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Family pesticide use and childhood brain cancer.

The relationship between family pesticide use and childhood brain cancer was examined in a case-control study. Telephone interviews were conducted from June 1989 through March 1990 with the natural mothers of 45 childhood brain cancer cases, 85 friend controls, and 108 cancer controls. In comparisons to friend controls, significant positive associations were observed for use of pesticides to control nuisance pests in the home, no-pest-strips in the home, pesticides to control termites, Kwell shampoo, flea collars on pets, diazinon in the garden or orchard, and herbicides to control weeds in the yard. In comparisons to cancer controls, significant positive associations were observed for use of pesticide bombs in the home, pesticides to control termites, flea collars on pets, insecticides in the garden or orchard, carbaryl in the garden or orchard, and herbicides to control weeds in the yard. In general, positive associations in comparisons to one control group were supported by elevated odds ratios in comparisons to the other control group. Several potentially important associations were identified in this study. However, small sample sizes, potential recall bias, multiple comparisons, and lack of detailed exposure verification require further research to confirm these findings.

Brain Neoplasms↗

Insect-parasitic nematodes: from lab curiosities to model organisms.

Interest in studying insect-parasitic nematodes was originally focused on their potential as biological control agents of insects and other arthropod pests. Now, after 30 years of intense basic and applied research, realization of the practical use of insect-parasitic nematodes, particularly of entomopathogenic nematodes and their symbiotic bacteria, has spurred developments across a far broader scientific front. We are now entering a new era of discovery in which tools of molecular genetics are being increasingly used to address a range of biological questions. The knowledge gained from these efforts will directly benefit the practical application of insect-parasitic nematodes as more effective biopesticides. Moreover, these studies will advance these nematodes as unique and intrinsically interesting biological model systems not only for basic research but also in applied fields such as plant health, human medicine, pharmaceutical bioprospecting, and genetic engineering. In this review, the past and current state of insect-parasitic nematode research is summarized. Future research priorities and goals are identified and discussed.

Animals↗

Population structure of the beetle pests Phyllodecta vulgatissima and P. vitellinae on UK willow plantations.

Phyllodecta (= Phratora) vulgatissima and P. vitellinae (Coleoptera: Chrysomelidae) are important pests of willows and poplars. Their differences in host species preference may provide a non-chemical control strategy for pest control. However, little is known about population structure with respect to hosts, regions or seasons. Using five microsatellites, 850 P. vulgatissima and 1100 P. vitellinae individuals, comprising 17 and 22 UK samples, respectively, were genotyped. High diversity was observed at all loci. Migrant numbers exchanged per generation (Nm) were high (2.1-12.6 for P. vulgatissima and 0.9-12.2 for P. vitellinae), suggesting high genetic exchange between samples. Estimates of population differentiation (FST) and analyses of the data using Bayesian methods (Partition and Structure) showed little evidence of subdivision in relation to geography, sampling time or host.

Animals↗

Comparative effectiveness of an integrated pest management system and other control tactics for managing the spider mite Tetranychus ludeni (Acari: Tetranychidae) on eggplant.

The effect of an integrated pest management (IPM) package, host plant resistance, Chrysoperla carnea predation and neem oil were evaluated against the spider mite Tetranychus ludeni on eggplant (Solanum melongena L.) fields in 1996 and 1997, by estimating the mite population density and yield levels. Compared with the IPM package (Panruti local, C. carnea plus neem oil), the standard (susceptible) eggplant variety (MDU1) grown by farmers and treated with an acaricide (dicofol) had significantly higher mite densities. The predator C. carnea was recorded in significantly lower numbers in plots with the standard variety compared to a resistant variety (panruti local) with the full IPM package. Eggplant yield level and crop value were highest in the IPM-treated plots followed by Panruti local plus C. carnea. The standard variety treated with an acaricide had the lowest yield and value. These results indicated the usefulness of host plant resistance complemented by biorational control agents, such as C. carnea and neem oil, that these are suitable components in an IPM programme for managing the spider mite in endemic areas.

Animals↗

Lack of infection of vertebrate cells by the densovirus from the maize worm Mythimna loreyi (MlDNV).

Several densoviruses have been used successfully in biological control of pests in the tropics. The densovirus from Mythimna loreyi (MlDNV) could also be an important tool in biological control of important pests. However, safety concerns remain as previous reports suggested that densoviruses may infect and transform L cells (from mouse). In this study, we show using molecular-biology tools that neither L nor other vertebrate cells support replication or transcription of densovirus, either after infection or after transfection. Quantitative PCR indicated no increase of viral DNA due to replication in vertebrate cells, in contrast to that in insect LD652 cells. After transfection, both the NS and VP mRNAs could be detected in LD652 cells but not in L cells. Moreover, the viral genome was excised from the plasmid after transfection of the infectious clone in LD652 cells, indicative of viral NS protein production, in contrast to L cells. The viral genome was able to integrate in the host chromosome of L cells after transfection, but not after infection. However, no viral transcription could be detected after integration.

Animals↗

The ecology, evolution, and physiology of Cardinium: a widespread heritable endosymbiont of invertebrates.

Candidatus Cardinium hertigii (Cardinium) are maternally transmitted obligate intracellular bacteria found in a wide range of invertebrate hosts, including arthropods and nematodes. Infection with Cardinium has substantial consequences for host biology, with many strains manipulating host reproduction to favor symbiont transmission by (i) feminizing male hosts, (ii) altering host sex allocation, (iii) inducing parthenogenesis, or (iv) causing cytoplasmic incompatibility. Other Cardinium strains can confer benefits to their host or alter host behavior. Cardinium-modified host phenotypes can result in selective sweeps of cytological elements through host populations and potentially reinforce host speciation. Cardinium has potential for applications in controlling arthropod pest species and arthropod-vectored disease transmission, although much remains to be explored regarding Cardinium physiology and host interactions. In this review, we provide an overview of Cardinium evolution and host distribution. We describe the various host phenotypes associated with Cardinium and how biological and environmental factors influence these symbioses. We also provide an overview of Cardinium metabolism, physiology, and potential mechanisms for interactions with hosts based on recent studies using genomics and transcriptomics. Finally, we discuss new methodologies and directions for Cardinium research, including improving our understanding of Cardinium physiology, response to environmental stress, and potential for controlling arthropod pest populations.

Symbiosis↗

Beyond the spore--past and future developments of Bacillus thuringiensis as a biopesticide.

Formulated and sporulated cultures of Bacillus thuringiensis (Bt) are widely used as foliar sprays as part of integrated pest management strategies against insect pests of agricultural crops. Although in several cases the presence of the spore has been shown to improve the activity of the product, other Bt-based insecticides have been developed in which the spore is absent. The most notable of these are transgenic plants expressing just the insect toxin gene from the bacterium. This paper will discuss these developments, and the advantages and disadvantages of having the spore present.

Bacillus thuringiensis↗

The plcR regulon is involved in the opportunistic properties of Bacillus thuringiensis and Bacillus cereus in mice and insects.

Bacillus thuringiensis has been widely used for 40 years as a safe biopesticide for controlling agricultural pests and mosquitoes because it produces insecticidal crystal proteins. However, spores have also been shown to contribute to overall entomopathogenicity. Here, the opportunistic properties of acrystalliferous B. thuringiensis Cry(-) and Bacillus cereus strains were investigated in an insect species, Galleria mellonella, and in a mammal, BALB/c mice. In both animal models, the pathogenicity of the two bacterial species was similar. Mutant strains were constructed in which the plcR gene, encoding a pleiotropic regulator of extracellular factors, was disrupted. In larvae, co-ingestion of 10(6) spores of the parental strain with a sublethal concentration of Cry1C toxin caused 70% mortality whereas only 7% mortality was recorded if spores of the DeltaplcR mutant strain were used. In mice, nasal instillation of 10(8) spores of the parental strain caused 100% mortality whereas instillation with the same number of DeltaplcR strain spores caused much lower or no mortality. Similar effects were obtained if vegetative cells were used instead of spores. The cause of death is unknown and is unlikely to be due to actual growth of the bacteria in mice. The lesions caused by B. thuringiensis supernatant in infected mice suggested that haemolytic toxins were involved. The cytolytic properties of strains of B. thuringiensis and B. cereus, using sheep, horse and human erythrocytes and G. mellonella haemocytes, were therefore investigated. The level of cytolytic activity is highly reduced in DeltaplcR strains. Together, the results indicate that the pathogenicity of B. thuringiensis strain 407 and B. cereus strain ATCC 14579 is controlled by PlcR.

Animals↗

[The prescription of repellents].

Repellents are chemical products designed to ward off insects. They are effective against a wide range of arthropods including mosquitoes and flies but not against bees and wasps. Choosing the proper repellent can be difficult because no single product repels all pests. This article compares the performance and toxicity of various repellents based on reports describing systemic, topical, or physical repellents made from natural or synthetic ingredients. Essential oils are the most common natural ingredient. Synthetic ingredients range from dimethyphtalate, ethylexanediol, and diethyltoluamide (DEET) to new molecules such as 35/35, piperidine, bayerepel, and KBR 3023. Our findings indicate that DEET, used as the gold standard in most studies, is still the most effective repellent. There is no synergy between any of these products but combinations (e.g. ethylhexanediol and DEET) can optimize protection. In conclusion we propose guidelines for prescribing repellents to achieve the required level of protection in function of the duration of exposure and benefit-to-risk ratio. Several recommendations are made on the safe use repellents for adults and children.

Animals↗

Pest management in traditional maize stores in West Africa: a farmer's perspective.

Farmers in the Republic of Benin have few resources to invest in protection of stored maize, and prophylactic pesticide application is often recommended by extension and development agencies. Neither the efficacy nor profitability of such an application in traditional maize storage facilities has been addressed quantitatively. In this study, existing management options for stored maize were evaluated monthly over 6 mo in central and southern Benin with respect to their effects on grain injury and on densities of Prostephanus truncatus (Horn) and Sitophilus zeamais Motschulsky. P. truncatus infested 54% of the experimental stores in the study even though Teretrius nigrescens (Lewis), a natural enemy introduced against P. truncatus, was well established in the region. S. zeamais was the most common pest, found in 85% of the experimental storage facilities. Prophylactically treated maize was, on average, worth more than untreated maize for month 1 through 5 in southern Benin, after taking into account market price, pesticide costs, percentage grain damage and weight loss, but maize storage was not profitable overall. No difference was observed between treatments in central Benin. After 6 mo treated storage facilities were not significantly different from untreated storage facilities in terms of either percentage damage or profit in either region. A rapid scouting plan intended to provide farmers with a means for identifying storage facilities at greatest risk of severe P. truncatus infestation was field validated. Given that unsafe pesticide use is prevalent in Benin, research and extension services should clearly state the limitations to prophylactic treatment and increase the effort to educate farmers on appropriate pesticide use, store monitoring and marketing.

Animals↗

Potential of the Bacillus thuringiensis toxin reservoir for the control of Lobesia botrana (Lepidoptera: Tortricidae), a major pest of grape plants.

The potential of Bacillus thuringiensis Cry proteins to control the grape pest Lobesia botrana was explored by testing first-instar larvae with Cry proteins belonging to the Cry1, Cry2, and Cry9 groups selected for their documented activities against Lepidoptera. Cry9Ca, a toxin from B. thuringiensis, was the protein most toxic to L. botrana larvae, followed in decreasing order by Cry2Ab, Cry1Ab, Cry2Aa, and Cry1Ia7, with 50% lethal concentration values of 0.09, 0.1, 1.4, 3.2, and 8.5 microg/ml of diet, respectively. In contrast, Cry1Fa and Cry1JA were not active at the assayed concentration (100 microg/ml). In vitro binding and competition experiments showed that none of the toxins tested (Cry1Ia, Cry2Aa, Cry2Ab, and Cry9C) shared binding sites with Cry1Ab. We conclude that either Cry1Ia or Cry9C could be used in combination with Cry1Ab to control this pest, either as the active components of B. thuringiensis sprays or expressed together in transgenic plants.

Animals↗

Immunological control of ectoparasites: past achievements and future research priorities.

Recombinant vaccines are available for the control of the tick Boophilus microplus, while progress has been made in the development of vaccines against Lucilia cuprina and Chrysomya bezziana. Literature suggests that the control of other ectoparasites is feasible, either through the duplication in a vaccine of naturally acquired immunity or through 'concealed' antigen vaccines. Major deficiencies in our current knowledge however point to possible research opportunities for the future. The identification of protective antigens from all species is proceeding slowly, particularly for the antigens of naturally acquired immunity. Our capacity to produce effective recombinant antigens has progressed greatly, though there remains a major difficulty where some or all of the protective effect is due to immunogenic oligosaccharide. Our understanding of protective mechanisms is limited. The delivery of the appropriate immunological response remains difficult. Nevertheless, some of the most critical areas of ignorance are in basic biological issues: factors which affect the susceptibility of particular pest species to immunological attack and the implications of vaccine-induced effects for pest and disease control under field conditions. Increasingly too, effective pest control is likely to demand the integration of a variety of control technologies. The study of this integration is in its infancy.

Animals↗

Effects of combining the fungi Beauveria bassiana and Metarhizium anisopliae on the mortality of the tick Amblyomma variegatum (ixodidae) in relation to seasonal changes.

The effect of formulation, fungal concentration, type and seasonal changes on the mortality of the tick Amblyomma variegatum was investigated. A previous study demonstrated high pathogenicity of strains of the fungi Beauveria bassiana and Metarhizium anisopliae against the ticks Rhipicephalus appendiculatus and Amblyomma variegatum (Kaaya et al. J Invertebr Pathol 1996; 67: 15-20). The present study was undertaken to explore possible additive or synergistic effects of the two fungi on A. variegatum. The effects of oil and water formulations at different concentrations of each fungus and combination of the two on the mortality of A. variegatum in the laboratory and in the field during the wet and dry seasons were determined and compared. The oil formulation performed better in all assays, with highest tick mortality of 92% occurring during the wet season at conidia concentration of 1 x 10(10) conidia/ml of the mixed fungi compared to 49% for the water formulation at similar conidia concentration. However, at the same conidial concentration during the dry season, mortalities in the field were relatively low with the mixture of the fungi recording 24% and 17% tick mortality for the oil and water formulation respectively. The effect of infecting the ticks with a cocktail of the two fungi was inconclusive under more controlled conditions in the laboratory but field results under both wet and dry seasons indicated significant differences between the separate and mixed fungi infections. The results demonstrate a potential of cocktail formulations in the control of ticks and possibly of other arthropod pests.

Animals↗