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At least 235 records · Page 13Linked to original sources
PubMed2005

Microsatellites and 16S sequences corroborate phenotypic evidence of trans-Andean variation in the parasitoid Microctonus hyperodae (Hymenoptera: Braconidae).

Eight South American geographical populations of the parasitoid Microctonus hyperodae Loan were collected in South America (Argentina, Brazil, Chile and Uruguay) and released in New Zealand for biological control of the weevil Listronotus bonariensis (Kuschel), a pest of pasture grasses and cereals. DNA sequencing (16S, COI, 28S, ITS1, beta-tubulin), RAPD, AFLP, microsatellite, SSCP and RFLP analyses were used to seek markers for discriminating between the South American populations. All of the South American populations were more homogeneous than expected. However, variation in microsatellites and 16S gene sequences corroborated morphological, allozyme and other phenotypic evidence of trans-Andes variation between the populations. The Chilean populations were the most genetically variable, while the variation present on the eastern side of the Andes mountains was a subset of that observed in Chile.

Animals↗
PubMed1999

Experimental formulations of Bacillus sphaericus and B. thuringiensis israelensis against Culex quinquefasciatus and Anopheles gambiae (Diptera: Culicidae) in Burkina Faso.

Efficacies of locally produced, sustained release granular formulations of Bacillus sphaericus (BS) strain 2362 and B. thuringiensis israelensis (BTI) were compared with commercial liquid concentrates of the same bacteria in cesspits and rain-filled puddles in Ouagadougou, Burkina Faso. Duration of control was dependent on the product, the transient nature of some sites, and the target mosquito larvae. BS granules applied at the rate of 3.0 g/m2 (30 kg/ha) reduced Culex quinquefasciatus Say 99% for at least 28 d in cesspits, whereas the same dosage of 2 BTI granules and commercial liquid formulations of BS and BTI gave 95% control for 8-14 d. The levels of control obtained with the 2 liquid products were not different. Accordingly, the reported inferiority of BTI to BS in polluted water was attributed to low dosages of BTI. Because products were compared at equal application rates, recycling seemed to play a minor role compared with product formulation. BTI was more broad spectrumed than BS also killing Cx decens Theobald, Cx cinereus Granpré & Charmoy, and psychodid larvae. Depending on the method of estimation, granular and liquid BS gave 60-97% control of Anopheles gambiae s.l. Giles for 10 d in rain puddles. The transient nature of the rain puddles was probably more important for the duration of control than formulation type. Cesspits and puddles, respectively, were the most important larval habitats for these 2 species in Ouagadougou during the rainy season, and these trials showed that An. gambiae was not controlled easily with larvicides alone. However, biological larvicides may play a central role in the control of Cx. quinquefasciatus provided that most breeding sites are treated.

Animals↗
PubMed2003

Biocontrol of Bacillus subtilis against infection of Arabidopsis roots by Pseudomonas syringae is facilitated by biofilm formation and surfactin production.

Relatively little is known about the exact mechanisms used by Bacillus subtilis in its behavior as a biocontrol agent on plants. Here, we report the development of a sensitive plant infection model demonstrating that the bacterial pathogen Pseudomonas syringae pv tomato DC3000 is capable of infecting Arabidopsis roots both in vitro and in soil. Using this infection model, we demonstrated the biocontrol ability of a wild-type B. subtilis strain 6051 against P. syringae. Arabidopsis root surfaces treated with B. subtilis were analyzed with confocal scanning laser microscopy to reveal a three-dimensional B. subtilis biofilm. It is known that formation of biofilms by B. subtilis is a complex process that includes secretion of surfactin, a lipopeptide antimicrobial agent. To determine the role of surfactin in biocontrol by B. subtilis, we tested a mutant strain, M1, with a deletion in a surfactin synthase gene and, thus, deficient in surfactin production. B. subtilis M1 was ineffective as a biocontrol agent against P. syringae infectivity in Arabidopsis and also failed to form robust biofilms on either roots or inert surfaces. The antibacterial activity of surfactin against P. syringae was determined in both broth and agar cultures and also by live-dead staining methods. Although the minimum inhibitory concentrations determined were relatively high (25 microg mL(-1)), the levels of the lipopeptide in roots colonized by B. subtilis are likely to be sufficient to kill P. syringae. Our results collectively indicate that upon root colonization, B. subtilis 6051 forms a stable, extensive biofilm and secretes surfactin, which act together to protect plants against attack by pathogenic bacteria.

Agar↗
PubMed2001

Source-sink dynamics between transgenic and non-transgenic habitats and their role in the evolution of resistance.

The interaction of population dynamics and movement among two habitat types (toxic transgenic fields and nontoxic refuge fields) on the evolution of insecticide resistance was examined in two different simulation models. The two models were developed to test the hypothesis that increasing habitat grain from fine-grained to coarse-grained, and the resultant increase in nonrandom mating, would increase the rate of local adaptation, here the evolution of resistance. The first model, a complex, stochastic spatially explicit model, altered habitat grain by varying adult dispersal rates between habitat patches. In contrast to the expectation that increasing patch isolation and increasing the coarseness of the habitats would increase the rate of resistance evolution, intermediate levels of dispersal actually delayed resistance by as much as fivefold over the range of dispersal levels observed. Source-sink dynamics related to ovipositional patterns and the related population dynamics appear to explain the results. A simple deterministic model was developed to abstract out the separate impacts of mating and ovipositional behaviors. This model showed qualitatively the same results, although under similar assumptions it predicted much longer delays in resistance evolution. In this model, nonrandom mating alone always increased the rate at which insects adapted to transgenic crops, but nonrandom mating in combination with nonrandom oviposition could significantly delay resistance evolution. Differences between the two models may be due to the population regulation incorporated in the spatially explicit model. The models clearly suggest that resistance management programs using untreated refuges should not over-emphasize random mating at the cost of making the habitat too fine-grained.

Animals↗
PubMed2002

Risk assessment for release of genetically modified organisms: a virus to reduce the fertility of introduced wild mice, Mus domesticus.

Risk assessment is a key task in developing genetically modified organisms (GMOs) intended for release into the environment. A risk assessment protocol is described, focusing on genetically modified biological control agents intended to reduce fertility in mammalian pests. The protocol is being applied to development of an immunocontraceptive murine cytomegalovirus vaccine intended to reduce the frequency and extent of costly troublesome plagues of introduced house mice, Mus domesticus, in southern Australia. Success of the agent, including regulatory approval for release to target populations, will depend on demonstrated biosafety, on the biophysical consequences of releasing the agent, and on public perceptions of the consequences and ongoing risks. The proposed risk assessment protocol addresses biosafety and the biophysical and social risks. It elicits perceptions of interaction and risk from the project scientists and from representatives of interested or affected sectors of society. The perceptions are documented for examination interactively in subsequent socially inclusive formal risk assessments. Representatives of the relevant social sectors participate with the scientists, iteratively if needed, in a workshop to assess the risks of releasing the particular GMO into the environment, using a formal inductive procedure, GENHAZ, designed specifically for assessment and management of the risks of GMOs. Use of this protocol is intended to precede and complement risk assessment and risk management procedures specified by gene technology legislation and regulations.

Animals↗
PubMed1987

Floating bait formulations increase effectiveness of Bacillus thuringiensis var. israelensis against Anopheles larvae.

The development and screening of floating-type bait formulations designed to improve the activity of bacterial toxins against larval Anopheles is described. Floating and spreading abilities of carrier particles (wheat flour) were compared using corn oil, lecithin, and two products yielding surface films on water (Arosurf and Liparol). Mixtures containing 1 or 5% Arosurf showed the best spreading abilities on a water surface, but strongly inhibited the ingestion of wheat flour by Anopheles albimanus larvae. Corn oil and lecithin improved spreading satisfactorily at a concentration of 5% and inhibited larval feeding by only 6-25%. To select a suitable concentration of active ingredient in formulations, Bacillus thuringiensis var. israelensis (B.t.i.) primary powder in concentrations ranging from 0.01 to 0.5% was mixed with wheat flour/corn oil mixtures and tested in quantities exceeding the gut volumes of treated larvae. Complete mortality was obtained with concentrations of 0.1% (Anopheles stephensi), 0.2% (An. albimanus), or 0.3% (An. quadrimaculatus) B.t.i. When in 175-liter containers the activity of formulations (5% corn oil, 0.2% B.t.i.) and of toxin suspensions was compared by conventional dosage-mortality regression, formulations were more active by a factor of 68 against An. stephensi, 39 against An. albimanus and 67 against An. quadrimaculatus.

Animals↗
PubMed1998

Laboratory bioassay to compare susceptibilities of Aedes aegypti and Anopheles albimanus to Bacillus thuringiensis var. israelensis as affected by their feeding rates.

This study presents the effect of differences in the feeding rates of Aedes aegypti and Anopheles albimanus on their susceptibilities to Bacillus thuringiensis israelensis. Aedes aegypti was more susceptible than An. albimanus because of its faster rate of feeding. Aedes aegypti ingested 11.5 times more spores than did An. albimanus, resulting in lower LT50 values. Anopheles albimanus larvae fed at a slower rate and required fewer spores than Ae. aegypti to induce 50% mortality. These findings support earlier reports of much higher concentrations of B. thuringiensis required to kill various anopheline species.

Aedes↗
PubMedDate not supplied

[Mermithids as biological control agents of blackflies].

About 80 species of mermithids parasitic in blackflies have been recorded from the Ethiopian and Holarctic regions. Species of three genera, Mesomermis, Gastromermis and Isomermis, are most common parasites of blackflies. Critical periods during the ontogenesis of all mermithids are associated with the penetration of infective larvae into the host and protective reactions of the later. Intraspecific hybridization of the parasites is recommended in order to increase the effectiveness of mermithids as agents of biological control of blackflies.

Animals↗
PubMed2005

Monoclonal antibodies reveal the potential of the tetragnathid spider Pachygnatha degeeri (Araneae: Tetragnathidae) as an aphid predator.

The drive towards a more sustainable and integrated approach to pest management has engendered a renewed interest in conservation biological control, the role of natural enemy communities and their interactions with prey. Monoclonal antibodies have provided significant advances in enhancing our knowledge of trophic interactions and can be employed to help quantify predation on target species. The tetragnathid spider Pachygnatha degeeri Sundevall was collected from fields of winter wheat in the UK and assayed by ELISA for aphid proteins. It was demonstrated that this spider did not simply consume greater quantities of aphids because it was bigger. In addition, P. degeeri contained significantly greater concentrations of aphid in their guts than other spiders, showing that aphids comprised a greater proportion of their diet. Although P. degeeri constituted only 6% of the spider population numerically, females and males respectively contained 16% and 37% of total aphid proteins within all spiders screened, significantly more than their density would predict. These spiders also preyed upon aphids at a disproportionately high rate in June, during the aphid establishment phase, theoretically the best time for limiting growth in the aphid population. Although less abundant than other generalist predators, the capability of these hunting spiders to consume large numbers of aphids highlights them as a more significant component of the predator complex than had previously been realized. Limitation of aphid numbers early in the year by generalist predators provides more time for the specialist aphid predators and parasitoids to move in.

Analysis of Variance↗
PubMed2001

Assessment of toxic potential of local Jordanian Bacillus thuringiensis strains on Drosophila melanogaster and Culex sp. (Diptera).

AIMS: To assess the toxic potential of different local Jordanian Bacillus thuringiensis isolates on larvae of Drosophila melanogaster and Culex sp. METHODS AND RESULTS: Scanning electron microscopy revealed the presence of spherical, bi-pyramidal, and bi-pyramidal and cuboidal parasporal bodies produced by the toxic isolates. Spherical inclusions dominated. The toxicity of the isolates to the two insects, determined using 24-well plates or vials, indicated that the 50% lethal concentration (LC50) of the bacterial suspension for D. melanogaster and Culex sp. larvae varied from 4.60 to 8.65, and from 5.30 to 6.74, respectively. CONCLUSION: Comparison of the LC50 values of isolate 82 with those of the reference strain B. t. israelensis showed that this isolate has a higher toxicity potential. SIGNIFICANCE AND IMPACT OF THE STUDY: Some local Jordanian B. thuringiensis isolates exhibit toxic potential that could be used to control some important pests, and could replace chemical pesticides.

Animals↗
PubMed2004

The gut bacteria of insects: nonpathogenic interactions.

The diversity of the Insecta is reflected in the large and varied microbial communities inhabiting the gut. Studies, particularly with termites and cockroaches, have focused on the nutritional contributions of gut bacteria in insects living on suboptimal diets. The indigenous gut bacteria, however, also play a role in withstanding the colonization of the gut by non-indigenous species including pathogens. Gut bacterial consortia adapt by the transfer of plasmids and transconjugation between bacterial strains, and some insect species provide ideal conditions for bacterial conjugation, which suggests that the gut is a "hot spot" for gene transfer. Genomic analysis provides new avenues for the study of the gut microbial community and will reveal the molecular foundations of the relationships between the insect and its microbiome. In this review the intestinal bacteria is discussed in the context of developing our understanding of symbiotic relationships, of multitrophic interactions between insects and plant or animal host, and in developing new strategies for controlling insect pests.

Animals↗
PubMed1998

Pathogenic action of Penicillium species on mosquito vectors of human tropical diseases.

In vitro bioassays were performed in order to assess the pathogenicity of 13 Penicillium strains in 2nd stage larvae of Aedes aegypti, Aedes fluviatilis, Anopheles aquasalis and Culex quinquefasciatus. Mortality rates began in the first 24 hours, ranging from 0 to 100%. P. corylophilum, P. fellutanum, P. implicatum, P. janthinellum, P. viridicatum and P. waksmanii species tested on Aedes aegypti larvae and at different concentrations presented mortality rates from 0 to 6.6%. These species, when tested on Aedes fluviatilis, Anopheles aquasalis and Culex quinquefasciatus larvae, presented a mortality rate of 3.33% to 100%. Susceptibility of Aedes fluviatilis, Aedes aegypti, Anopheles aquasalis and Culex quinquefasciatus mosquitoes to the tested agents, turn P. corylophilum and P. janthinellum into candidates for potential use in biological control of vectors.

Animals↗
PubMed2002

A transgene-based, embryo-specific lethality system for insect pest management.

Biological approaches to insect pest management offer alternatives to pesticidal control. In area-wide control programs that cover entire regions, the sterile insect technique (SIT) can be used to successfully suppress economically important pest species by the mass release of sterilized pest organisms. However, conventional sterilization by ionizing radiation reduces insect fitness, which can result in reduced competitiveness of the sterilized insects. Here we report a transgene-based, dominant embryonic lethality system that allows for generation of large quantities of competitive but sterile insects without the need of irradiation. The system involves the ectopic expression of a hyperactive pro-apoptotic gene that causes embryo-specific lethality when driven by the tetracycline-controlled transactivator (tTA) under the regulation of a cellularization gene enhancer-promoter. We have successfully tested this system in Drosophila melanogaster. The embryonic lethality can be suppressed maternally, which will allow it to be combined with transgenic female-specific lethality systems to raise only vigorous but sterile males.

Animals↗
PubMed2005

IgE-sensitization to predatory mites and respiratory symptoms in Swedish greenhouse workers.

BACKGROUND: Predatory mites are used as biological pesticides worldwide for control of spider mites and other pests in greenhouses. The aim of this study was to evaluate the impact of occupational exposure to Phytoseiulus persimilis and Hypoaspis miles on IgE sensitization among a large group of Swedish greenhouse workers and to examine the relationship between exposure and allergic asthma and rhinoconjunctivitis. METHODS: A total of 96 greenhouse workers from the southern part of Sweden, who were using the predatory mites for control of pests, were investigated with a questionnaire and a medical examination including lung function test. Blood samples were taken to test for allergen-specific IgE antibodies to Phytoseiulus persimilis and Hypoaspis miles as well as to Tetranychus urticae, Dermatophagoides pteronyssinus/farinae and Tyrophagus putrescentiae. RESULTS: Seventeen of the 96 workers were positive in ImmunoCAP to predatory mites: 17 to P. persimilis (17.7%) and 14 to H. miles (14.6%). Subjects sensitized to predatory mites were significantly more often atopic (13/17), defined as a positive Phadiatop, than those who lacked IgE against these mite species (17/79) (P <0.01). IgE antibodies to the red spider mite T. urticae were present among 23 subjects. Thirty-five of the investigated subjects displayed a positive ImmunoCAP to at least one of the investigated mite species. Furthermore, sensitization to any of the mites tested was significantly associated with asthma (OR=9.3) and rhinoconjunctivitis (OR=4.3). CONCLUSIONS: IgE sensitization to predatory mites, P. persimilis and H. miles, is common among greenhouse workers. The findings stress the importance of improved allergen avoidance in greenhouse environments.

Adult↗