Chemical Control Of Insects Research Articles

Spatial and temporal distribution of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) and Euxesta spp. (Diptera: Otitidae) in the corn crop

The aim of this study was to verify the pattern and the spatial and temporal behavior of the corn earworm and corn-silk fly in the corn crop. Hybrid corn was planted without chemical insect control in one hectare, this area was divided into 100 plots of 100 m². For the occurrence of Euxesta spp. all parts of the plants were visually analyzed, whereas for Helicoverpa zea (Boddie) 10 ears were removed at random from each plot, totaling 1,000 ears per sample. Population fluctuation was related to the phenological stages of corn. For spatial behavior, the dispersion indices, frequency distribution models and geostatistics (Krigagem) were analyzed. The corn earworm (small and large) and corn-silk fly showed aggregate pattern and spatial behavior. The reach of caterpillars <1 cm had an area of influence greater than caterpillars > 1 cm, with spatial dependence being considered moderate. The corn-silk fly had a maximum area of influence of 1.33 ha with moderate and weak spatial dependence. The maps demonstrated that these insects occur dispersed throughout the corn area, but with aggregations influenced by the adjacent areas and edges of the crop. The largest occurrence of corn earworms was at the R3 stage. It was also found that the corn-silk fly followed the occurrence of the corn earworm. It is concluded that the studied pests have an aggregate spatial tendency in the corn crop and with the influence of adjacent areas, in addition to presenting related population peaks in the reproductive period of the corn crop.

Species diversity of different insect families trapped under beer-based volatile fermentation

BackgroundInsect species composition is an important phenomenon playing a significant role in the ecosystem. Chemical control of insects and pests releases toxic materials to the environment. These chemicals are dangerous to human populations. In this situation, there is a dire need to develop strategies to overcome the haphazard use of chemicals. The present investigations were carried out to explore the diversity of different insects attracted through bait fermentation.MethodsThe traditionally prepared bait fermentation was used to attract different insect populations both in treated (traps installed near field crops) and control traps (traps installed near invasive weed). Abundance, evenness, richness and equitability of these trapped insects were calculated. The chemical screening of bait fermentation was done using Gas Chromatography and Mass Spectrometry (GC–MS).ResultsSignificant difference (P < 0.05) in abundance of insect populations was found in treated compared to control trap. The insects of Noctuidae family recorded high Shannon- Wiener’s diversity index followed by Muscidae. Margalef’s index was recorded maximum in the treated traps (10.77) compared to those of control (8.09). The yielded index indicated that maximum richness was found in bait treated compared to control. The Shannon’s equitability’s values were investigated higher in Noctuidae (1.48), while, maximum evenness was observed in Muscidae (2.05) in treated trap. This fermentation was dried at room temperature and ground at 0.1 micron size. Our result showed significant (P < 0.05) effects of extraction times, with high yield in first extraction by polar solvents. Co-efficient of determination (R2= 0.87) recorded similar results in both extractions, however high root mean square error (0.97) recorded with bait + distilled water solvent showed linear arc line gave better performance. Finally, this fermentation was analyzed using GC–MS and recorded volatile compounds that were involved in the attraction of major and minor pests.ConclusionFermentation can help for the attraction of different families of insects of various crops. The field experiment suggested that this fermentation is economical, easily installed and consumed only 0.64 RMB/0.09 USD, including infrastructures per location. Bait fermentation is safe biochemical constituents and did not spread any toxic chemicals to the environment.

Entorno tecnológico y socioeconómico de la habichuela larga en el Caribe Húmedo de Colombia

La habichuela larga se cultiva en el sistema de producción de economía campesina. El objetivo del trabajo fue obtener información básica sobre la producción y los retornos económicos de la habichuela larga en el Caribe Húmedo de Colombia en el año 2018. No se evidencian trabajos anteriores en materia de caracterización tecnológica y socioeconómica. La información se obtuvo de una encuesta estructurada aplicada mediante el método de muestreo aleatorio simple a 16 productores de habichuela larga. Los retornos económicos se calcularon empleando patrones de costos y técnicas de análisis económico de rentabilidad. Los resultados demuestran que los productores tienen experiencia en cultivar la habichuela larga de tres a cuarenta años, bajo un sistema de agricultura familiar y de subsistencia; la superficie dedicada al cultivo varía de 0,2 a 0,5 ha. Predomina el uso de mano de obra familiar en un 75 %, el 100 % de los agricultores usa semilla no certificada, un 90 % realiza control manual de malezas y el 70 % hace control químico de insectos. Un 86 % de la producción tiene como destino el mercado local, y un 14 %, el consumo de las familias. Los costos de producción corresponden a $3.476.914,2 por hectárea, la producción media es de 4.950 kg ha-1, el precio de venta promedio es de $765 por kilogramo, lo cual genera una relación beneficio costo de 1,09 en cuatro meses del ciclo productivo y una rentabilidad de 8,9 %. Dado que las inversiones son bajas, se considera una producción eficiente, que garantiza la sostenibilidad en el tiempo.

Modeling Benefit–cost Analysis of Hemlock Wooly Adelgid Host Plant Resistance with Emphasis on Least-toxic Chemical Treatment Alternatives

Chinese hemlock (Tsuga chinensis) exhibits a high level of resistance to the exotic insect hemlock woolly adelgid (HWA; Adelges tsugae) relative to the native and widely planted eastern hemlock (Tsuga canadensis). Furthermore, both chinese and eastern hemlock exhibit similar autecologic and aesthetic characteristics in urban and suburban environments. This study provides a comparative 25-year economic benefit-cost analysis (BCA), tracking estimated establishment and insect control costs for the two tree species. Eastern hemlock survival requires insecticide treatments when growing within the range of HWA. Insect control scenarios used and evaluated in this study include annual horticultural oil spray, biannual horticultural oil spray, biennial imidacloprid soil drench, and no treatment. The chinese hemlock scenario did not include chemical insect control because of the species’ host plant resistance (HPR) to HWA. Benefits were estimated using the U.S. Department of Agriculture, Forest Service’s i-Tree tool, which estimates economic benefits for ecosystem services (expressed in dollars). Benefit–cost ratios (BCRs) were developed using the present value for 25-year benefit and cost streams at 2% and 4% discount rates. Payback periods were also estimated for all options that had a calculated BCR greater than one. The benefit–cost analyses for each insect control scenario were evaluated, compared, and assessed through the lens of market potential. The costs exceed the benefits for all of the eastern hemlock scenarios. The benefits exceed costs for the chinese hemlock scenario. Results suggest that chinese hemlock is a viable alternative to eastern hemlock in view of its HPR and reduced associated costs over time. If chinese hemlock becomes more widely planted, it is expected to produce greater BCRs relative to chemical control options as a result of the lack of required, ongoing insect control treatment costs.

Peptidergic control of the crop of the cabbage root fly, Delia radicum (L.) Diptera: Anthomyiidae): A role for myosuppressin

There is much interest in targeting neuropeptide signaling for the development of new and environmentally friendly insect control chemicals. In this study we have focused attention on the peptidergic control of the adult crop of Delia radicum (cabbage root fly), an important pest of brassicas in European agriculture. The dipteran crop is a muscular organ formed from the foregut of the digestive tract and plays a vital role in the processing of food in adult flies. We have shown using direct tissue profiling by MALDI-TOF mass spectrometry that the decapeptide myosuppressin (TDVDHVFLRFamide) is present in the crop nerve bundle and that application of this peptide to the crop potently inhibits the spontaneous contractions of the muscular lobes with an IC50 of 4.4 × 10−8 M. The delivery of myosuppressin either by oral administration or by injection had no significant detrimental effect on the adult fly. This failure to elicit a response is possibly due to the susceptibility of the peptide to degradative peptidases that cleave the parent peptide to inactive fragments. Indeed, we show that the crop of D. radicum is a source of neuropeptide-degrading endo- and amino-peptidases. In contrast, feeding benzethonium chloride, a non-peptide agonist of myosuppressin, reduced feeding rate and increased the rate of mortality of adult D. radicum. Current results are indicative of a key role for myosuppressin in the regulation of crop physiology and the results achieved during this project provide the basis for subsequent studies aimed at developing insecticidal molecules targeting the peptidergic control of feeding and food digestion in this pest species.

A Review of Perennial Ryegrass Endophytes and Their Potential Use in the Management of African Black Beetle in Perennial Grazing Systems in Australia.

The major insect pest of Australian cool temperate pastures is the root-feeding insect Heteronychus arator (African black beetle, ABB). Significant pasture damage can occur even at low ABB densities (11 individuals per square meter), and often re-sowing of the whole paddock is required. Mitigation of the effects of pasture pests, and in particular subterranean species such as the larval form of ABB, can be challenging. Early detection is limited by the ability to visualize above-ground symptoms, and chemical control of insects in soil is often ineffective. This review takes a look at the historical events that molded the pastoral landscape in Australia. The importation route, changes in land management and pasture composition by European settlers may have aided the establishment of ABB in Australia. Perennial ryegrass Lolium perenne is discussed as it is one of the most important perennial agricultural grasses and is widely-sown in moderate-to-high-rainfall temperate zones of the world. Endophytic fungi from the genus Epichloë form symbiotic relationships with cool season grasses such as Lolium perenne (perennial ryegrass). They have been studied extensively and are well documented for enhancing persistence in pasture via a suite of bioactive secondary metabolites produced by the fungal symbionts. Several well-characterized secondary metabolites are discussed. Some can have negative effects on cattle (e.g., ergovaline and lolitrems) while others have been shown to benefit the host plant through deterrence of insect pests from feeding and by insecticidal activity (e.g., peramine, lolines, ergopeptines). Various control methods for ABB are also discussed, with a focus on the potential role of asexual Epichloë endophytes.

Expression pattern and pharmacological characterisation of two novel alternative splice variants of the glutamate-gated chloride channel in the small brown planthopper Laodelphax striatellus.

Glutamate-gated chloride channels (GluCl) mediate fast inhibitory neurotransmission in invertebrate nervous systems. Although only one GluCl gene was presented in insects, it showed diverse alternative splicing that was speculated could affect channel function and pharmacology. In this study, we isolated GluCl cDNAs from adults of the small brown planthopper (SBPH) Laodelphax striatellus and showed that six L. striatellus GluCl variants (LsGluCl-AS, LsGluCl-BS, LsGluCl-CS, LsGluCl-AL, LsGluCl-BL, LsGluCl-CL) were present in the SBPH. The expression patterns of six variants differed among developmental stages (egg, first- to fifth-instar nymphs, male and female adults) and among the body parts (head, thorax, abdomen, leg) of the female adult SBPH. All the transcripts were abundant in the head of the adult. When expressed in African clawed frog, Xenopus laevis, oocytes, the two functional variants (LsGluCl-AS, LsGluCl-AL) had similar EC50 and IC50 values for L-glutamate and channel blockers picrotoxinin and fipronil. This study represents a comprehensive molecular, expression and pharmacological characterisation of GluCl in the SBPH. These findings should be useful in providing more opportunities to discover novel insect control chemicals. © 2016 Society of Chemical Industry.

Fungal pathogens and antagonists in root-soil zone in organic and integrated systems of potato production

AbstractOccurrence of culturable Fungi and Oomycota in root-soil habitat of potato cv. Owacja in organic and integrated production systems at Osiny (northern Poland) was compared in 2008-2010. The densities of both pathogens were significantly greater in the organic system. The eudominant fungal taxa (with frequency &gt; 10% in at least one habitat) included species of Fusarium + Gibberella + Haematonectria, Penicillium, Phoma and Trichoderma. The dominant taxa (with frequency 5-10%) included species from 13 genera. In the rhizoplane, rhizosphere and non-rhizosphere soil, the total density of potential pathogens was greater in the integrated system, and of potential antagonists in the organic system. Among eudominant and dominant pathogens, Fusarium oxysporum and Gibellulopsis nigrescens occurred at greater density in the integrated system and Haematonectria haematococca and Phoma spp. in the organic system. Among eudominant antagonists, Trichoderma species occurred at greater density in the organic system. The organic system provided more disease suppressive habitat than the integrated system. The occurrence of brown leaf spot and potato blight was however similar in both systems. The mean yield of organic potatoes (24.9 t · ha-1) was higher than the mean organic potato yield in Poland (21.0 t · ha-1) and similar to the mean in other European countries (Germany 25.1 t · ha-1, Great Britain 25.0 t · ha-1). The organic system, based on a 5-year rotation, with narrow-leafed lupin, white mustard and buckwheat as a cover crop, inorganic fertilization based on ground rock phosphate + potassium sulphate, and biological and chemical control of insects and diseases (Bacillus thuringiensis ssp. tenebrionis + copper hydroxide + copper oxychloride), may be recommended for use in central Europe.

Sustainability Assessment of Plant Protection Strategies in Swiss Winter Wheat and Potato Production

Production of arable crops in Switzerland is subsidized for services performed within the Proof of Ecological Performance (PEP) program, the crop protection part of which is based on IPM principles. Within PEP, chemical insect control must rely on those approved insecticides that are deemed harmless for beneficial arthropods. Approved insecticides potentially impacting beneficial arthropods may also be applied, but only if unavoidable and with an official permit. In order to assess the ecological and economic sustainability of this PEP program, a reference insecticide strategy illustrating the current PEP requirements was compared with other strategies. For this purpose, a sustainability assessment taking account of ecotoxicological risks and economic viability in addition to the preservation of beneficial arthropods was performed according to the SustainOS methodology. The results show that the one-off use of Audienz (spinosad) to control cereal leaf beetle (Oulema melanopus)—a key pest in winter wheat—would significantly improve sustainability vis-à-vis the reference (Nomolt (teflubenzuron) plus Biscaya (thiacloprid)). However, in the case of the Colorado potato beetle (Leptinotarsa decemlineata), in potato crops, where Audienz is considered the reference, no alternative would exhibit better sustainability. Moreover, the study shows that strategies using Novodor (Bacillus thuringiensis) protect beneficial species well but have the drawbacks of increased yield risk and higher costs. The conclusions drawn from these analyses allow recommendations for modifications of the PEP requirements for these two pest insects. The SustainOS methodology, a multi-step process combining expert knowledge with quantitative assessments including a sensitivity analysis of key target parameters and a rule-based aggregation of assessment results, yielded valuable insights into the sustainability of different crop protection strategies.

Effective selection criteria for assessing the resistance of stink bugs complex in soybean

Soybean plants with resistance to the stink bug complex are currently selected by extremely labor-intensive methods, which limit the evaluation of a large number of genotypes. Thus, this paper proposed the use of an alternative trait underlying the selection of resistant genotypes under field conditions with natural infestation: the weightof healthy seeds (WHS). To this end, 24 genotypes were evaluated under two management systems: with systematic chemical control of insects (management I), and without control (management II). Different indices were calculated using grain weight (Y P) of management I and WHS ofmanagement II (Y S). The high correlation between Y Sand the indices mean productivity, stress tolerance and geometric mean productivity, plus the agreement in determining the groups of genotypes with resistance and high yield indicate that WHS is a useful character insimultaneous selection for these traits.

GluCl a target of indole alkaloid okaramines: a 25 year enigma solved.

In 1989, indole alkaloid okaramines isolated from the fermentation products of Penicillium simplicissimum were shown to be insecticidal, yet the mechanism of their toxicity to insects remains unknown. We therefore examined the action of okaramine B on silkworm larval neurons using patch-clamp electrophysiology. Okaramine B induced inward currents which reversed close to the chloride equilibrium potential and were blocked by fipronil. Thus it was tested on the silkworm RDL (resistant-to-dieldrin) γ-aminobutyric-acid-gated chloride channel (GABACl) and a silkworm L-glutamate-gated chloride channel (GluCl) expressed in Xenopus laevis oocytes. Okaramine B activated GluCl, but not RDL. GluCl activation by okaramines correlated with their insecticidal activity, offering a solution to a long-standing enigma concerning their insecticidal actions. Also, unlike ivermectin, okaramine B was inactive at 10 μM on human α1β2γ2 GABACl and α1β glycine-gated chloride channels and provides a new lead for the development of safe insect control chemicals.

Phenylthiophenecarboxamide antagonists of the olfactory receptor co-receptor subunit from a mosquito.

Insects detect environmental chemicals using chemosensory receptors, such as the ORs, a family of odorant-gated ion channels. Insect ORs are multimeric complexes of unknown stoichiometry, formed by a common subunit (the odorant receptor co-receptor subunit, Orco) and one of many variable subunits that confer odorant specificity. The recent discovery of Orco directed ligands, including both agonists and antagonists, suggests Orco as a promising target for chemical control of insects. In addition to competitively inhibiting OR activation by Orco agonists, several Orco antagonists have been shown to act through a non-competitive mechanism to inhibit OR activation by odorants. We previously identified a series of Orco antagonists, including N-(4-ethylphenyl)-2-thiophenecarboxamide (OX1a, previously referred to as OLC20). Here, we explore the chemical space around the OX1a structure to identify more potent Orco antagonists. Cqui\\Orco+Cqui\\Or21, an OR from Culex quinquefasciatus (the Southern House Mosquito) that responds to 3-methylindole (skatole) and is thought to mediate oviposition behavior, was expressed in Xenopus oocytes and receptor function assayed by two-electrode voltage clamp electrophysiology. 22 structural analogs of OX1a were screened for antagonism of OR activation by an Orco agonist. By varying the moieties decorating the phenyl and thiophene rings, and altering the distance between the rings, we were able to identify antagonists with improved potency. Detailed examination of three of these compounds (N-mesityl-2-thiophenecarboxamide, N-(4-methylbenzyl)-2-thiophenecarboxamide and N-(2-ethylphenyl)-3-(2-thienyl)-2-propenamide) demonstrated competitive inhibition of receptor activation by an Orco agonist and non-competitive inhibition of receptor activation by an odorant. The ability to inhibit OR activation by odorants may be a general property of this class of Orco antagonist, suggesting that odorant mediated behaviors can be manipulated through Orco antagonism. The high conservation of Orco across insect species and previous demonstrations that various Orco ligands are active at ORs derived from several different insect orders suggests that Orco antagonists may have broad applicability.

Microbial Communities in Potato Roots and Soil in Organic and Integrated Production Systems Compared by the Plate Culturing Method

AbstractMicrobial communities in roots, rhizoplane, rhizosphere soil and non‐rhizosphere soil in potato were compared in organic and integrated production systems in 2005–2007. Identification of microorganisms was based on morphotyping. The density (number of colony‐forming units in a sample) of Fungi and Oomycota was significantly greater in the integrated system. Greater densities of Arthrobacter and Streptomyces occurred more often in organic and integrated systems, respectively. The dominant fungal taxa (with frequency &gt;5% in at least one habitat) included Aspergillus, Clonostachys + Gliocladium, Colletotrichum coccodes, Fusarium + Gibberella + Haematonectria + Neonectria, Gibellulopsis nigrescens, Paecilomyces, Penicillium, Phoma and Trichoderma. The subdominant taxa (with frequency 1–5%) included species from 16 genera. In the rhizoplane, rhizosphere and non‐rhizosphere soil, the total density of pathogens was greater in the organic system, and of antagonists in the integrated system. Dominant pathogens, that is, C. coccodes, Fusarium culmorum, Haematonectria haematococca and G. nigrescens, and dominant antagonists, that is, Clonostachys + Gliocladium and Trichoderma, occurred at greater density in the organic system. Subdominant pathogens, that is, Alternaria + Ulocladium, Pythium and Thanatephorus cucumeris, and subdominant antagonists, that is, Mortierella and Umbelopsis vinacea, occurred at significantly greater density in the integrated system. Incidence of sprout rot was more frequent in the organic system, and of Fusarium dry rot and black scurf in the integrated system. The organic system provided a less disease‐suppressive environment than the integrated system and resulted in smaller potato yield. An integrated system of potato production based on 4‐year rotation, white mustard as a cover crop, inorganic fertilizers including ammonium nitrate and chemical control of insects and diseases may be promoted in Poland.

INTEGRATION OF BIOLOGICAL MITE CONTROL AND CONVENTIONAL INSECT CONTROL IN STRAWBERRY

A 3-year project (2004-2006) aimed to improve integration of biological control of the strawberry tarsonemid mite (Phytonemus pallidus) and the normal plant protection practices in perennial outdoor strawberry production. Two chemicals, methiocarb and abamectin are available for strawberry tarsonemid mite control in Finland before flowering and after harvesting. In the meantime, only biological control is possible. Besides, pyrethroids and organophosphates are used to control insect pests, often just before flowering. The main obstacle to integrate biological control is the sensitivity of predatory mites to these insecticides, because long waiting periods needed to ensure the survival of predators may lead to far too late introductions of predators. Two species of predatory mites, Neoseiulus cucumeris and Neoseiulus barkeri were applied in strawberry fields using variable timing and waiting periods from the preceding insecticide treatments. Ca. 1-1.5 million predatory mites per ha were introduced once during the season. Monitoring of the mite situation was based on leaf samples which were collected 2-6 times during the seasons. The results showed that the integration of biological mite control and chemical control of insects is possible but requires more knowledge of the situation in the field than mere chemical control. Monitoring of pest insects may enable earlier timing of insecticide treatments and hence earlier introductions of predators. Insecticides with low persistence should be chosen if sprayings are delayed. Introductions of predators early enough when strawberry tarsonemid mite populations are still low are essential. Late season leaf sample inspections will support the decision making of possible complementary acaricide treatments after harvesting time.

Effects of biological and chemical insect control agents on fungal community structures in soil microcosms

In several European countries the entomopathogenic fungus Beauveria brongniartii is used for specifically controlling the European cockchafer, Melolontha melolontha, a pest in grassland and orchards. This biological control agent (BCA) is applied to soil, where it specifically infects the soil dwelling larvae of M. melolontha. Application of a fungal BCA to soil may potentially affect indigenous soil fungal populations. Therefore, it was the objective of this study to assess and compare such potential effects of the BCA to those of a carbofuran-based chemical control agent (CCA). The experimental system consisted of six soil microcosm treatments with and without larvae of M. melolontha and included BCA- and CCA-treatments. Microcosms were maintained under controlled conditions for 91 days and were sampled three times. Untreated larvae survived until the end of the experiment, whereas all treated larvae died within 28 days. Cultivation-independent quantification of B. brongniartii in soil was based on quantitative real-time PCR analysis of a specific simple-sequence-repeat marker and significantly correlated with cultivation-dependent quantification. Fungal ribosomal internal spacer analysis (RISA) revealed strongest and most significant changes in soil fungal communities for treatments that contained larvae that had died from either control agent. The BCA alone revealed much smaller and transient effects, while effects of the CCA were also small but significantly increased at the end of the experiment. The results revealed that either control strategy induced relatively small effects on soil fungal communities and that molecular genetic tools may be efficiently applied for monitoring and effect assessment of fungal BCAs.

Insect ryanodine receptors: molecular targets for novel pest control chemicals

Ryanodine receptors (RyRs) are a distinct class of ligand-gated calcium channels controlling the release of calcium from intracellular stores. They are located on the sarcoplasmic reticulum of muscle and the endoplasmic reticulum of neurons and many other cell types. Ryanodine, a plant alkaloid and an important ligand used to characterize and purify the receptor, has served as a natural botanical insecticide, but attempts to generate synthetic commercial analogues of ryanodine have proved unsuccessful. Recently two classes of synthetic chemicals have emerged resulting in commercial insecticides that target insect RyRs. The phthalic acid diamide class has yielded flubendiamide, the first synthetic ryanodine receptor insecticide to be commercialized. Shortly after the discovery of the phthalic diamides, the anthranilic diamides were discovered. This class has produced the insecticides Rynaxypyr and Cyazypyr. Here we review the structure and functions of insect RyRs and address the modes of action of phthalic acid diamides and anthranilic diamides on insect ryanodine receptors. Particularly intersting is the inherent selectivity both chemical classes exhibit for insect RyRs over their mammalian counterparts. The future prospects for RyRs as a commercially-validated target site for insect control chemicals are also considered.

Cuticular surface lipids are responsible for disguise properties of an entomoparasite against host cellular responses

Entomopathogenic nematodes are widely used as alternatives to chemicals for the biological control of insects. These endoparasites are symbiotically associated with bacteria that are lethal for the host; however, parasites need to overcome the host immune defences to complete a successful life cycle. The processes parasites employ to escape or depress host immunity are targeted at deceiving non-self recognition as well as inactivating defence reactions. The purpose of this paper is to investigate the interactions between the entomopathogenic nematode Steinernema feltiae and the lepidopteran Galleria mellonella, focusing on the role of the parasite's body-surface compounds in the immunoevasion of host cell-mediated responses. To evaluate host self/non-self discrimination and encapsulation efficiency, we carried out a series of interaction assays between cultured host hemocytes and parasites or isolated cuticles. The data obtained suggest that the parasite cuticular lipids (PCLs) are able to bind a variety of host hemolymph molecules; PCLs attract host proteins from the hemolymph creating a coat around the parasite, thus, enabling Steinernema to disguise itself against hemocytes recognition. The role of parasite lipids in the disguise process was also investigated by simulating the nematode body surface with agarose microbeads covered with purified cuticular components; when the beads were coated with cuticular lipids, host hemocytes were not able to recognize and encapsulate. Results suggest that by means of attracting host hemolymph components onto its cuticular surface, S. feltiae prevents hemocytes attachment to its cuticle and inhibits melanization by depleting hemolymph components.

Synthesis, 3D-QSAR, and docking studies of 1-phenyl-1 H-1,2,3-triazoles as selective antagonists for β3 over α1β2γ2 GABA receptors

A series of 16 1-phenyl-1 H-1,2,3-triazoles with substituents at both the 4- and 5-positions of the triazole ring were synthesized, and a total of 49 compounds, including previously reported 4- or 5-monosubstituted analogues, were examined for their ability to inhibit the specific binding of [ 3H]4′-ethynyl-4- n-propylbicycloorthobenzoate (EBOB), a non-competitive antagonist, to human homo-oligomeric β3 and hetero-oligomeric α1β2γ2 γ-aminobutyric acid (GABA) receptors. Among all tested compounds, the 4- n-propyl-5-chloromethyl analogue of 1-(2,6-dichloro-4-trifluoromethylphenyl)-1 H-1,2,3-triazole showed the highest level of affinity for both β3 and α1β2γ2 receptors, with K i values of 659 pM and 266 nM, respectively. Most of the tested compounds showed selectivity for β3 over α1β2γ2 receptors. Among all 1-phenyl-1 H-1,2,3-triazoles, the 4- n-propyl-5-ethyl analogue exhibited the highest (>1133-fold) selectivity, followed by the 4- n-propyl-5-methyl analogue of 1-(2,6-dibromo-4-trifluoromethylphenyl)-1 H-1,2,3-triazole with a >671-fold selectivity. The 2,6-dichloro plus 4-trifluoromethyl substitution pattern on the benzene ring was found to be important for the high affinity for both β3 and α1β2γ2 receptors. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) provided similar contour maps, revealing that an electronegative substituent at the 4-position of the benzene ring, a compact, hydrophobic substituent at the 4-position of the triazole ring, and a small, electronegative substituent at the 5-position of the triazole ring play significant roles for the high potency in β3 receptors. Molecular docking studies suggested that the putative binding sites for 1-phenyl-1 H-1,2,3-triazole antagonists are located in the channel-lining 2′-6′ region of the second transmembrane segment of β3 and α1β2γ2 receptors. A difference in the hydrophobic environment at the 2′ position might underlie the selectivity of 1-phenyl-1 H-1,2,3-triazoles for β3 over α1β2γ2 receptors. The compounds that had high affinity for β3 receptors with homology to insect GABA receptors showed insecticidal activity against houseflies with LD 50 values in the pmol/fly range. The information obtained in the present study should prove helpful for the discovery of selective insect control chemicals.

Molecular pharmacology of insect ion channels and implications for insect toxicology

Safe insecticides are essential if agriculture is to generate adequate supplies of high quality food, maintain the health of farm animals and ensure that human populations secure effective control of major disease vectors. Insect central and peripheral nervous systems contain important molecular targets of chemicals used to control insects. Insecticides with new modes of actions are under development, and several major new target molecules are emerging. Meanwhile, resistance to the current generation of insecticides continues to develop, restricting the long-term utility of these valuable chemicals. Also, methods for investigating the mechanisms of action, safety, and resistance are advancing at an accelerated pace. Modern insecticides offer improved selectivity for the target organism and understanding the mechanisms responsible may yield a future generation of effective control chemicals with reduced environmental impact. The 11th International Congress of Pesticide Chemistry (ICPC), which took place in Kobe, Japan from 6 to 11 August in 2006, chose this year as an opportune time to revisit current developments at the leading edge of research on the molecular pharmacology of ion channels targeted by insect control chemicals. This was the 2nd ICPC meeting to be held in Japan. An earlier symposium was held in Kyoto in 1982. Thus, two of us (Kazuhiko Matsuda of Kinki University, Nara and Yoshihisa Ozoe of Shimane University, Matsue) planned to invite world-leading scientists to Kinki University School of Agriculture (Fig. 1) for a satellite symposium entitled ‘‘Frontiers in Molecular Neurotoxicology’’ on August 4 prior to the start of ICPC 2006. The venue for the meeting, Kinki University School of Agriculture, is located about 6 miles west of the historical city of Nara. The city was built as the capital of Japan in 710 and still today contains many World Heritage sites, notably Todai-ji Temple, Kofukuji Temple, Kasuga-Taisha-Shrine, Gango-ji Temple, Yakushi-ji Temple, Toshodai-ji Temple, Nara Palace Site and Kasugayama Primeval Forest. Kinki University consists of 11 schools and 44 departments and was founded as the Osaka Technical College in 1925. The University started with the School of Engineering and the School of Commerce, both of which have grown to become the modern School of Business and Economics. Its strong links with Agriculture were developed in the second half of the twentieth century and the School of Agriculture was introduced in 1958. In 1989, the location of the School of Agriculture moved from Higashi Osaka to Nara. The aim of the 2006 symposium was to enhance our understanding of the current status and future perspectives in the field of molecular pharmacology of primarily insect ion channels. Authors have adopted various approaches, often in combination, and these K. Matsuda (&) Department of Applied Biological Chemistry, School of Agriculture, Kinki University, 3327-204, Nakamachi, Nara 631-8505, Japan e-mail: kmatsuda@nara.kindai.ac.jp

Non-target effects of a carbamate and the proteins avidin and aprotinin on in vitro development of a bacterial feeding nematode

A 24-well plate trial was conducted to determine the effects of conventional (oxamyl) and transgenic (avidin and aprotinin) insect control chemicals on the non-target bacterial-feeding nematode Bursilla sp. (Rhabditidae: Nematoda). Treatments were added to agar as pure oxamyl, avidin from egg whites or aprotinin from bovine lung, which was then inoculated with the bacteria Xanthamonas campestris as a food source for the nematodes. Oxamyl was toxic to the nematodes at a concentration of 400 ppm, significantly decreasing adult survival, egg laying and consequent progeny development and survival. The 400 ppm concentration of oxamyl also had a significant negative effect on bacterial growth in two of three experiments. Avidin is a biotin-binding protein and concentrations of 100 and 400 ppm significantly decreased the number of progeny produced by first generation nematodes through an effect on egg development. This effect was not significant ( P > 0.05 ) at either 10 or 25 ppm. This is the first report of avidin affecting nematode egg development and suggests a role for biotin in this process. Avidin had no effect on visual bacterial growth. Aprotinin is a protease inhibitor and concentrations up to 400 ppm had no significant effect on nematode development or bacterial growth. These lab-based findings need to be further investigated using plants producing avidin and aprotinin, growing in field soil in order to quantify their impact on environmental processes such as decomposition.