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Control Agent (control + agent)
Kinds of Control Agent Selected AbstractsStrain E26 of Agrobacterium vitis, a Biological Control Agent of Grapevine Crown Gall, Does Not Contain virA and virG Pathogenic DeterminantsJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2009Qing Wei Abstract Risk assessment of biological control agents (BCAs) for the control of plant diseases in the field and/or laboratories has now become a necessary procedure before developing and producing novel BCAs. Agrobacterium vitis strain E26 is a promising potential biocontrol agent of grapevine crown gall disease. However, much less is understood about its safety or environmental risks. In this study, polymerase chain reaction (PCR) and Southern blot analyses were used to determine whether five essential virulence genes (virA, virG, iaaH, iaaM and ipt) were present in strain E26. Primers and probes were designed based on the conserved regions of each gene. The overall results obtained indicated that A. vitis strain E26 does not contain the virA and virG determinants, suggesting that this strain would be unlikely to elicit crown gall symptoms in either host or non-host plants. It seems that the iaaH, iaaM, or ipt gene were not present in strain E26 either. An applicable new approach combining PCR and Southern blot analyses to examine the pathogenicity of potential BCAs, particularly BCAs from the genus of Agrobacterium spp. was described. [source] Use of Bean Sprout Enterobacteriaceae Isolates as Biological Control Agents of Pseudomonas fluorescensJOURNAL OF FOOD SCIENCE, Issue 1 2004K. ENOMOTOArticle first published online: 28 JUN 200 ABSTRACT: Bean sprouts were cultivated under in vitro conditions as a model system to study the mechanism of bacteria-mediated spoilage in bean sprouts. Pseudomonas fluorescens, or Erwinia spp., were inoculated onto sprouts at several stages during cultivation. Five strains of Enterobacteriaceae isolated from the native microflora of sprouts prevented Pseudomonas -mediated spoilage by co-inoculating these cultures on seeds that were soaking in water. The population of P. fluorescens in co-inoculated liquid medium culture with a strain (B1) decreased slightly. The results indicated that the Enterobacteriaceae isolates tested played an important role in preventing Pseudomonas -mediated spoilage by growing competitively with P. fluorescens. [source] Phorid fly parasitoids of invasive fire ants indirectly improve the competitive ability of a native antECOLOGICAL ENTOMOLOGY, Issue 5 2004Natasha J. Mehdiabadi Abstract., 1.,The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), is an invasive species of south-eastern U.S.A. Since its introduction from South America approximately 70 years ago, this pest has devastated natural biodiversity. 2.,Due to such ecological costs, Pseudacteon phorid fly parasitoids (Diptera: Phoridae) from South America are being introduced into the U.S.A. as a potential biological control agent. Here, the indirect effects of these specialised parasitoids on an interspecific native ant competitor, Forelius mccooki (Hymenoptera: Formicidae), are evaluated. 3.,Over the course of a 50-day laboratory experiment, the results show that the native ant improved aspects of exploitative, but not interference, competition when S. invicta -attacking flies were present compared with when they were absent. 4.,Forelius mccooki colonies from the phorid treatment had approximately twice as many foragers at food baits relative to controls; however, there was no significant difference in interference aspects of competition or native ant colony growth between the two treatments. 5.,These results suggest that the S. invicta -specialised parasitoids help shift the competitive balance more in favour of F. mccooki than if these flies were not present; however, this competitive advantage does not translate into increased colony growth after 50 days. These laboratory findings are interpreted with regard to the more complex interactions in the field. [source] The impact of a parasitic nematode, Thripinema fuscum, on the feeding behavior and vector competence of Frankliniella fuscaENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2009Kelly R. Sims Abstract Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) is the predominant thrips species found inhabiting and reproducing in peanut, Arachis hypogaea L. (Fabaceae), and is one of at least seven thrips species reported to transmit Tomato spotted wilt virus (TSWV). The entomogenous nematode Thripinema fuscum Tipping & Nguyen (Tylenchida: Allantonematidae), a natural enemy of F. fusca, parasitizes larval and adult populations under field conditions. All known Thripinema species render the host female thrips sterile and have the potential to suppress pest populations to near extinction. As a result, secondary spread of TSWV in peanut is reduced. Reduction of the virus under field conditions may also be due to lower transmission rates caused by parasite-induced alterations in host feeding behavior. Therefore, the feeding rates of healthy and parasitized F. fusca male and female cohorts on leaf discs were recorded daily for 10 days and digital images were subjected to image analysis and viral transmission rates were compared daily using double antibody sandwich enzyme-linked immunosorbent assay. Thripinema fuscum reduced the feeding of female F. fusca by nearly 65%, and the ability of females to transmit TSWV by 50%. Potential mechanisms underlying the parasite-induced alterations in feeding behavior and transmission are discussed. Parasitism by T. fuscum significantly reduced male longevity, but female longevity was not affected. These results provide further evidence that T. fuscum aids in regulating viruliferous F. fusca pest populations and suggests its potential as a biological control agent for inoculative release in peanut. [source] Effect of temperature on development, overwintering and establishment potential of Franklinothrips vespiformis in the UKENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2007Eleni Larentzaki Abstract This study investigated the effect of temperature on the development and overwintering potential of the predatory thrips Franklinothrips vespiformis (Crawford) (Thysanoptera: Aeolothripidae), a biological control agent used against glasshouse pests in continental Europe and Israel. Developmental rates increased linearly with rearing temperatures. It was estimated that 304.9 degree days, above a lower threshold temperature of 11.9 °C, were required for F. vespiformis to complete development from egg to adult eclosion. The effect of low temperatures (,5, 0, and 5 °C) was examined on adult female and larval survival. Subsequent reproductive and developmental attributes of survivors were also investigated. Lethal time experiments indicated that larval stages are more cold tolerant than adult F. vespiformis females. Surviving larvae increased their developmental times to adults with decreasing temperature and increasing exposure periods and second instars were significantly more successful than first instars in reaching adulthood. Surviving adult females decreased their oviposition rate with decreasing temperature and increasing exposure periods, and exposures to low temperatures affected the number of viable eggs produced. The results are discussed in the context of overwintering and establishment potential of F. vespiformis in the UK in the event of introducing the predatory thrips as a biological control agent against glasshouse pests. [source] Insecticidal effects of selected biological control agents on the larvae of Plutella xylostella (Lepidoptera: Plutellidae)ENTOMOLOGICAL RESEARCH, Issue 2 2007Ömer ERTÜRK Abstract To identify a more effective and safe biological control agent against a common cabbage pest, Plutella xylostella (L.) (Lepidoptera: Plutellidae), the insecticidal effects of selected biological agents were evaluated. The highest insecticidal effects determined were 100, 73.5, 45.5, 47 and 55.3% using toxin HD-1 (isolated from the Harry Dumagae strain of Bacillus thuringiensis), toxin BTS-1 (isolated from the tenebrionis strain of B. thuringiensis), B. thuringiensis Berliner, B. thuringiensis israelensis and B. thuringiensis kurstaki, respectively. [source] Susceptibility of the leaf-eating beetle, Galerucella calmariensis, a biological control agent for purple loosestrife (Lythrum salcaria), to three mosquito control larvicidesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2004T. Peter Lowe Abstract We evaluated the susceptibility of Galerucella calmariensis, a species used to control purple loosestrife (Lythrum salicaria), to three mosquito control larvicides. Larvae and adults were fed loosestrife cuttings dipped in Abate® (,375 g · L,1), Altosid® (,250 g · L,1), and Bacillus thuringiensis var israeliensis (Bti) (<110 g · L,1). Eggs on cuttings were dipped in the same concentrations. Pupae were immersed in Abate and Altosid solutions (,474.4 ,g · L,1 and ,1,169.2 ,g · L,1, respectively). Hatching success of eggs dipped in Abate (,3.75 g · L,1) was reduced significantly and survival was significantly lower among larvae and adults eating cuttings dipped in Abate (,0.17 g · L,1 and ,2.27 g · L,1, respectively). Hatching success of eggs dipped in Altosid (,2.52 g · L,1) was reduced significantly. With exposure to Altosid, larval survival to pupation and adult emergence was reduced significantly at concentrations of ,2.92 g · L,1 and ,0.63 g · L,1, respectively. Altosid (,0.23 g · L,1) also delayed the onset of pupation and adult emergence among larvae that survived to pupate. Larvae that survived with exposure to Altosid (,1.72 g · L,1) grew to 70% larger than those exposed to lower concentrations. Pupal survival was unaffected with exposure to Abate and Altosid and adult survival was unaffected with exposure to Altosid. Bacillus thuringiensis var israeliensis did not adversely affect any life stage of G. calmariensis. The mean Abate concentration on cuttings exposed to operational spraying was in the range that reduced egg hatchability and adult survival but was higher than concentrations that caused complete mortality of larvae. The mean Altosid concentration on cuttings exposed to operational spraying was in the range that reduced hatching success in eggs and delayed pupation and adult emergence of larvae. [source] Detection of nematode antagonistic bacteria by fluorogenic molecular probes,EPPO BULLETIN, Issue 3-4 2000A. Ciancio Last-generation DNA probes include molecules yielding a fluorogenic emission through an intramolecular change occurring after hybridization to a complementary sequence. They display a high sequence specificity and may detect even single-base mutations in polymerase chain reaction (PCR) amplification products. We applied Scorpion primers for the detection of an unculturable nematode-parasitic bacterium, Pasteuria sp., with potential as a biological control agent. A 16S rDNA oligonucleotide sequence unique to Pasteuria spp. was used to detect the parasite in juveniles of Heterodera goettingiana or in soil. The parasitized nematodes came from a population with a Pasteuria prevalence of 40,80% and were individually checked for parasitism. Probes with 6-carboxy-fluorescein (FAM) at the 5'terminus, used for PCR with nematodes or soil, successfully detected the parasite from both samples. The amplification of the expected 139bp fragment was shown both by fluorescence observed under UV excitation in the eppendorfs and by gel electrophoresis of the corresponding amplicons. The potential of this detection method for the study of unculturable bacteria is discussed. [source] Mycoparasitism of arbuscular mycorrhizal fungi: a pathway for the entry of saprotrophic fungi into rootsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2010Nathalie De Jaeger Abstract Within the rhizosphere, arbuscular mycorrhizal (AM) fungi interact with a cohort of microorganisms, among which is the biological control agent, Trichoderma spp. This fungus parasitizes a wide range of phytopathogenic fungi, a phenomenon also reported in the extraradical mycelium (ERM) of AM fungi. Here, we question whether the mycoparasitism of the ERM could be extended to the intraradical mycelium (IRM), thus representing a pathway for the entry of Trichoderma harzianum within the root. Microcosm experiments allowing interactions between Glomus sp. MUCL 41833 placed in a clade that contains the recently described species Glomus irregulare and T. harzianum were set up under in vitro autotrophic culture conditions using potato as a host. A microscope camera-imaging system, coupled with succinate dehydrogenase staining, was used to assess the mycoparasitism in the ERM and IRM. Trichoderma harzianum colonized the ERM of the AM fungus and spread into the IRM, before exiting into the root cells. Intrahyphal growth of T. harzianum caused protoplasm degradation, decreasing the ERM and IRM viability. ERM of the AM fungus represented a pathway for the entry of T. harzianum into the roots of potato. It further sets off the debate on the susceptibility of the AM fungi of being infected by microorganisms from the rhizosphere. [source] Osmotic shock tolerance and membrane fluidity of cold-adapted Cryptococcus flavescens OH 182.9, previously reported as C. nodaensis, a biocontrol agent of Fusarium head blightFEMS YEAST RESEARCH, Issue 3 2007Christopher A. Dunlap Abstract Cryptococcus flavescens (previously reported as C. nodaensis), a biological control agent of Fusarium head blight, has been previously shown to have improved desiccation tolerance after cold adaptation. The goal of the current study was to determine the effect of cold adaptation on the physicochemical properties of C. flavescens that may be responsible for its improved desiccation tolerance. The results show that cold adaptation improves liquid hyperosmotic shock tolerance and alters the temperature dependence of osmotic shock tolerance. Fluorescence anisotropy was used to characterize differences in the membrane fluidity of C. flavescens with and without cold adaptation. Force curves from atomic force microscopy showed a significant increase in the cell wall spring constant after cold adaptation. Cold adaptation of C. flavescens during culturing was shown to produce smaller cells and produced a trend towards higher CFU yields. These results suggest that cold adaptation significantly alters the membrane properties of C. flavescens and may be an effective method of improving the desiccation tolerance of microorganisms. In addition, we provide information on the correct naming of the isolate as C. flavescens. [source] A conceptual framework for agent-based agile manufacturing cellsINFORMATION SYSTEMS JOURNAL, Issue 2 2004Jianming Yu Abstract., Agile manufacturing techniques are perceived as the manufacturing systems of the future. Agile manufacturing cells are dynamic and reconfigurable and the modelling of the manufacturing cells and its interaction mechanism is critical to its successful use. This paper deals with the architecture and cooperation mechanism of web-based agile manufacturing cells. Based on an analysis of structure and organization requirements of agile manufacturing cells and a comparison of three basic architectures of manufacturing systems, the quasi-heterarchical architecture is used for the agile manufacturing cell. Functional layers are defined in this architecture to make the cell's control system reconfigurable and reusable. Agent technology is adopted for implementation of each layer's functions to establish an agent-based model of agile manufacturing cells. Four types of agents including cooperation agent, job management agent, resource broker agent, and resource control agent are defined, and their functions discussed. Finally, a real time interaction mechanism of the agents is presented by considering the activities during the agents' cooperation in an agile manufacturing cell. [source] Eggload dynamics and oviposition rate in a wild population of a parasitic waspJOURNAL OF ANIMAL ECOLOGY, Issue 2 2000Jérôme Casas Summary 1.,This paper develops and tests in the field a model that predicts the oviposition rate and the rate of egg maturation of a synovigenic parasitic wasp during a foraging period. The parasitoid is Aphytis melinus, the highly successful biological control agent of California redscale (Aondiniella aurantii), a pest of citrus worldwide. 2.,Females were sampled in the interior canopy of grapefruit trees either just before and at the end of the foraging period over 2 days and were dissected to determine the starting and ending eggload distributions. A group of females was caught before the onset of activity and kept in vials in the field in trees with honey but without access to hosts during the foraging period. Their eggload at the end of the day was used to estimate the egg maturation rate during the foraging period. 3.,Two stochastic models are used to predict the eggload distribution at the end of the day. Both use the observed starting eggload distribution, the observed length of the foraging period and the estimated rate of egg maturation. The model providing the better fit uses an oviposition rate which is an increasing function of the eggload. 4.,The eggload does not attain a steady state distribution during a foraging period. One-third to one-half of the population is predicted to experience egg-limitation at some time during the foraging period. Five percent of the population will experience egg-limitation a second time within a single day. 5.,The common occurrence of egg-limitation over a single day and the relatively high rate of change of states between egg- and time-limitation imply that the rate of nutrient acquisition and use are likely to be subject to strong evolutionary pressures. [source] Management implications of the Macquarie Island trophic cascade revisited: a reply to Dowding et al. (2009)JOURNAL OF APPLIED ECOLOGY, Issue 5 2009Dana M. Bergstrom Summary 1. The management of non-indigenous species is not without its complications. In Bergstrom et al.'s (2009) study, we demonstrated that feral cats Felis catus on sub-Antarctic Macquarie Island were exerting top-down control on the feral rabbit Oryctolagus cuniculus population, and that the eradication of the cats led to a substantial increase in rabbit numbers and an associated trophic cascade. 2. Dowding et al. (2009) claim our modelling was flawed for various reasons, but primarily that a reduction in the application of the rabbit control agent, Myxoma virus, coinciding with cat removal, was a major driver of rabbit population release. 3. We explore this proposition (as well as others) by examining rates of Myxoma viral release between 1991 and 2006 (with an attenuation factor for the years, 2003,2006) in association with presence/absence of cats against two estimates of rabbit population size. Myxoma viral release was a significant factor in the lower estimates of rabbit population, but the effect was small, and was not significant for higher rabbit population estimates. By contrast, the presence or absence of cats remained highly significant for both estimates. 4.Synthesis and applications. We re-affirm our position that top-down control of rabbit numbers by cats, prior to their eradication, was occurring on Macquarie Island. Nonetheless, we agree with Dowding et al. (2009) that systems with multiple invasive species represent complex situations that require careful scrutiny. Such scrutiny should occur in advance of, during, and following management interventions. [source] East meets west: adaptive evolution of an insect introduced for biological controlJOURNAL OF APPLIED ECOLOGY, Issue 3 2008C. B Phillips Summary 1A possible explanation for low success rates when introducing natural enemies to new regions for biological control of insect pests is that they fail to adapt to their new conditions. Therefore it has been widely recommended that biological control practitioners increase the probability of local adaptation by maximizing the genetic variation released. An alternative recommendation is to use climate matching to identify native populations that may already possess traits suited to the new region. However, support for these recommendations is weak through lack of empirical evidence that local adaptation is important to biological control. 2This study examined how genetic drift and selection influenced the population frequencies of two asexually reproducing, genetically differentiated parasitoid biotypes that were introduced to New Zealand from South America for biological control. Other than by mutation, the biotypes were genetically fixed due to the absence of recombination both within and between biotypes. This meant that adaptive evolution could occur only if selection acted on any traits that varied between the biotypes introduced from South America. 3The two parasitoid biotypes were released simultaneously at 14 sites and their frequencies were monitored for up to 10 years. Changes in biotype frequency were consistent with strong directional selection favouring one of the South American biotypes, thus generating established parasitoid populations that were better adapted to New Zealand conditions than those that had originally been released. This local adaptation of the control agent contributed to greater mortality of the pest. 4Synthesis and applications. This study provides the first clear demonstration of the importance of releasing natural enemy genetic variation in new regions to foster adaptive evolution and improve success rates in classical biological control. However, the benefit to biological control of maximizing the genetic variation released needs to be balanced against possible risks to non-target species. The results do not support the concept of choosing sampling sites for putative biological control agents based solely on climatic similarities between the source location and the intended region of introduction. [source] Biology of Mastrus ridibundus (Gravenhorst), a potential biological control agent for area-wide management of Cydia pomonella (Linneaus) (Lepidoptera: Tortricidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2010L. Devotto Abstract The codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is a serious pest of pome fruit crops. A natural enemy of codling moth, the larval ectoparasitoid Mastrus ridibundus (Gravenhorst) (Hymenoptera: Ichneumonidae) has been imported into South America from the USA but little is known about the biology and ecology of the wasp, knowledge that is needed to design an efficient strategy of release and establishment. Experiments were carried out to assess important traits of the biology of the parasitoid in relation to its possible use as a biocontrol agent for codling moth. When M. ridibundus females were offered larvae ranging in weight from 37 to 78 mg, they oviposited more eggs on heavier hosts. In another study, the adult wasps were offered honey, diluted honey (10%) or pollen in paired choice tests and both males and females preferred honey over the other two foods. Females preferred 10% honey over pollen, while the males showed the opposite preference. Honey-fed females lived longer than starved females. Adults died rapidly at 35°C, while they lived 20 days at 25°C and 12,17 days at 15°C. Female wasps had on average 25 ± 14 and 18 ± 11 progeny at 15 and 25°C, respectively, but they did not had progeny at 35°C. The development time (egg to adult emergence) was on average 44 ± 7 and 24 ± 2 days at 15 and 25°C respectively. Immature insects did not reach the adult stage at 35°C. [source] Biology and host specificity of Aulacobaris fallax (Coleoptera: Curculionidae), a potential biological control agent for dyer's woad, Isatis tinctoria (Brassicaceae) in North AmericaJOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2009E. Gerber Abstract Dyer's woad, Isatis tinctoria, a plant of Eurasian origin is a problematic weed in western North America against which a classical biological weed control programme was initiated in 2004. Three European insect species were selected as candidate agents to control this invasive species, including the root-mining weevil Aulacobaris fallax. To determine its suitability as an agent, the biology and host specificity of A. fallax were studied in outdoor plots and in the field between 2004 and 2006 in its native European range. Aulacobaris fallax is a univoltine species that lays its eggs from March to August into leaf stalks and roots of dyer's woad. Larvae mine and pupate in the roots and adults emerge from August to October. Up to 62% of the dyer's woad plants at the field sites investigated were attacked by this weevil. In no-choice host-specificity tests, A. fallax attacked 16 out of 39 species and varieties within the Family Brassicaceae. Twelve of these are native to North America. In subsequent multiple-choice tests, seven species, all native to North America, suffered a similar level of attack as dyer's woad, while none of the European species were attacked. Our results demonstrate the importance of including test plant species that have not co-evolved with the respective candidate agent. In sum, we conclude that the risk of non-target effects is too high for A. fallax to be considered as a biological control agent for dyer's woad in the United States. [source] The fate of an intentional introduction of Formica lugubris to North America from EuropeJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2008A. J. Storer Abstract Red wood ants (Formica s.str.) are not prevalent in the forests of North America, but commonly occur in conifer and mixed conifer forests in northern Europe and Asia. In 1971, a European red wood ant species, Formica lugubris, was intentionally established in a 35-year-old predominantly mixed conifer plantation approximately 30 km north of QC, Canada. The purpose of its introduction was to evaluate the potential of this species as a biological control agent against conifer-defoliating Lepidoptera species. This red wood ant introduction was monitored periodically for about 5 years after establishment, but its long-term fate has not been reported. We visited this field site in 2005 and found that this species was well established, and we could locate some of the nests that resulted from the original release. We mapped and measured over 100 nests around the site of original release, which ranged from 5 cm in height to over 1 m. We estimated the population of introduced ants to have grown to over 8 million in the last 34 years. Significant clustering of nests suggests that these nests may be one supercolony. F. lugubris has become a dominant understory arthropod in this mixed forest, and is likely to have ecological impacts, including effects at the community and ecosystem level. [source] Baseline susceptibility of western corn rootworm (Coleoptera: Chrysomelidae) to clothianidinJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2007L. C. Magalhaes Abstract:, Western corn rootworm, Diabrotica virgifera virgifera LeConte, neonate susceptibility to clothianidin, a contact and systemic neonicotinoid insecticide, was determined from both laboratory and field-collected populations. Neonates were exposed to filter paper treated with increasing clothianidin concentrations and mortality was evaluated after 24 h. Additionally, two populations were exposed to an artificial diet which was surface treated with clothianidin. Although larvae were five- to six-fold more sensitive to treated diet, results with treated filter paper were more reliable in terms of control mortality and required much less manipulation of rootworm larvae. Therefore, initial baseline comparisons were conducted using the filter paper assays. The variation among populations exposed to treated filter paper was generally low, 4.4-fold among laboratory populations tested; however, there was a 14.5-fold difference in susceptibility among all populations tested. In general, clothianidin was very toxic to rootworm neonates, with LC50 values ranging from 1.5 to 21.9 ng/cm2. These results indicate the practicability and sensitivity of the paper filter disc assay to establish baseline susceptibility levels, which is an essential first step in resistance management. A baseline response provides a reference for tracking shifts in susceptibility following commercialization of a control agent so that early changes in susceptibility can be detected. [source] Control of Plutella xylostella using polymer-formulated Steinernema carpocapsae and Bacillus thuringiensis in cabbage fieldsJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2005S. Schroer Abstract:, Field trials evaluating the potential of the entomopathogenic nematode Steinernema carpocapsae and the feasibility to combine nematodes with Bacillus thuringiensis for sustainable control of the diamondback moth (DBM) Plutella xylostella were conducted in cabbage cultivated in the province Probolinggo, east Java and Indonesia. A single use of 0.5 million S. carpocapsae m,2 applied with a surfactant-polymer-formulation containing 0.3% xanthan and 0.3% Rimulgan® achieved a significant reduction of the insects per plant with >50% control after 7 days. Even 14 days after the application about 45% control was recorded and dead larvae containing nematodes were found. No significant effects were recorded when the formulation was compared with nematodes applied in water or with a surfactant alone. This was attributed to high humidity in the experimental area at the end of the rainy season and a microclimate in the cabbage heads favouring nematode survival. Weekly applications of B. thuringiensis (Turex®) or alternating applications of Turex® and the nematodes achieved >80% control. The application of both biological agents together every second week reached insignificant lower efficacy (70%). Nematodes can be used to substitute ineffective chemical insecticides and alterations with B. thuringiensis can prevent the further development of resistance against the bacterial control agent. [source] Riot control agents: pharmacology, toxicology, biochemistry and chemistry,JOURNAL OF APPLIED TOXICOLOGY, Issue 5 2001Eugene J. Olajos Abstract The desired effect of all riot control agents is the temporary disablement of individuals by way of intense irritation of the mucous membranes and skin. Generally, riot control agents can produce acute site-specific toxicity where sensory irritation occurs. Early riot control agents, namely, chloroacetophenone (CN) and chlorodihydrophenarsazine (DM), have been replaced with ,safer' agents such as o -chlorobenzylidene malononitrile (CS) and oleoresin of capsicum (OC). Riot control agents are safe when used as intended: however, the widespread use of riot control agents raises questions and concerns regarding their health effects and safety. A large margin exists between dosages that produce harassment and dosages likely to cause adverse health effects for modern riot control agents such as CS and dibenz[b,f]1 : 4-oxazepine (CR). Yet, despite the low toxicity of modern riot control agents, these compounds are not entirely without risk. The risk of toxicity increases with higher exposure levels and prolonged exposure durations. Ocular, pulmonary and dermal injury may occur on exposure to high levels of these substances, and exposure to riot control agents in enclosed spaces may produce significant toxic effects. Reported deaths are few involving riot control agents, and then only under conditions of prolonged exposure and high concentrations. Recently, concern has focused on the deaths resulting from law enforcement use of OC, a riot control agent generally regarded as safe because it is a natural product. As with other xenobiotics, not enough is known concerning the long-term/chronic effects of riot control agents. Clearly, there is considerable need for additional research to define and delineate the biological and toxicological actions of riot control agents and to illuminate the full health consequences of these compounds as riot control agents. Copyright © 2001 John Wiley & Sons, Ltd. [source] How should the risk associated with the introduction of biological control agents be estimated?AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2010Earl D. McCoy 1Florida has an exceptional burden of invasive species. The history of the classical biological control of invasive arthropod pest species in the region largely is one of inadequate pre-release testing for nontarget effects. 2A recent analysis indicated that a substantial risk of nontarget effects may exist in Florida, although the risk appears to be confined to a relatively small group of species within approximately ten families and documented cases of nontarget effects are rare, despite previous risky practices. 3Great progress has been made recently in creating an organized framework for dealing with the uncertainty accompanying biological control importations in Florida and elsewhere. We suggest some ways in which balancing the risks and associated costs of releasing a biological control agent against the risks and associated costs of not releasing the agent may be improved. 4Ultimately, experts will need to set some level of acceptable risk, and the ,precautionary principle' has been advanced to guide this process. As it stands, however, the precautionary principle applied to biological control falls short as a guide because it does not provide a prescription for action. 5Florida case histories clearly illustrate both the complexity and urgency related to developing a prescription for action. [source] A historical review of research on the weaver ant Oecophylla in biological controlAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2008Paul Van Mele Abstract 1,Although the weaver ant Oecophylla is the first written record of biological control, dating from 304 ad, there have been fewer than 70 scientific publications on this predator as a biological control agent in Asia, from the early 1970s onwards, and fewer than 25 in Africa. 2,Apart from crop-specific ecological and perceptual factors, a historical review shows that political and market forces have also determined the extent to which Oecophylla was incorporated into research and development programmes. 3,In Africa, research on weaver ants in biological control concentrated on export crops, such as coconut and cocoa, whereas, in Asia and Australia, research focused on fruit and nut crops, primarily destined for domestic markets. 4,Increased evidence of pesticide inefficiency under tropical smallholder conditions, changing paradigm shifts in participatory research and a growing scientific interest in local knowledge in the early 1990s opened up new avenues for research on conservation biological control. 5,Lobbying and advocacy have been needed to ensure that Oecophylla was recognized as an effective biological control agent. 6,With an increased market demand for organic produce, holistic approaches such as conservation biological control, particularly the use of Oecophylla, are increasing in importance. 7,Multi-stakeholder strategies for collaborative learning are proposed for a better control of major fruit, nut and timber tree pests in Africa, Asia and Australia. [source] 97 Sensitivity of cyanobacteria to a potential biological control agent, bacterium SG-3JOURNAL OF PHYCOLOGY, Issue 2003K. Wilkinson Cyanobacteria cause many problems in freshwater ecosystems. For example, the production of off-flavor compounds by cyanobacteria causes serious problems in catfish aquaculture. Control of cyanobacteria is generally limited to treatment with copper compounds, which are non-selective and sometimes ineffective at controlling certain species of cyanobacteria. Biological control could provide selective management by removing unwanted species while leaving desirable algae species. A bacterium (SG-3) (NRRL B-30043) lyses a number of planktonic species of cyanobacteria including bloom-forming species of Anabaena and Oscillatoria. We tested SG-3 for activity against 10 isolates, representing seven species, of mat-forming cyanobacteria within the genera Oscillatoria, Lyngbya, and Phormidium. Plugs (0.5 cm diameter) were cut from mats of the cyanobacterium, inoculated with liquid cultures of SG-3, and incubated as static cultures. The reduction in dry weights ranged from ,0.5% to 90% compared to the untreated controls and appeared to be species specific. For example, dry weight reductions of Oscillatoria deflexoides and O. amoena ranged from 80 to 90% whereas the reduction of O. limosa tended to be lower at 36 to 72%. Although results varied among and within species, they indicate that this bacterium could have potential for use as a biological control for mat-forming cyanobacteria. Light microscopic observations indicate the bacteria do not penetrate the cyanobacteria cells. Currently, we are studying the possible causes of the observed cell lysis. [source] Biological Control of Fusarium oxysporum f.sp. lycopersici on Tomato by Brevibacillus brevisJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2010Sunita Chandel Abstract The ability of Brevibacillus brevis to influence development of disease on tomato caused by Fusarium oxysporum f.sp. lycopersici was investigated using plants raised in Petri dish microcosms and in pots in the glasshouse. Development of symptoms on both microcosm- and glasshouse-raised tomato plants was markedly reduced in co-inoculations of F. oxysporum f.sp. lycopersici with B. brevis, compared with inoculations with the pathogen alone. Moreover, co-inoculations resulted in significant growth boosting effects on the plants, with increases in plant height in microcosms and in total root lengths in glasshouse-raised plants. In microcosm-raised plants, the carrier used to inoculate seed with B. brevis, either carboxymethyl cellulose (CMC) or vermiculite, had no effect on the persistence of the biological control agent on roots in the absence of inoculation with the pathogen. By contrast, numbers of B. brevis recovered from the rhizosphere and rhizoplane of inoculated plants in microcosms were four orders of magnitude lower than in plants treated with B. brevis alone. Moreover, higher numbers of B. brevis CFU were re-isolated from the rhizosphere of plants arising from CMC-coated seed, than vermiculite-coated seed. The carrier had no effect on disease control. Inhibition of conidial germination and germ-tube extension of F. oxysporum f.sp. lycopersici by cell-free filtrates of B. brevis cultures varied significantly depending on the culture medium used for suspension. These results indicate that B. brevis is a potential biological control agent for reducing the impact of F. oxysporum f.sp. lycopersici on tomato. [source] Synthesis and kinetic analysis of DPE controlled radical polymerization of MMAJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009Ying-Da Luo Abstract The 1,1-diphenylethene (DPE) controlled radical polymerization of methyl methacrylate was performed at 80 °C by using AIBN as an initiator and DPE as a control agent. It was found that the molecular weight of polymer remained constant with monomer conversion throughout the polymerization regardless of the amounts of DPE and initiator in formulation. To understand the result of constant molecular weight of living polymers in DPE controlled radical polymerization, a living kinetic model was established in this research to evaluate all the rate constants involved in the DPE mechanism. The rate constant k2, corresponding to the reactivation reaction of the DPE capped dormant chains, was found to be very small at 80 °C (1 × 10,5 s,1), that accounted for the result of constant molecular weight of polymers throughout the polymerization, analogous to a traditional free radical polymerization system that polymer chains were terminated by chain transfer. The polydispersity index (PDI) of living polymers was well controlled <1.5. The low PDI of obtained living polymers was due to the fact that the rate of growing chains capped by DPE was comparable with the rate of propagation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source] Competitive exclusion as a mode of action of a novel Bacillus cereus aquaculture biological agentLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2010R. Lalloo Abstract Aims:, To determine the contribution of potential modes of action of a Bacillus cereus aquaculture biological control agent in inhibition of the fish pathogen, Aeromonas hydrophila. Methods and Results:, When B. cereus was tested in plate well inhibition studies, no production of antimicrobial compounds was detected. Bacillus cereus had a high growth rate (0·96 h,1), whereas Aer. hydrophila concentration decreased by c. 70% in co-culture experiments. In nutrient limitation studies, B. cereus had a significantly higher growth rate when cultured under glucose (P < 0·05) and iron (P < 0·01) limitation in comparison with Aer. hydrophila. Bacillus cereus glucose (0·30 g l,1 h,1) and iron (0·60 mg l,1 h,1) uptake rates were also significantly higher (P < 0·01) than the Aer. hydrophila glucose (0·14 g l,1 h,1) and iron (0·43 mg l,1 h,1) uptake rates. Iron uptake was facilitated by siderophore production shown in time profile studies where relative siderophore production was c. 60% through the late exponential and sporulation phases. Conclusions:, Competitive exclusion by higher growth rate, competition for organic carbon and iron, facilitated by siderophore production, could be identified as mechanisms of pathogen growth inhibition by B. cereus. Significance and Impact of the Study:, This study is the first elucidation of the mechanism of action of our novel B. cereus biological agent in growth attenuation of pathogenic Aer. hydrophila. This study enhances the application knowledge and attractiveness for adoption of B. cereus NRRL 100132 for exploitation in aquaculture. [source] Selective medium based on tyrosine metabolism for the isolation and enumeration of Brevibacillus brevis (Bacillus brevis)LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2000S.G. Edwards Aims: To develop a selective medium for the enumeration of Brevibacillus brevis Nagano spores from soil and plant material. Methods and Results: Tyrosine agar was developed as a selective medium and compared with nutrient agar for the enumeration of B. brevis Nagano spores from sterile and non-sterile plant and soil extracts. Brevibacillus brevis Nagano colonies could be easily identified only on tyrosine agar due to their clear halo and distinct colony morphology. Identification was confirmed by thin layer chromatography of the antibiotic, gramicidin S, produced by this strain. Conclusions: Tyrosine agar was shown to be a suitable selective medium for the enumeration of B. brevis Nagano. Significance and impact of the study: The medium developed, tyrosine agar, can be used to monitor the population of the biological control agent, B. brevis Nagano, and will allow detailed studies within the crop environment. [source] Pantoea ananatis: an unconventional plant pathogenMOLECULAR PLANT PATHOLOGY, Issue 3 2009TERESA A. COUTINHO SUMMARY Pantoea ananatis causes disease symptoms in a wide range of economically important agricultural crops and forest tree species worldwide. It is regarded as an emerging pathogen based on the increasing number of reports of diseases occurring on previously unrecorded hosts in different parts of the world. Its unconventional nature lies in the fact that, unlike the majority of plant pathogenic microbes, P. ananatis is capable of infecting humans and occurs in diverse ecological niches, such as part of a bacterial community contaminating aviation jet fuel tanks and contributing to growth promotion in potato and pepper. Taxonomy: Bacteria; Gammaproteobacteria; family Enterobacteriaceae; genus Pantoea. Microbiological properties: Gram-negative; facultatively anaerobic; most strains are motile and produce a yellow pigment in culture; indole positive. Biology:Pantoea ananatis is a common epiphyte; it also occurs endophytically in hosts where it has been reported to cause disease symptoms and in hosts where no such symptoms have been described. Some strains are ice-nucleating, a feature which has been used as a biological control mechanism against some insect pests of agricultural crops and by the food industry. Disease symptoms:Pantoea ananatis infects both monocotyledonous and dicotyledonous plants. The symptoms are diverse depending on the host infected, and include leaf blotches and spots, die-back, and stalk, fruit and bulb rot. Biological control agent:Pantoea ananatis has both antifungal and antibacterial properties. These characteristics have the potential of being exploited by biological control specialists. [source] Biological control of terrestrial molluscs using Phasmarhabditis hermaphrodita,progress and prospectsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 12 2007Robbie Rae Abstract Phasmarhabditis hermaphrodita Schneider (Nematoda: Rhabditidae) is a nematode that parasitises a wide range of slug and snail species. It has been formulated into a biological control agent (Nemaslug®) and was commercialised in 1994. It is now available in fourteen European countries. A review is given of all research on P. hermaphrodita, including basic biology, mass cultivation, formulation, host range, application strategies, field efficacy and effects on non-target organisms. The many critical gaps in present knowledge are highlighted, and future research is proposed that will lead to greater understanding of this unusual parasite and may enable its more widespread use in the management of mollusc pests. Copyright © 2007 Society of Chemical Industry [source] U.K. winter egg survival in the field and laboratory diapause of Typhlodromips montdorensisPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2005Ian S. Hatherly Abstract.,Typhlodromips montdorensis has potential for release as a glasshouse biological control agent in the U.K. against thrips and spider mites. This study investigates the field survival in the U.K. of T. montdorensis when released as eggs, and the diapause response when reared in a regime related to its location of origin. All acclimated and nonacclimated eggs of T. montdorensis die in the field within 7 days of exposure. It is not possible to induce diapause in T. montdorensis reared at 21 °C under a LD 11 : 13 h photoperiod. The results presented here support the view that T. montdorensis is unlikely to survive a U.K. winter outside of the glasshouse environment, and contribute to the understanding of the biology of this little known species. 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