfly, Athalia lugens proxima Klug (Hymenoptera: Tenthredinidae).

The objective of this study was to evaluate the efficacy of three indigenous strains of entomopathogenic nematodes (EPN) from Meghalaya, India, namely Heterorhabditis indica Poinar, Karunakar and David, Steinernema thermophilum Ganguly and Singh, and Steinernema glaseri (Steiner) against the last instar larva of mustard sawfly, Athalia lugens proxima Klug, a serious pest of mustard and radish in India. The larvae of A. lugens proxima were exposed to 10, 25, 50, 75 and 100 infective juveniles (IJs) concentration of each nematode species in Petri dishes. Percentage larval mortality and nematode reproduction in insect larvae was studied. The sawfly larvae were found to be susceptible to all the three EPNs tested, but the degree of susceptibility to infection varied from among nematode species. Based on LC50 value, H. indica was the most pathogenic species. Nevertheless, S. thermophilum and S. glaseri also showed a high insect mortality. This study also revealed that all the three test nematodes are also able to propagate in the host cadaver and produce first generation infective juveniles. However, H. indica produced significantly more number of IJs per insect larva than the other two nematode species. The progeny production was recorded to be the least in case of S. glaseri. In conclusion, our findings suggest that of the three indigenous EPNs studied, H. indica and S. thermophilum have good potential as biological control agents against mustard sawfly, A. lugens proxima.

Assessments the toxic effects of entomopathogenic bacterium, Bacillus thuringeinsis subsp. kurstaki, and methomyl insecticide on larval instars of the greater sugarcane borer; Sesamia cretica (Lederer)

This study was conducted to evaluate the efficacy of the bio-insecticide Bacillus thuringiensis (Dipel 2x ® 6.4 % WP) against, 1 st and 2 nd instar Larvae of Sesamia cretica compared with methomyl (Lannate 90 % SP). After 48 hours from treatment, The LC50 value of B. thuringiensis for 1 st instar and 2 nd larvae were 0.00526 and 0.7 gm, respectively. While the LC50 of methomyl after 24h. for 1 st instar and 2 nd larvae were 3394 and 5481 ppm, respectively. After treatment of 1 st and 2 nd instars larvae of S. cretica with LC50 concentrates of B. thuringiensis, the average larval duration of S. cretica were (36.53 & 24.69) and (33.78& 20.31) days for treated and untreated, respectively. In addition, the pupation percentage was (47 & 92 %) and (18 & 84 %) for treated and untreated, respectively. The larval mortality percentage was (53 & 8 %) and (82 & 16 %) for treated and untreated, respectively. The pupal weight for (treated & untreated), S. cretica were (0.1887 & 0.184 gm) and (0.1842 & 0.1601 gm) when it treated as 1 st and 2 nd instars larvae, respectively. Furthermore, the pupal duration were (12.14 & 10) and (10.44 & 9.83 days) for (treated & untreated), when S. cretica treated as 1 st and 2 nd instar larvae, respectively. The total adult emergence for 1 st instar and 2 nd instar larvae were (94 & 100%) and (100 & 100%) for treated and untreated, respectively. On the other hand results indicated that, after treatment of 1 st and 2 nd instar larvae of S. cretica with LC50 concentrates of methomyl, the average larval duration of S. cretica were (31.41 & 24.69) and (33.87& 20.31) days for treated and control, respectively. The pupation percentage was (34 & 92 %) and (28& 84 %) for treated and untreated when S. cretica treated as 1 st and 2 nd instars larvae, respectively. The larval mortality percentages were (66 & 8 %) and (72 & 16 %) for treated & untreated, respectively. The pupal weight for treated and control, were (0.1626 & 0.184 gm) and (0.1994 & 0.1601 gm), respectively. The pupal duration were (12.41 & 10) and (10.83 & 9.83) days for treated and untreated, respectively. The total emergence percentage for 1 st instar larvae were (100 & 100 %) and (85.7& 100%) for 2 nd instar larvae for each (treated & untreated), respectively.

Larvicidal activity of isolated compound 5-(2,4-dimethylbenzyl) pyrrolidin-2-one from marine Streptomyces VITSVK5 sp. against Rhipicephalus (Boophilus) microplus, Anopheles stephensi, and Culex tritaeniorhynchus

The aim of the present study was to assess the larvicidal property of marine actinobacterial compound 5-(2,4-dimethylbenzyl) pyrrolidin-2-one (DMBPO) extracted and isolated from Streptomyces VITSVK5 sp. tested against the larvae of Rhipicephalus (Boophilus) microplus Canestrini (Acari: Ixodidae), Anopheles stephensi Liston, and Culex tritaeniorhynchus Giles (Diptera: Culicidae). The isolate bacteria was taxonomically characterized, identified, and designated as Streptomyces VITSVK5 sp. The crude extract was loaded on silica gel column and eluted with chloroform:methanol. The isolated pure compound was analyzed by thin layer chromatography using chloroform and methanol as the solvent system and confirmed by high-performance liquid chromatography. The structure of the purified compound was established from infrared, ultraviolet, (1)H-nuclear magnetic resonance (NMR), (13)C-NMR, and mass spectral data. The chemical shift assignments obtained for the aliphatic compound from (1)H-NMR corresponding to the molecular formula C(13)H(17)NO. Bioassay-guided fractionation led to the isolation of compound which was identified as DMBPO. In the present study, Streptomyces VITSVK5 sp. crude extract and different fractions were tested against the larvae of parasites at the concentration of 1,000ppm. Those fractions showing 100% mortality in 24h alone was selected for further column chromatographic separation. The purified compound, C(13)H(17)NO, was tested in the concentrations of 500, 250, 125, 62.5, and 31.25ppm and observed the percent larval mortality of 100, 70, 64, 40, and 28 against R. microplus; 100, 79, 63, 36, and 22 against A. stephensi; and 100, 84, 67, 42, and 27 against C. tritaeniorhynchus, respectively. The crude extract showed parasitic effects after 24h of exposure at 1,000ppm, and parasite mortality was observed against the larvae of R. microplus (LC(50) = 210.39ppm, r (2) = 0.873); A. stephensi (LC(50) = 169.38ppm, r (2) = 0.840); and C. tritaeniorhynchus (LC(50) = 198.75ppm, r (2) = 0.887). The maximum efficacy was observed in purified marine actinobacterial compound DMBPO with LC(50) and r (2) values against the larvae of R. microplus (84.31ppm, 0.889); A. stephensi (88.97ppm, 0.817), and C. tritaeniorhynchus (74.95ppm, 0.781), respectively. The control (distilled water) showed nil mortality in the concurrent assay.

Screening for feeding deterrent activity of herbal extracts against the larvae of malaria vector Anopheles subpictus Grassi.

This no-choice, laboratory study focuses on the feeding of homogeneous powdered, dried, yeast with different plant extracts on mosquito fourth-instar larvae to determine the effects on their mortality. Screening for antifeedant activity of plant extracts with some known medicinal attributes could lead to the discovery of new agents for vector control. The aim of this study was to investigate the antifeedant activity of crude leaf hexane, ethyl acetate, acetone, and methanol extracts of Andrographis lineata Wallich ex Nees. (Acanthaceae), Anisomeles malabarica (L.) Sims. (Lamiaceae), Argemone mexicana L. (Papaveraceae), Aristolochia bracteolata Lam. (Aristolochiaceae), Chrysanthemum indium L. (Asteraceae), Datura metal L. (Solanaceae), Eclipta prostrata L. (Asteraceae), and Sesbania grandiflora (L.) Pers. (Fibaceae) against the fourth-instar larvae of Anopheles subpictus Grassi (Diptera:Culicidae). All the crude extracts showed antifeedant activity in a dose-dependent manner. The plant extracts exhibited a significant antifeedant activity after 24 and 48 h of exposure; however, the highest larval mortality was found in leaf ethyl acetate extract of A. malabarica, acetone extract E. prostrata, methanol extract of A. lineata, C. indium, and S. grandiflora after 24 h (LC(50) = 2.53, 2.82, 2.31, 2.56, and 2.08 mg/mL; LC(90) = 6.40, 8.06, 7.45, 6.98, and 6.20 mg/mL), respectively. The hexane extract of A. lineata, D. metal, methanol extract of A. bracteolata and E. prostrata showed larval mortality after 48 h (LC(50) = 3.05, 2.11, 3.00, and 2.18 mg/mL; LC(90) = 9.06, 6.22, 8.23, and 5.77 mg/mL), respectively. One hundred percent larval mortality was observed in methanol extract of A. lineata, and C. indium after 24 h and the hexane extract of A. lineata and D. metal after 48 h at 10 mg/100 mL. The methanol extracts of A. lineata and C. indium significantly increased larval mortality in comparison to larvae fed with untreated diet. Bacillus thuringiensis subsp. israelensis is widely accepted as a biological pesticide because of its highly specific activity against dipteran insects without adverse effects on other organisms. The feeding deterrent activity of different herbal extracts against the larvae of malaria vector A. subpictus exhibited significantly lower toxicity compare with the bio larvicides, B. thuringiensis. These results suggest that the methanol extract of A. lineata, C. indium, the hexane extract of A. lineata and D. metal have the potential to be used as an ideal eco-friendly approach for the control of the medically important vector A. subpictus. These findings corroborate traditional insecticidal application of selected plants and the results can be extended for the control of mosquitoes.

Biological screening of araripe basin medicinal plants using Artemia salina Leach and pathogenic bacteria

Background:Many medicinal plant species from the Araripe Basin are widely known and used in folk medicine and for commercial manufacturing of phytotherapeutic products. Few ethnobotanical and pharmacological studies have been undertaken in this region, however, in spite of the great cultural and biological diversity found there.Materials and Methods:Extracts of 11 plant species collected from Ceará state, Brazil, were subjected to the brine shrimp lethality test in order to detect potential sources of novel cytotoxic, antitumor compounds. The larvicidal activity, based on the percentage of larval mortality, was evaluated after 24 h exposure to the treatments. Results:All species tested showed good larvicidal activity as compared to a reference compound and literature data. The extract from Vanillosmopsis arborea was the most active with an LC50 of 3.9 μg/ml. Best results were shown by Lantana montevidensis against Pseudomonas aeruginosa [minimum inhibitory concentration (MIC) 8μg/ml] and Escherichia coli (MIC 32 μg/ml), Zanthoxylum rhoifolium against E. coli (MIC, 256 μg/ml) and Staphylococcus aureus (MIC 64 μg/ml) and Croton zenhtneri against S. aureus (MIC 64 μg/ml).Conclusion:Chemical tests indicated that a wide variety of natural product classes was present in those extracts that showed significant activities in the bioassays.

COMBINED APPLICATION OF TWO ENTOMOPATHOGENIC NEMATODES, HETERORHABDITIS INDICA AND STEINERNEMA ASIATICUM TO CONTROL THE RICE LEAF FOLDER, CNAPHALOCROSIS MEDINALIS (GOEN.).

ABSTRACT In this study, the efficacy of two entomopathogenic nematode species, Heterorhabditis indica and Steinernema asiaticum were evaluated against the larvae of the rice leaf folder, Cnaphalocrosis medinalis and the greater wax moth, Galleria mellonella. Combined inoculation of H. indica and S. asiaticum each at 75 IJs/larva resulted in faster larval mortality on C. medinalis (24.6 h) and G. mellonella (31 h). The percent larval mortality caused by H. indica alone was resulted significantly more (90% on G. mellonella and 60% on C. medinalis) than S. asiaticum (10% on G. mellonella and 40% on C. medinalis). Progeny produced by H indica and S. asiaticum was significantly more (84134 and 80458 IJs/larva respectively) on G. mellonella than they produced on C. medinalis larva (4843 and 4330 IJs/larva respectively). The combined use of entomopathogenic nematodes may offer an integrated approach to increase the efficacy of control of the rice leaf folder, Cnaphalocrosis medinalis and it could be a viable component in the Integrated Pest Management (IPM) where other control measures are ineffective or cannot be imposed.

Entomopathogenic nematode- Heterorhabditis indica and its compatibility with other biopesticides on the Greater wax moth- Galleria mellonella (L.)

Pathogenic effect of an indigenous entomopathogenic nematode, Heterorhabditis indica and commercial biopesticides of three fungal pathogens (M. anisopliae, B. bassiana and T. viride), one antagonistic bacteria (P. fluorescence), and two neem based biopesticides (Neem and Nimor) were tested on the Greater wax moth, Galleria mellonella larva under laboratory condition. The efficacy of the biopesticides was tested individually or in combination with H. indica. Pathogenic interaction on G. mellonella larva by H. indica and biopesticides was assessed at every twelve hour interval after storage. Significant differences in the percentage of larval mortality were determined among the biopesticide treatments. When tested in isolation, B. bassiana imposed greater mortality on host larva (40%) when compared to other biopesticides; while P. fluorescence and H. indica combination proved to be the most efficient causing 100% mortality on G. mellonella after 24 h of storage. Progeny produced by H. indica on single G. mellonella was found to be more (140108 IJs/larva) in the combination treatment with T. viride. Pathogenicity influence of H. indica when exposed with other biopesticides on host larva, have proved to be more virulent and compatible. The results on pathogenicity of entomopathogenic nematode- H. indica on G. mellonella larvae are a novelty in the field of biological control. Understanding the interactions between entomopathogenic nematodes and other soil microorganisms may be the key for success in IPM programme.

Entomopathogenic nematode- Heterorhabditis indica and its compatibility with other biopesticides on the Greater wax moth- Galleria mellonella (L.).

Pathogenic effect of an indigenous entomopathogenic nematode, Heterorhabditis indica and commercial biopesticides of three fungal pathogens (M. anisopliae, B. bassiana and T. viride), one antagonistic bacteria (P. fluorescence), and two neem based biopesticides (Neem and Nimor) were tested on the Greater wax moth, Galleria mellonella larva under laboratory condition. The efficacy of the biopesticides was tested individually or in combination with H. indica. Pathogenic interaction on G. mellonella larva by H. indica and biopesticides was assessed at every twelve hour interval after storage. Significant differences in the percentage of larval mortality were determined among the biopesticide treatments. When tested in isolation, B. bassiana imposed greater mortality on host larva (40%) when compared to other biopesticides; while P. fluorescence and H. indica combination proved to be the most efficient causing 100% mortality on G. mellonella after 24 h of storage. Progeny produced by H. indica on single G. mellonella was found to be more (140108 IJs/larva) in the combination treatment with T. viride. Pathogenicity influence of H. indica when exposed with other biopesticides on host larva, have proved to be more virulent and compatible. The results on pathogenicity of entomopathogenic nematode- H. indica on G. mellonella larvae are a novelty in the field of biological control. Understanding the interactions between entomopathogenic nematodes and other soil microorganisms may be the key for success in IPM programme.

DeterminaÇão da CL90 e TL90 do isolado IBCB66 de Beauveria bassiana (Ascomycetes: Clavicipitaceae) para o controle de Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

The objective of this research was to evaluate the pathogenicity and the virulence of the IBCB66 isolate of Beauveria bassiana on infected larvae of Rhipicephalus (Boophilus) microplus. The IBCB66 fungus strain was used as standard isolates of B. bassiana against R. (B.) microplus larvae. The larval bioassay tests using the IBCB66 isolate were carried out to determine the (Lethal Concentration) LC50, LC90, (Lethal Time) LT50 and LT90. The IBCB66 fungus strain was tested at six different concentrations (5x10(6), 10(7), 5x10(7), 10(8), 5x10(8) and 10(9) conidia.mL(-1)) to determine the percentage of larval mortality. In addition, a Probit analysis was also performed. Total larval mortality was observed eighteen days after the beginning of the test in the group treated with 5x10(9) conidia.mL(1). The LC50 and LC90 were 3x10(7) and 5x10(8) respectively and the LT50 and LT90 were 10 and 16 days.

External and internal elimination of supernumerary larvae in the whitefly parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae)

The solitary parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is one of the key biological control agents of the whitefly Bemisia argentifolii Bellows & Perring, also known as B. tabaci (Gennadius) B-biotype (Homoptera: Aleyrodidae). We present new information on its biology, and particularly about larval elimination during the first instar in cases of superparasitism. For the first time, physical elimination of supernumerary larvae was observed, both outside and inside the host. These findings are documented with confocal microscopy images and video recordings. We observed more than 350 B. argentifolii nymphs, parasitized with one, two or more than two larvae. Physical attack took place only when parasitoid eggs were laid in contact with each other. In this case the percentage larval mortality outside the host was significantly higher (45.7%) than in cases of single larvae (12.0%) or larvae hatched under the same host but not in contact with each other (23.3%). These new findings are important in view of a possible horizontal transfer of a parthenogenesis inducing Wolbachia bacterium from a thelytokous to an arrhenotokous strain, with the aim of augmenting the biological control of B. argentifolii.

Diversity, occurrence, and life characteristics of natural entomopathogenic nematode populations from La Rioja (Northern Spain) under different agricultural management and their relationships with soil factors

Natural entomopathogenic nematode (EPN) populations were surveyed in La Rioja (Northern Spain) during two consecutive years (2003–2005) to study their diversity, occurrence, and life characteristics under different agricultural management representing natural areas and perennial and annual crops from organic and conventional systems. Native EPN species and strains were identified using morphological and molecular characteristics. Virulence, infection cycle length and reproductive potential were assessed using Galleria mellonella larvae. The EPN occurrence was evaluated through abundance, recovery frequency, larval mortality percentage and EPN population density. EPNs were also related to selected soil physical and chemical variables as well as to some soil pollutants such as heavy metals and organochlorine pesticide residues. Only two steinernematids species were identified: Steinernema feltiae was observed throughout all seasons from natural and agricultural areas and Steinernema carpocapsae in summer and autumn of 2004 from perennial crops only. The virulence of native strains was lower than other previously isolated Spanish strain from natural areas or crop field edges. EPN abundance and recovery frequency indicated that habitat type might influence EPNs occurrence stronger than seasonality with the intensity of agricultural management inversely affecting their distribution. Moreover, clay, P2O5, Zn, Cu and hexachlorobenzene contents negatively correlating with EPN population density. We consider that agricultural management should be taken into account if EPNs are going to be used as biological control agents.

Efficacy of Piper nigrum (Piperaceae) extract for control of insect defoliators of forest and ornamental trees

AbstractThe acute toxicities of an extract obtained from a plant within the Piperaceae family and related synthetic analogues were tested against four common Canadian forest pest insects. The acute toxicity of the extract from black pepper, Piper nigrum L., was assessed after 1, 24, and 72 h by the percent larval mortality. The 24 h LC50 estimates for the P. nigrum extract were (in order of decreasing sensitivity) 0.012% for the introduced pine sawfly, Diprion similis (Hartig) (Hymenoptera: Diprionidae), 0.053% for the forest tent caterpillar, Malacosoma disstria Hubner (Lepidoptera: Lasiocampidae), 0.282% for the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), and 0.998% for the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Torticidae). There was no significant increase in mortality after 72 h. Seventy percent of L. dispar larvae dropped off or moved from branches within 1 h of application of 0.2% P. nigrum extract, indicating that these compounds have a repellent effect. Pipercide and nor-pipercide were more toxic to L. dispar and M. disstria larvae than piperolein A and a P. sarmentosum Roxb. amide 72 h after either oral or topical administration of these compounds. Toxic effects of piperamides were more pronounced by oral ingestion. Ninety percent mortality of L. dispar larvae occurred following an oral dose of 5 µg pipercide in diet, whereas mortality was only 40% following topical treatment at 5 µg pipercide/insect. Whole Piper extracts might be useful for the control of sawflies and tent caterpillars in small-scale applications, based on the demonstrated efficacy and reduced risk potential.

SYNERGISM BETWEEN CIS-PERMETHRIN AND BENZOYL PHENYL UREA INSECT GROWTH REGULATORS AGAINST AEDES AEGYPTI LARVAE

Emulsifiable concentrate formulations of 2 insect growth regulator (IGR) benzoyl ureas (novaluron and diflubenzuron) and the pyrethroid cis-permethrin were individually bioassayed against late 3rd- or early 4th-stage larvae of susceptible Aedes aegypti. The emergence inhibition 50% were 0.038, 0.048, and 0.179 ppb for novaluron, diflubenzuron, and cis-permethrin, respectively. We also tested 1:1 (v:v) mixtures of cis-permethrin and benzoyl ureas. Emergence inhibition 50% for novaluron plus cis-permethrin and diflubenzuron plus cis-permethrin were 0.030 and 0.037, respectively, with combination indexes of 0.49 and 0.56, indicating a synergistic interaction between these insecticides. The percentage of larval mortality produced by 0.5 ppb of the mixtures of cis-permethrin and each IGR was compared to the addition of larval mortality produced in separated experiments by 0.25 ppb of each component, after 5, 9 and 13 days of continuous exposure. In all bioassays, the novaluron plus cis-permethrin mixture produced a significantly higher larvicidal effect (P < 0.05) compared with the individual contribution of each compound. The diflubenzuron plus cis-permethrin mixture showed significantly higher larval mortality (P < 0.05) compared with the contributive effect of each insecticide after 9 and 13 days of exposure, but there was no significant difference after 5 days of exposure.

Distribution of the entomopathogenic nematodes from La Rioja (Northern Spain)

Entomopathogenic nematodes (EPNs) distribution in natural areas and crop field edges in La Rioja (Northern Spain) has been studied taking into account environmental and physical–chemical soil factors. Five hundred soil samples from 100 sites of the most representative habitats were assayed for the presence of EPNs. The occurrence of EPNs statistically fitted to a negative binomial distribution, which pointed out that the natural distribution of these nematodes in La Rioja was in aggregates. There were no statistical differences ( p ⩽ 0.05) in the abundance of EPNs to environmental and physical–chemical variables, although, there were statistical differences in the altitude, annual mean air temperature and rainfall, potential vegetation series and moisture percentage recovery frequency. Twenty-seven samples from 14 sites were positive for EPNs. From these samples, twenty isolates were identified to a species level and fifteen strains were selected: 11 Steinernema feltiae, two S. carpocapsae and two S. kraussei strains. S. kraussei was isolated from humid soils of cool and high altitude habitats and S. carpocapsae was found to occur in heavy soils of dry and temperate habitats. S. feltiae was the most common species with a wide range of altitude, temperature, rainfall, pH and soil moisture, although this species preferred sandy soils. The virulence of nematode strains were assessed using G. mellonella as insect host, recording the larval mortality percentage and the time to insect die, as well as the number of infective juveniles produced to evaluate the reproductive potential and the time tooks to leave the insect cadaver to determinate the infection cycle length. The ecological trends and biological results are discussed in relationship with their future use as biological control.

Interactions Among White Spruce Tannins, &lt;I&gt;Bacillus thuringiensis&lt;/I&gt; subsp. &lt;I&gt;kurstaki&lt;/I&gt;, and Spruce Budworm (Lepidoptera: Tortricidae), on Larval Survival, Growth, and Development

The interactions among white spruce, Picea glauca (Moench) Voss, purified acetone tannin extracts (hydrolyzable and condensed tannin), Bacillus thuringiensis subsp. kurstaki Cry1A(c) delta-endotoxin strain HD-73 (Btk), and spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) on larval survival, growth, and development were investigated over the whole larval feeding period by using artificial diet supplemented with three concentrations of Btk toxins per milliliter of diet (0, 0.021, and 1.72 microg/ml) and three concentrations of foliar tannin extract (0, 8, and 15% dry mass basis). At high Btk concentration, tannin antagonized Btk potency against spruce budworm by lowering Btk-related larval mortality from 83 to 43%. At moderate Btk concentration tannin did not affect Btk potency. Host tree tannins antagonized not only the lethal effects of Btk toxin but also sublethal Btk-related impacts in terms of larval development, pupal weight, relative consumption rate, and growth rate. When alone in the diet, tannin negatively affected larval survival, growth, and development. Maximum potency of tannins against spruce budworm larvae (60% mortality) was reached at dietary concentrations corresponding to what is found in the plant (8% dry mass). The addition of Btk toxin in food containing tannin reduced percentage of larval mortality by one-third, indicating that Btk toxin can antagonize tannin potency against the insect. Development of Btk transgenic spruce trees should consider the antagonistic effect the toxin may have on the resistance conferred by tannins that have evolved naturally in spruce trees.

Pesticidal and insecticidal effect of &lt;I&gt;Campsis grandiflora&lt;/I&gt; (Thumb.)

Campsis grandiflora (Thunb.), the Indian trumpet creeper, is commonly grown for ornament. In the present study, the aqueous extract of the leaves of the climber was evaluated for its pesticidal and insecticidal activities. A direct relationship was observed between the dose and the percentage larval mortality. Dosage values as expressed in log terms were, 1.398, 1.301, 1.230, 1.176 and 1.079 for 0.25, 0.20, 0.17, 0.15 and 0.12 ppm dose concentrations, respectively. For the insecticidal study, the percentage insect mortality was found to increase with the corresponding increase in dosage, indicating a direct relationship between the two. Highest insect mortality of 80% was observed with 5.75 µg/insect, while the lowest mortality of 20% was found, when the dosage was minimum at 0.35 µg/insect. Keywords: instecticidal, pesticidal, Campsis grandiflora Journal of Pharmaceutical and Allied Sciences Vol. 3(1) 2006: 274-277

Atividade larvicida de óleos essenciais contra Aedes aegypti L. (Diptera: Culicidae)

In the search for alternative chemical control against Aedes aegypti L., many researches are developed and encouraged in order to find new insecticidal plant substances. In this work, the larvicidal effect of ten essential oils was tested on A. aegypti. The oils were extracted by steam distillation and their chemical composition determined by GL-chromatography coupled with mass spectroscopy. The essential oils were diluted in aqueous solutions of dimethyl sulfoxide with concentrations of: 100, 50, 10, and 1 mg/ml. The larvicidal activity, based on the percentage of larval mortality, was evaluated after 24h exposure to the treatments. The essential oil of Vanillosmopsis arborea Baker presented the highest larvicidal activity, with CL50 of 15.9 mg/ml and CL90 of 28.5 mg/ml. On the other hand the essential oil of O.gratissimum L. showed the lower activity with CL50 de 95,80 mg/ml and CL90 de 102,86 mg/ml.The results indicate that the tested essential oils, and particularly the V. arborea, are composed by substances with larvicidal properties for A. aegypti.

EVALUATION OF BACILLUS thuringiensis (BERLINER) FORMULATIONS AGAINST THE PINK BOLLWORM PECTINOPHORA gossypiella (SAUND.)

Laboratory experiments were carried out to investigate the effect of two bacterial commercial products of B. thuringiensis (Dipel 2x and Protecto) on eggs and the newly hatched larvae of pink bollworm, P.gossypiella. Different concentrations of both commercial products of B. thuringiensis were tested. The results showed that the percentage of larval mortality increased by increasing concentration and the period after treatment, calculated LC50s values after 3-7 days of treatment. Treatment of eggs did not affect, significantly, the hatchability. While the percentage mortality of newly hatched larvae produced from the treated eggs was high according to the concentrations used.