Tool For Biological Control Research Articles

Quorum quenching is an antivirulence strategy employed by endophytic bacteria

Bacteria predominantly use quorum sensing to regulate a plethora of physiological activities such as cell-cell crosstalk, mutualism, virulence, competence, biofilm formation, and antibiotic resistance. In this study, we investigated how certain potent endophytic bacteria harbored in Cannabis sativa L. plants use quorum quenching as an antivirulence strategy to disrupt the cell-to-cell quorum sensing signals in the biosensor strain, Chromobacterium violaceum. We used a combination of high-performance liquid chromatography high-resolution mass spectrometry (HPLC-ESI-HRMS(n)) and matrix-assisted laser desorption ionization imaging high-resolution mass spectrometry (MALDI-imaging-HRMS) to first quantify and visualize the spatial distribution of the quorum sensing molecules in the biosensor strain, C. violaceum. We then showed, both quantitatively and visually in high spatial resolution, how selected endophytic bacteria of C. sativa can selectively and differentially quench the quorum sensing molecules of C. violaceum. This study provides fundamental insights into the antivirulence strategies used by endophytes in order to survive in their ecological niches. Such defense mechanisms are evolved in order to thwart the plethora of pathogens invading associated host plants in a manner that prevents the pathogens from developing resistance against the plant/endophyte bioactive secondary metabolites. This work also provides evidence towards utilizing endophytes as tools for biological control of bacterial phytopathogens. In continuation, such insights would even afford new concepts and strategies in the future for combating drug resistant bacteria by quorum-inhibiting clinical therapies.

Regulatory experience and challenges for the release of GM insects

Genetically modified (GM) insects are a potentially valuable new tool for the biological control of insect pests of humans, animals and plants. Considerable progress has been made recently in transfer of GM insects from the laboratory to release and evaluation in the environment. As with other new genetic technologies, regulatory agencies have often found it challenging to determine the regulatory regime under which they should be evaluated, and have either adapted existing regulatory frameworks or adopted new ones. No country has legislation specifically for GM insects. However, irrespective of the regulatory regime under which they are evaluated, the purpose of their regulation remains the same; to protect human health and the environment. Consequently there are evaluation themes common to their regulatory scrutiny, which are elucidated here. There have also been some challenges and issues encountered during the risk evaluation for field release of GM insects, and this paper will highlight some of these to assist others when considering policy, regulation and assessment of GM insects. Useful regulatory and policy precedents also exist from the regulation of biological control agents and the global protection of plants from pests under the International Standards for Phytosanitary Measures (ISPM) framework. Where countries do not have existing regulations, these evaluation instruments could have the potential to be adapted to form a suitable framework for the assessment of risk for GM insects. Finally, some considerations for future policy and regulation in this area are discussed.

Metabolic patterns of bacterial communities in aerobic compost teas associated with potential biocontrol of soilborne plant diseases

Aerated compost teas (ACTs) are organic products obtained by forced aeration of composts suspended in liquid phase. These products may be biological control tools alternative to synthetic fungicides, because ACTs contain antagonistic microorganisms. In this study, soilborne disease suppressive ability of seven water ACTs, extracted from five horticultural residue-based composts, from an animal waste anaerobic solid digestate and from a commercial municipal waste compost, was assessed using in vitro and in vivo systems. All the ACTs inhibited in vitro growth of Verticillium dahliae , Fusarium oxysporum f. sp. lycopersici , Rhizoctonia solani , Sclerotinia minor , Sclerotium rolfsii and Botrytis cinerea . Filter or thermal sterilization eliminated in vitro suppression, suggesting that microorganisms play key roles in pathogen inhibition. Drenching applications of raw ACTs have potential to reduced disease symptoms caused by R. solani on savoy cabbage, S. minor on lettuce and S. rolfsii on pepper, improved the biomass production and did not show any sign of phytotoxicity. Both in vitro and in vivo suppressiveness of ACTs may be explained by antagonistic bacterial communities that provide general suppression activities. The metabolic BIOLOG GN and GP profiles reflected the functional potential of the numerically dominant members of the microbial communities used as inoculum. This study has demonstrated that useful resident microorganisms, including mainly Gram-positive and Gram-negative antagonistic bacteria, are likely to be responsible for biological control activity of ACTs.

Foraging activity of the social wasp Polybia emaciata (Hymenoptera: Vespidae: Polistinae)

To characterize foraging activity of the social wasp Polybia emaciata nests were installed in three commercial monocultures (4 nests/culture) in the Colombian Caribbean Region. Observations were made for 36 days between 06:00 and 18:30 hours, with an average of 20 hours of observation per nest and 80 hours per crop. Foragers returned with liquid in 53.2% of the cases, with solid prey in 27.2%, and with building materials in 9.1%; the remaining 11.4% did not carry identifiable loads. The solid diet included prey from the orders Diptera (32.2%), Coleoptera (31%), Hemiptera (13.4%), Lepidoptera (8.8%), Hymenoptera (5.4), Neuroptera (0.8%), Orthoptera (1.1%), Araneae (1.9%), and Isopoda (0.4%); the remaining 5% was no identifiable. Adult insects from families Tephritidae, Chrysomelidae and Lonchaeidae were the most common prey. High temperatures and low relative humidity positively influenced foraging activity. A projection of the data suggests that a nest of P. emaciata may receive 78 prey per day. These results allows quantitative estimates for the use of P. emaciata as an alternative biological control tool for agroecosystems in this region.

In vitro investigations on the biological control of Xiphinema index with Trichoderma species

Abstract The application of Trichoderma spp. for the suppression of plant-parasitic nematode populations is a promising tool in biological control. Sixteen strains of six Trichoderma species (T. atroviride, T. harzianum, T. rossicum, T. tomentosum, T. virens and T. asperellum) were tested in vitro in order to identify the most appropriate strains to control the dagger nematode Xiphinema index. Mortality assays revealed that the strains of the widely investigated T. harzianum species have caused significant reduction of X. index populations, although T. harzianum strains were not the most efficient among all the tested fungi. Certain T. virens and T. atroviride strains and T. rossicum have triggered faster and higher mortality. Generally, our data indicate that Trichoderma species have innate ability to decrease X. index population. Furthermore, as we had difficulties with maintaining X. index in vitro, we successfully used a newly developed method to keep X. index specimens viable during the experiments.

Impact of environmental factors on mosquito dispersal in the prospect of sterile insect technique control

The aim of this paper is to develop a mathematical model to simulate mosquito dispersal and its control taking into account environmental parameters, like wind, temperature, or landscape elements. We particularly focus on the Aedes albopictus mosquito which is now recognized as a major vector of human arboviruses, like chikungunya, dengue, or yellow fever. One way to prevent those epidemics is to control the vector population. Biological control tools, like the Sterile Insect Technique (SIT), are of great interest as an alternative to chemical control tools which are very detrimental to the environment. The success of SIT is based not only on a good knowledge of the biology of the insect, but also on an accurate modeling of the insect’s distribution. We consider a compartmental approach and derive temporal and spatio-temporal models, using Advection–Diffusion–Reaction equations to model mosquito dispersal. Periodic releases of sterilized males are modeled with an impulse differential equation. Finally, using the splitting operator approach, and well-suited numerical methods for each operator, we provide numerical simulations for mosquito spreading, and test different vector control scenarios. We show that environmental parameters, like vegetation, can have a strong influence on mosquito distribution and in the efficiency of vector control tools, like SIT.

A Semiautomatic Cell Counting Tool for Quantitative Imaging of Tissue Engineering Scaffolds

Automatic image analysis algorithms are in general dedicated quantification tools used for very specific types of microscopic cell images, but are not robust enough to accurately quantify the cell number and distribution in the wide variety for fluorescence images that exist in the field of tissue engineering (TE) today, where cell-material (scaffold) interactions are being evaluated more and more. In this study, a semiautomatic algorithm was developed that allows the user to manually count a limited part of a TE scaffold image, and then automatically counts the cells of the full image based on that calibration dataset. The algorithm was validated on images of cells on a two-dimensional (2D) titanium (Ti) substrate, in a three-dimensional (3D) Ti scaffold and in a fibrin hydrogel by comparison with manual cell counting and with an indirect cell counting using metabolic assay. The average relative error between this semiautomatic and the manual approach was 3.4% for the 2D Ti substrates, 5.9% for the 3D Ti scaffolds, and 14.1% for the fibrin hydrogels. Hereby a proof of concept was delivered that could lead to an increased use of automated cell imaging as a reliable 2D and 3D quantitative tool for both basic biological research and process control of clinical TE products.

Modeling and Simulations of Mosquito Dispersal. The Case of Aedes albopictus

To prevent epidemics of mosquito-transmitted diseases like Chikungunya in RВґeunion Island, we develop tools to control its principal vector, Aedes albopictus. Biological control tools, like the Sterile Insect Technique (SIT), are of great interest as an alternative to chemical control tools which are very detrimental to environment. The success of SIT is based on a good knowlege of the biology of the insect, but also on an accurate modeling of the insects distribution. We model the mosquito dispersal with a system of coupled parabolic PDEs. Considering vector control scenarii, we show that the environment can have a strong influence on mosquito distribution and in the efficiency of vector control tools.

The biological control of the malaria vector.

The call for malaria control, over the last century, marked a new epoch in the history of this disease. Many control strategies targeting either the Plasmodium parasite or the Anopheles vector were shown to be effective. Yet, the emergence of drug resistant parasites and insecticide resistant mosquito strains, along with numerous health, environmental, and ecological side effects of many chemical agents, highlighted the need to develop alternative tools that either complement or substitute conventional malaria control approaches. The use of biological means is considered a fundamental part of the recently launched malaria eradication program and has so far shown promising results, although this approach is still in its infancy. This review presents an overview of the most promising biological control tools for malaria eradication, namely fungi, bacteria, larvivorous fish, parasites, viruses and nematodes.

Biological control of trichostrongyles in beef cattle by the nematophagous fungus Duddingtonia flagrans in tropical southeastern Brazil

The efficacy of a fungal formulation based on the nematophagous fungus Duddingtonia flagrans was assessed in the control of cattle trichostrongyles. Twenty male Nellore calves, six-month-old, divided in two groups (fungus-treated and control without fungus) were fed on a pasture of Brachiaria decumbens naturally infected with larvae of bovine trichostrongyles. Animals of the treated group received doses of sodium alginate mycelial pellets orally (1g/10kg live weight, twice a week), for 12months. Feces samples were collected for egg count (eggs per gram of feces–EPG) and coprocultures during 12months. There was a significant reduction in EPG (56.7%) and infective larvae (L3) in coprocultures (60.5%) for animals of the treated group in relation to the control group at the end of the study. There was a significant reduction of L3 (64.5%) in herbage samples collected up to 0–20cm from fecal pats and 73.2% in distant samples (20–40cm) between the fungus-treated group and the control group. The treatment with sodium alginate pellets containing the nematode trapping fungus D. flagrans reduced trichostrongylid in tropical southeastern Brazil and could be an effective tool for biological control of this parasitic nematode in beef cattle.

A Semiochemical Slow-release Formulation in a Biological Control Approach to Attract Hoverflies

E-β-Farnesene, the alarm pheromone of many aphid species, and E-β-caryophyllene are considered as two sesquiterpenes attractive for aphid predators, among which Syrphidae species. Both compounds were formulated in alginate gel beads as slow-release devices in a biological control approach against aphids. Semiochemical diffusion from beads was studied in the laboratory according to abiotic parameters. Efficiency of formulations as hoverfly attractant was demonstrated in field experiments from June to August 2009. The diffusion of semiochemicals from alginate bead formulations was principally limited by high values (>85%) of relative humidity in the air. Temperature also impacts the release of volatile compounds. In field experiments, these two abiotic factors were supposed to highly condition the trapping of hoverflies. These field trappings demonstrated the efficiency of both semiochemical formulations compared to control (formulation without semiochemical) to catch females of Syrphidae during three months. This research proved the efficiency of semiochemical alginate formulations as potential biological control tool to attract aphid predators.

Wolbachia infection in Trissolcus species (Hymenoptera: Scelionidae)

Wolbachia is a maternally transmitted intracellular symbiont which causes reproductive distortions in the arthropods it infects. In recent years there has been an increasing interest in using Wolbachia as a potential tool for biological control by genetic manipulation of insect pests. In the present paper we report Wolbachia infection in several Trissolcus wasps (Hymenoptera: Scelionidae) which are important egg parasitoids of the sunn pest, Eurygaster integriceps Puton (Heteroptera: Scutellaridae). We used DNA sequence data for a gene encoding a surface protein of Wolbachia (wsp) not only to confirm Wolbachia infection but also to discriminate Wolbachia strains. Phylogenetic analyses indicated that Wolbachia strains in Trissolcus species were closely related to one another and belonged to supergroup B. Determination of the infection status of various populations, the possible role of Wolbachia in causing the incompatibility and knowledge of the reproductive compatibility of Trissolcus populations is important for the success of parasitoids in sunn pest management.

Detection and Characterization of Wolbachia Infections in Natural Populations of Aphids: Is the Hidden Diversity Fully Unraveled?

Aphids are a serious threat to agriculture, despite being a rather small group of insects. The about 4,000 species worldwide engage in highly interesting and complex relationships with their microbial fauna. One of the key symbionts in arthropods is Wolbachia, an α-Proteobacterium implicated in many important biological processes and believed to be a potential tool for biological control. Aphids were thought not to harbour Wolbachia; however, current data suggest that its presence in aphids has been missed, probably due to the low titre of the infection and/or to the high divergence of the Wolbachia strains of aphids. The goal of the present study is to map the Wolbachia infection status of natural aphids populations, along with the characterization of the detected Wolbachia strains. Out of 425 samples from Spain, Portugal, Greece, Israel and Iran, 37 were found to be infected. Our results, based mainly on 16S rRNA gene sequencing, indicate the presence of two new Wolbachia supergroups prevailing in aphids, along with some strains belonging either to supergroup B or to supergroup A.

Endosymbiotic Wolbachia bacteria as biological control tools of disease vectors and pests

Wolbachia bacteria are common cytoplasmic symbionts of insects, mites and filarial nematodes. They can alter the reproduction of their hosts. The symbiont could be eliminated, transferred or used through genetic alteration to take advantage or remove their possible influences on pests and/or natural enemies. Their extensive effects on reproduction and host fitness have made Wolbachia the subject of growing attention as a potential biocontrol agent. Here, we summarize the relations of Wolbachia in the control of disease vectors and pests. Furthermore, the drawbacks of these bacteria are also discussed.

Using consumption rate to assess potential predators for biological control of white perch

Key-words: biological control, predation, consumption rate, white perch, Morone americana Control of undesirable fishes is important in aquatic systems, and using predation as a tool for biological control is an attractive option to fishery biologists. However, determining the appropriate predators for biological control is critical for success. The objective of this study was to evaluate the utility of consumption rate as an index to determine the most effective predators for biological control of an invasive fish. Consumption rate values were calculated for nine potential predators that prey on white perch Morone americana in Branched Oak and Pawnee reservoirs, Nebraska. The consumption rate index provided a unique and insightful means of determining the potential effectiveness of each predator species in controlling white perch. Cumulative frequency distributions facilitated interpretation by providing a graphical presentation of consumption rates by all individuals within each predator species. Largemouth bass Micropterus salmoides, walleye Sander vitreus and sauger S. canadensis were the most efficient white perch predators in both reservoirs; however, previous attempts to increase biomass of these predators have failed suggesting that successful biological control is unlikely using existing predator species in these Nebraska reservoirs.

The influence of aquatic predators on mosquito abundance in animal drinking troughs in New Zealand

The occurrence and abundance of mosquito populations may be associated with the abundance of predators. We examined the relationship between aquatic predators and populations of mosquitoes in animal water troughs in Waikanae, New Zealand. We also investigated the effects of water volume and environmental factors (temperature, rainfall, wind speed, humidity, and pressure) in order to further understand factors influencing mosquito and predator populations. Logistic regression indicated that the presence or absence of mosquitoes was primarily affected by three factors: predator abundance, week of observation, and water volume. Pearson's correlation indicated that the presence of predators had a positive correlation with water volume (r² = 0.176, p< 0.05). Otherwise, the presence of mosquito larvae in water troughs was negatively correlated with water volume (r² =-0.159, p=0.022) and wind speed (r² =0.142, p=0.041). We established a translocation experiment in which predators or mosquitoes were moved between troughs in order to examine the prey survival rate after exposure to Anisops wakefieldi predators. The survival rate of mosquitoes was not significantly different, between 0-0.1%, irrespective of the number of predators translocated (1-9) or the initial mosquito density (20-70 larvae). Our results suggested that A. wakefieldi predators may have the potential to be a promising biological control tool for the control of mosquito populations by altering mosquito population dynamics.

Intersectoral coordination, community empowerment and dengue prevention: six years of controlled interventions in Playa Municipality, Havana, Cuba

To document the process, outcome and effectiveness of a community-based intervention for dengue control. The primary intervention, focused on strengthening intersectoral coordination, was initiated by researchers in January 2000 in a pilot area in Playa municipality, Havana. In August 2002 health authorities extended the intervention to neighbouring areas, one of which was selected for evaluation. In August 2003 a complementary strategy, focused on community empowerment, was initiated in half of the pilot area. In our control area, routine dengue activities continued throughout the study period. Longitudinal process assessment was carried out using document analysis, interviews and group discussions. Random population surveys in 1999, 2002 and 2005 assessed levels of participation and behavioural changes. Entomological surveillance data from 1999 to 2005 were used to determine effectiveness. Mean scores for participation in the pilot area were 1.6, 3.4 and 4.4 at baseline, and 2 years after initiating intersectoral coordination and intersectoral coordination plus community empowerment interventions, respectively. While in the control area little behavioural change was observed over time, changes were considerable in the pilot and extension areas, with 80% of households involved in the community empowerment intervention showed adequate behavioural patterns. The pilot and extension areas attained comparable entomological effectiveness with significantly lower Breteau indices (BIs) than the control area. The pilot (sub-) area with the community empowerment intervention reached BIs below 0.1 that continued to be significantly lower than the one in the control area until the end of the study. The study showed a trend in the levels and quality of participation, behavioural change and effectiveness of Aedes control from the routine activities only over an intervention with intersectoral coordination to one that combined intersectoral coordination and community empowerment approach.

Biological control of horse cyathostomin (Nematoda: Cyathostominae) using the nematophagous fungus Duddingtonia flagrans in tropical southeastern Brazil

The viability of a fungal formulation using the nematode-trapping fungus Duddingtonia flagrans was assessed for the biological control of horse cyathostomin. Two groups (fungus-treated and control without fungus treatment), consisting of eight crossbred mares (3–18 years of age) were fed on Cynodon sp. pasture naturally infected with equine cyathostome larvae. Each animal of the treated group received oral doses of sodium alginate mycelial pellets (1 g/(10 kg live weight week)), during 6 months. Significant reduction ( p < 0.01) in the number of eggs per gram of feces and coprocultures was found for animals of the fungus-treated group compared with the control group. There was difference ( p < 0.01) of 78.5% reduction in herbage samples collected up to (0–20 cm) between the fungus-treated group and the control group, during the experimental period (May–October). Difference of 82.5% ( p < 0.01) was found between the fungus-treated group and the control group in the sampling distance (20–40 cm) from fecal pats. During the last 3 months of the experimental period (August, September and October), fungus-treated mares had significant weight gain ( p < 0.01) compared with the control group, an increment of 38 kg. The treatment with sodium alginate pellets containing the nematode-trapping fungus D. flagrans reduced cyathostomin in tropical southeastern Brazil and could be an effective tool for biological control of this parasitic nematode in horses.

Endophytes: An emerging tool for biological control

Scope and background of this compilation: In 2003, the Biological Control Committee of the American Phytopathological Society (APS) suggested that the time was right to develop a symposium on endophytes for the annual meeting of the society to be held in 2005. We were charged with developing a series of topics and speakers that would address the status of endophytes for biological control of plant diseases. That symposium was held in the 2005 meeting of APS, July 30–August 3 in Austin, Texas, where it generated very strong attendance. Preliminary abstracts of presentations were published for that meeting [Various, 2005. Endophytes, an emerging tool for biological control (six abstracts). Phytopathology 95(6), S138 (Suppl. 1)]. Authors from these presentations are largely represented in this compilation. In addition, we have added additional papers on fungal endophytes for plant disease and insect management.

Taxonomic status of the intracellular bacterium Wolbachia pipientis

Wolbachia pipientis is a maternally inherited, intracellular bacterium found in more than 20 % of all insects, as well as numerous other arthropods and filarial nematodes. It has been the subject of a growing number of studies in recent decades, because of the remarkable effects it has on its arthropod hosts, its potential as a tool for biological control of arthropods of agricultural and medical importance and its use as a target for treatment of filariasis. W. pipientis was originally discovered in cells of the mosquito Culex pipiens and is the only formally described member of the genus. Molecular sequence-based studies have revealed a number of phylogenetically diverse strains of W. pipientis. Owing to uncertainty about whether W. pipientis comprises more than one species, researchers in the field now commonly refer to W. pipientis simply as Wolbachia. In this note, we briefly review higher-level phylogenetic and recombination studies of W. pipientis and propose that all the intracellular symbionts known to cluster closely with the type strain of W. pipientis, including those in the currently recognized supergroups (A-H), are officially given this name.