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Biological Control Agents (biological + control_agent)
Kinds of Biological Control Agents 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] 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] 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] 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] 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] 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] 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] 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. [source] Genotype and temperature influence pea aphid resistance to a fungal entomopathogenPHYSIOLOGICAL ENTOMOLOGY, Issue 2 2003David A. Stacey Abstract. The influence of temperature on life history traits of four Acyrthosiphon pisum clones was investigated, together with their resistance to one genotype of the fungal entomopathogen Erynia neoaphidis. There was no difference among aphid clones in development rate, but they did differ in fecundity. Both development rate and fecundity were influenced by temperature, but all clones showed similar responses to the changes in temperature (i.e. the interaction term was nonsignificant). However, there were significant differences among clones in susceptibility to the pathogen, and this was influenced by temperature. Furthermore, the clones differed in how temperature influenced susceptibility, with susceptibility rankings changing with temperature. Two clones showed changes in susceptibility which mirrored changes in the in vitro vegetative growth rate of E. neoaphidis at different temperatures, whereas two other clones differed considerably from this expected response. Such interactions between genotype and temperature may help maintain heritable variation in aphid susceptibility to fungal pathogen attack and have implications for our understanding of disease dynamics in natural populations. This study also highlights the difficulties of drawing conclusions about the efficacy of a biological control agent when only a restricted range of pest genotypes or environmental conditions are considered. [source] Transfer of Nosema locustae (Microsporidia) to Antonospora locustae n. comb.THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2004Based on Molecular, Ultrastructural Data ABSTRACT. Nosema locustae is a microsporidian parasite of grasshopper pesthd that is used as a biological control agent, and is one of the emerging model systems for microsporidia. Due largely to its diplokaryotic nuclei, N. locustae has been classified in the genus Nosema, a large genus with members that infect a wide variety of insects. However, some molecular studies have cast doubt on the validity of certain Nosema species, and on the taxonomic position of N. locustae. To clarify the affinities of this important insect parasite we sequenced part of the rRNA operon of N. locustae and conducted a phylogenetic analysis using the complete small subunit rRNA gene. Nosema locustae is only distantly related to the nominotypic N. bombycis, and is instead closely related to Antonospora scoticae, a recently described parasite of bees. We examined the ultrastructure of mature N. locustae spores, and found the spore wall to differ from true Nosema species in having a multi-layered exospore resembling that of Antonospora (one of the distinguishing features of that genus). Based on both molecular and morphological evidence, therefore, we propose transferring N. locustae to the genus Antonospora, as Antonospora locustae n. comb. [source] Relationship between saprotrophic growth in soil of different biotypes of Pochonia chlamydosporia and the infection of nematode eggsANNALS OF APPLIED BIOLOGY, Issue 1 2009I.A. Siddiqui Abstract The ecology of Pochonia chlamydosporia in soil and its interaction with both plant and nematode hosts are important for the successful exploitation of the fungus as a biological control agent. Differences in saprotrophism and parasitism were assessed for biotypes of P. chlamydosporia, which had originated from the eggs of cyst or root-knot nematodes. Colonisation in soils of different textures (compost, sandy loam and loamy sand) measured by the numbers of colony-forming units, differed greatly. Most biotypes were more abundant in sterilised soil of the different textures compared with non-sterilised soils. The proportion of nematode eggs parasitised in a baiting technique demonstrated that biotypes had host preferences. Those biotypes that originated from root-knot nematodes (RKN-biotypes) infected significantly more Meloidogyne hapla eggs than Globodera pallida eggs, whereas biotypes from cyst nematodes (CN-biotypes) parasitised more G. pallida eggs than M. hapla eggs. Differences in virulence between biotypes in an in vitro assay in which the fungi were placed directly onto the egg masses of M. hapla and those differences observed in the baiting technique showed similar trends. There was a negative linear correlation between the growth of the eight biotypes in soil and the proportion of eggs they infected in compatible interactions (i.e. fungal biotype originated from the same nematode genus as the target eggs). Those biotypes that infected most nematode eggs colonised soil the least extensively, suggesting that virulence may have a fitness cost. However, the relationship between saprotrophic growth and virulence is complex. The relative abundance of the different biotypes in soil in Petri dish assays was similar to that under glasshouse conditions using potato but not tomato as the plant host. Chlamydospores of some biotypes applied to soil significantly reduced (>50%) the population densities of M. hapla on tomato and of G. pallida on potato plants. Some biotypes that were both effective and virulent are good candidates for biological control of specific nematode pests. Data presented here and elsewhere indicate that RKN-biotypes have different host preferences to CN-biotypes; the specific primers based on the vcp1 gene from P. chlamydosporia rapidly confirmed the host origin of seven of the eight biotypes. [source] Use of real-time quantitative PCR to investigate root and gall colonisation by co-inoculated isolates of the nematophagous fungus Pochonia chlamydosporiaANNALS OF APPLIED BIOLOGY, Issue 1 2009S.D. Atkins Abstract The fungus Pochonia chlamydosporia is a potential biological control agent for plant parasitic nematodes, but to date, there has been little investigation of interactions (competitive, antagonistic or synergistic) between different isolates that occur together on roots and nematode galls. Real-time quantitative PCR (qPCR) has greatly improved the study of many fungi in situ on plant and nematode hosts, but distinguishing closely related isolates remains difficult. In this study, primers to discriminate P. chlamydosporia var. chlamydosporia and P. chlamydosporia var. catenulata were used to measure the relative abundance of isolates of the two varieties when inoculated singly or together on tomato plants. Also, sequence-characterised amplified polymorphic regions were identified to distinguish two different isolates of P. chlamydosporia var. chlamydosporia. Individual 1-cm root segments and nematode galls were excised, DNA extracted and subjected to real-time qPCR with the discriminatory primers. The qPCR method proved sensitive and reproducible and demonstrated that roots and nematode galls were not uniformly colonised by the fungi. Results indicated that the P. chalmydosporia var. catenulata isolate was more abundant on roots and eggs than P. chlamydosporia var. chlamydosporia, but all the isolates infected a similar proportion of nematode eggs. There was an indication that the abundance of each fungal isolate was reduced in co-inoculation experiments compared with single inoculations, but the number of root segments and galls colonised was not statistically significantly different. [source] Colonisation pattern of nonpathogenic Fusarium oxysporum, a potential biological control agent, in roots and rhizomes of tissue cultured Musa plantletsANNALS OF APPLIED BIOLOGY, Issue 1 2006P. Paparu Abstract Under laboratory conditions, nonpathogenic, endophytic Fusarium oxysporum inflicts high mortality among banana weevils and nematodes. Following inoculation into banana (Musa spp.) tissue cultured plants, successful colonisation is necessary for efficient biological control of these pests. The pattern of root and rhizome colonisation by two nonpathogenic Ugandan F. oxysporum strains (V2w2 and III4w1) in cv. Nabusa (AAA-EA) was investigated using light microscopy. Percentage of colonisation in the rhizomes (93%) was higher than in the roots (56%), but hyphal density in the roots (0.30 mm,2) was higher than in the rhizomes (0.21 mm,2). The root bases were better colonised (76%) than root midsections (53%) or tips (39%). Both the strains colonised the roots and the rhizomes, with numerous hyphae infecting the hypodermis but fewer infecting the cortex. Colonisation of vascular tissues was not recorded. Despite the presence of hyphae in intercellular and intracellular spaces of the roots and the rhizomes, normal cell structure was observed. Our report provides the first in situ observation and quantification of endophyte colonisation in banana. The study demonstrated the ability of F. oxysporum strains V2w2 and III4w1 to penetrate intact host tissues and recolonise the host internally upon inoculation, an important step for their suitability as biological control agents. [source] Ecological role of control agent, and not just host-specificity, determine risks of biological controlAUSTRAL ECOLOGY, Issue 6 2010COLLEEN L. SEYMOUR Abstract Biological control agents used to manage alien vegetation are generally viewed as providing an ecosystem service, owing to reduced ecological and economic costs of invasion following their release. In particular, gall-formers are popular as biological control agents because they are host-specific and therefore considered low risk. However, galls can also be considered to be ecological engineers, because they provide nutritional resources for native invertebrates. We tested whether native invertebrates had formed associations with the gall-forming fungus Uromycladium tepperianum, introduced into South Africa to control the Australian invasive alien tree Acacia saligna, by collecting U. tepperianum galls and monitoring emergence. We found that a number of invertebrates had formed associations with the biological control agent, among which was the important citrus pest, Thaumatotibia leucotreta (false codling moth). We used pheromone-baited traps to ascertain if this supplementary source of T. leucotreta increased their abundance in orchards close to patches of gall host, but did not find this to be the case. We did find, however, that control measures used by farmers explained T. leucotreta abundances in traps, which may have obscured detection of any effects of a nearby host for the pest. Nevertheless, this study illustrates the first case of a host-specific classical biological control agent providing resources for an economically significant crop pest. We conclude that although biological control agents are strictly vetted to ensure host-specificity, introduced biological control agents that become abundant and can act as ecological engineers pose risks when native biota form associations with them, resulting in a number of possible cascading ecosystem effects. In addition, there could be economic consequences when these associated species include agricultural pests. We conclude that not just host specificity, but potential ecological effects of biological control agents, should be considered in their selection. [source] Two new species of Acizzia Crawford (Hemiptera: Psyllidae) from the Solanaceae with a potential new economic pest of eggplant, Solanum melongenaAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2010Deborah Kent Abstract Two new species of Acizzia Heslop-Harrison (Hemiptera: Psyllidae) from the plant family Solanaceae in eastern Australia are described. Acizzia solanicola sp. n. can damage eggplant, Solanum melongena (Solanaceae), in commercial crops and gardens in eastern Australia. It is a new, potentially serious commercial pest species, of which the nymphs induce malformation of leaves, produce copious amounts of viscous waste and cause leaf wilting, premature leaf senescence and crop loss. These psyllids have a unique and characteristic method of disposing of honeydew and this is illustrated for the first time. Acizzia alternata sp. n. is recorded from the weed, wild tobacco bush, Solanum mauritianum, but appears to cause little damage. These comprise the first record of a pest psyllid on eggplant and the first record of Acizzia from the Solanaceae. The parasitoid, Psyllaephagus sp. (Hymenoptera: Encyrtidae), is recorded parasitising nymphs of A. solanicola sp. n., and is here proposed as a potential biological control agent against it. [source] | |||||||||||||||||||||||||||||||||||||