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PubMed2006

Assessment of the environmental fate of the biological control agent of fire blight, Pseudomonas fluorescens EPS62e, on apple by culture and real-time PCR methods.

The colonization of apple blossoms and leaves by Pseudomonas fluorescens EPS62e was monitored in greenhouse and field trials using cultivable cell counting and real-time PCR. The real-time PCR provided a specific quantitative method for the detection of strain EPS62e. The detection level was around 10(2) cells g (fresh weight)(-1) and the standard curve was linear within a 5-log range. EPS62e actively colonized flowers reaching values from 10(7) to 10(8) cells per blossom. In apple flowers, no significant differences were observed between population levels obtained by real-time PCR and plating, suggesting that viable but nonculturable (VBNC) cells and residual nondegraded DNA were not present. In contrast, on apple leaves, where cultivable populations of EPS62e decreased with time, significant differences were observed between real-time PCR and plating. These differences indicate the presence of VBNC cells or nondegraded DNA after cell death. Therefore, the EPS62e population was under optimal conditions during the colonization of flowers but it was stressed and poorly survived on leaves. It was concluded that for monitoring this biological control agent, the combined use of cultivable cell count and real-time PCR is necessary.

Colony Count, Microbial↗
PubMedDate not supplied

Nematophagous fungi as a biological control agent for nematode parasites of small ruminants in Malaysia: a special emphasis on Duddingtonia flagrans.

Approximately 2,800 fresh dung samples from animals, mainly ruminant livestock, were screened for the presence of nematophagous fungi in Malaysia. Arthrobotrys spp. was noted on numerous occasions, but only one isolate of Duddingtonia flagrans was made. For the purposes of producing sufficient quantities of this fungus for feeding trials in sheep, various, commonly available, cheap plant materials were tested as possible growth substrates. This showed that cereal grains (wheat, millet and rice) were the best media for fungal growth. Pen feeding trials were carried out using sheep, both naturally and experimentally infected with nematode parasites (predominantely Haemonchus contortus), to test the efficiency of D. flagrans when administered either in a grain supplement, or incorporated into a feed block. These showed that the fungus survived gut passage in sheep and that dose rates of approximately 1 x 10(6) D. flagrans spores / animal / day, reduced the percentage of infective larvae developing in faecal cultures by more than 90%. These results indicate that using D. flagrans as a biological control agent of nematode parasites, is a promising alternative to nematode parasite control of small ruminants in Malaysia, where anthelmintic resistance is now a major problem.

Animal Feed↗
PubMed1997

Evaluation of the fungus Beauveria bassiana as a potential biological control agent against phlebotomine sand flies in Colombian coffee plantations.

In Colombia, the entomopathogenic fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes) is widely used to control the coffee berry borer Hypothenemus hampei (Coleoptera: Scolytidae) in coffee plantations. Recent studies suggested that this fungus is also pathogenic to several important vectors of disease, including Phlebotomus papatasi and Lutzomyia longipalpis (Diptera: Psychodidae). The present study evaluated the use of B. bassiana as a potential biological control agent against phlebotomine sand flies in Colombian coffee plantations. Histopathologic examination indicates that B. bassiana is unable to infect sand flies under natural conditions, although dead sand flies were shown to be readily infected. In addition, laboratory bioassays where flies were exposed to the fungus applied onto coffee plants (though not filter paper) showed lower mean survival times than the control.

Animals↗
PubMed2000

Mass rearing the weevil Hylobius transversovittatus (Coleoptera: Curculionidae), biological control agent of Lythrum salicaria, on semiartificial diet.

Lythrum salicaria L., purple loosestrife, an invasive Eurasian perennial, is degrading wetlands across temperate North America. Chemical, physical, and mechanical methods failed to provide long-term control. Therefore, four host-specific insect species (two leaf feeders, a root feeder, and a flower feeder) were introduced as biological control agents. To increase the availability of adults of the root feeding weevil Hylobius transversovittatus Goeze for field releases, we developed a semiartificial diet. Suitability of different diet formulations (varying vitamin mixes, salt mixes, antimicrobials, water content, root content) and temperatures for larval development were evaluated. We also monitored how rearing on artificial diet and the number of larvae per container affected larval development time, larval survival, adult weight, and incidences of deformities. Rearing larvae on artificial diet reduced development time from 1-2 yr to 2-3 mo. Larval development was fastest and survival rates highest under constant temperatures of 25 degrees C. Hatch rate and larval survival decreased if eggs were surface sterilized. Using FABCO antimicrobials could not prevent fungal contamination; use of methyl paraben and sorbic acid was successful in suppressing fungal and bacterial growth throughout larval development time to <10%. The moisture content of the diet did not significantly affect larval survival, development, or adult weight. Decreasing the proportion of purple loosestrife roots in the diet reduced adult weight and the proportion of larvae completing development, and increased development time; no larvae were able to complete development in root-free diet. With an increase in the number of larvae per cup, survival rates were reduced. The experiments revealed a female biased sex ratio: females consistently developed faster and were heavier than males. Incidence of adult deformities was consistently below 5%. Increased availability of adults for field release as a result of mass production using the semiartificial diet will accelerate the biocontrol program targeting purple loosestrife. We are able to produce several hundred weevils per week and have adapted the diet to rear other root-feeding weevils.

Animals↗
PubMed2002

Possible application of a nematophagous fungus as a biological control agent of parasitic nematodes on commercial sheep farms in South Africa.

Biological control of parasitic nematodes of livestock is currently under development and represents another tool that may be integrated into helminth parasite control strategies. This paper presents a brief introduction to commercial sheep farming in South Africa and currently available nematode parasite control methods. These include the FAMACHA clinical assay, strategies of pasture management, dilution of resistant worm species by introduction of susceptible worms, breed resistant sheep and nutritional supplementation. The purpose of this paper is to outline the principles of biological control using nematophagous fungi and how it may be applied on sheep farms in South Africa.

Animal Husbandry↗
PubMed2001

Phytoseiid predators as potential biological control agents for Bemisia tabaci.

Mites of the family Phytoseiidae are known to be predators of whiteflies in several agroecosystems, especially of Bemisia tabaci Gennadius, a pest with high resistance to chemical insecticides that occurs in greenhouses in temperate regions. We collected predatory mites that were found to co-occur with whiteflies in the Middle East for control of B. tabaci: Tvphlodromus athiasae (Porath and Swirski), Neoseiulus barkeri Hughes, Tvphlodromips swirskii (Athias-Henriot), Euseius scutalis (Athias-Henriot), Phytoseius finitimus Ribaga. As a first step in the evaluation of these species as biological control agents, we measured their life-history traits when feeding on whiteflies. The intrinsic rates of increase (rm) of the predatory mite species ranged between 0.131 and 0.215 per day and E. scutalis had the highest rm estimated. Comparisons with the rm of B. tabaci indicate that some of the species should be capable of suppressing local populations of whitefly. The ability of predators to use alternative food was also tested, since it facilitates the setup of mass cultures and it can promote their persistence in the crop, even if the prey is scarce. All predatory mite species tested were able to survive and reproduce on a diet of broad bean pollen.

Animals↗
PubMed1996

Characterization of a genomic locus required for synthesis of the antibiotic 2,4-diacetylphloroglucinol by the biological control agent Pseudomonas fluorescens Q2-87.

The antibiotic 2,4-diacetylphloroglucinol (Phl) is an important factor in the biological control by fluorescent Pseudomonas spp. of many soilborne diseases including take-all disease of wheat. A 6.5-kb genomic DNA fragment from Pseudomonas fluorescens Q2-87 conferred production of Phl and of a red pigment distinct from Phl, but which typically is present when Phl is produced, upon all of 13 Phl-nonproducing recipient Pseudomonas strains into which it was introduced. Larger fragments that included flanking DNA sequences did not transfer this capability, suggesting that they contain negative regulatory element(s). Analysis of the 6.5-kb fragment by Tn3HoHo1 mutagenesis further localized the sequences required for Phl production to a segment of approximately 5 kb and revealed the presence of at least two divergently oriented transcriptional units. Insertions within the smaller unit or within about 3 kb of the 5' end of the larger unit caused loss of production of both Phl and the red pigment. Other insertions within the distal 1.5 kb of the larger transcriptional unit abolished production of only the red pigment. Pleiotropic changes in secondary metabolism or colony morphology were not observed in Pseudomonas strains containing the 6.5-kb fragment, although some Phl-producing derivatives grew more slowly and gave rise to smaller colonies than did the wild-type parental strains. The size of the genomic region involved in Phl production, and the consistency and specificity with which these sequences transferred Phl biosynthetic capability, support the conclusion that the 6.5-kb fragment contains the Phl biosynthetic locus.

Anti-Bacterial Agents↗
PubMed2001

Development of a strain-specific SCAR marker for the detection of Trichoderma atroviride 11, a biological control agent against soilborne fungal plant pathogens.

The genus Trichoderma includes biocontrol agents (BCAs) effective against soilborne plant pathogenic fungi. Several potentially useful strains for biological control are difficult to distinguish from other strains of Trichoderma found in the field. So, there is a need to find ways to monitor these strains when applied to natural pathosystems. We have used random amplified polymorphic DNA (RAPD) markers to estimate genetic variation among sixteen strains of the species T. asperellum, T. atroviride, T. harzianum, T. inhamatum and T. longibrachiatum previously selected as BCAs, and to obtain fingerprinting patterns. Analysis of these polymorphisms revealed four distinct groups, in agreement with previous studies. Some of the RAPD products generated were used to design specific primers. Diagnostic PCR performed using these primers specifically identify the strain T. atroviride 11, showing that DNA markers may be successfully used for identification purposes. This SCAR (sequence-characterised amplified region) marker can clearly distinguish strain 11 from other closely related Trichoderma strains.

Genetic Markers↗
PubMed2003

Taxonomic positioning of two biological control agents for plant diseases as Lysobacter enzymogenes based on phylogenetic analysis of 16S rDNA, fatty acid composition and phenotypic characteristics.

AIMS: To taxonomically position two bacterial strains conferring biological control activity towards plant diseases. METHODS AND RESULTS: Key phenotypic characteristics, including gliding motility and a high percentage of G + C content, indicated biocontrol strains N4-7 and C3 were essentially identical to those described for Lysobacter enzymogenes. Cellular fatty acid analysis confirmed a close relatedness of strains N4-7 and C3 to L. enzymogenes and a more distant relatedness to L. antibioticus. The 16S rDNA phylogenetic analysis revealed a distinct Lysobacter clade that included both strains within the gamma-proteobacteria. CONCLUSIONS: The combined taxonomic methods provide clear evidence that N4-7 and C3 should be grouped as strains of L. enzymogenes and not Stenotrophomonas maltophilia or a novel taxon. Phylogenetic analysis of 16S rDNA formed a Lysobacter clade that included several other environmentally diverse bacterial strains obtained from databases and confirmed relatedness of strains N4-7 and C3 to L. enzymogenes. SIGNIFICANCE AND IMPACT OF THE STUDY: Inclusion of N4-7 and C3 as strains of L. enzymogenes is among the first description of members of this genus as biocontrol agents of plant diseases. These results suggest that members of the Lysobacter group might provide a new source as plant-associated microbes that display biocontrol activity.

Bacterial Typing Techniques↗
PubMed2002

Antipredator defense of biological control agent Oxyops vitiosa is mediated by plant volatiles sequestered from the host plant Melaleuca quinquenervia.

The weevil Oxyops vitiosa is an Australian species imported to Florida, USA, for the biological control of the invasive weed species Melaleuca quinquenervia. Larvae of this species feed on leaves of their host and produce a shiny orange secretion that covers the integument. When this secretion is applied at physiological concentrations to dog food bait, fire ant consumption and visitation are significantly reduced. Gas chromatographic analysis indicates that the larval secretion qualitatively and quantitatively resembles the terpenoid composition of the host foliage. When the combination of 10 major terpenoids from the O. vitiosa secretion was applied to dog food bait, fire ant consumption and visitation were reduced. When these 10 terpenoids were tested individually, the sesquiterpene viridiflorol was the most active component in decreasing fire ant consumption. Fire ant visitation was initially (15 min after initiation of the study) decreased for dog food bait treated with viridiflorol and the monoterpenes 1,8-cineole and alpha-terpineol. Fire ants continued to avoid the bait treated with viridiflorol at 18 microg/mg dog food for up to 6 hr after the initiation of the experiment. Moreover, ants avoided bait treated with 1.8 microg/mg for up to 3 hr. The concentrations of viridiflorol, 1,8-cineole, and alpha-terpineol in larval washes were about twice that of the host foliage, suggesting that the larvae sequester these plant-derived compounds for defense against generalist predators.

Adaptation, Physiological↗
PubMed2003

Dietary influences on terpenoids sequestered by the biological control agent Oxyops vitiosa: effect of plant volatiles from different Melaleuca quinquenervia chemotypes and laboratory host species.

The weevil Oxyops vitiosa is an Australian species imported to Florida, USA, for the biological control of the invasive species Melaleuca quinquenervia. The larvae of this species feed on the leaves of their host and produce a shiny orange secretion that covers their integument. Previous results indicated that a major component of this secretion, viridiflorol, is sequestered from the host plant and repels a generalist predator, the red imported fire ant, Solenopsis invicta. When the larvae fed on a different chemotype of M. quinquenervia, which lacked viridiflorol but was rich in a different sesquiterpene, (E)-nerolidol, similar protection occurred. Solvent washes of these larvae indicated that (E)-nerolidol was sequestered from M. quinquenervia leaves and repelled S. invicta workers when applied to dog food baits at physiological concentrations (17.5, 35.0, and 52.5 microg/mg). Additionally, beta-caryophyllene also repelled S. invicta workers when applied to dog food baits at concentrations that approximated those in the O. vitiosa larval secretions (3.5 and 35 microg/mg). When the O. vitiosa larvae were fed leaves from laboratory hosts (nonfield hosts), similar repellent activity was found. This activity was traced to several of the same compounds (e.g., 1,8-cineole, viridiflorol) found to be active in their field host M. quinquenervia. These weevil larvae are opportunistic, sequestering the primary terpenoids in their host leaves that confer antipredator activity.

Animals↗
PubMed1983

[Biological control agents against mosquitoes].

The control programs of mosquitoes are physical; chemical, mechanic control, control by sterilization, genetic, public health rules and biological control. Biological control is the most efficient and convenient one because of resistant organisms against insecticides, economic problems and degeneration of the eco-system. This control employs protozoal, fungal, bacterial pathogens, mosquito predator fish, nematoda parasites as bioagents. Safety tests, sensitivity to environmental factors, effectiveness against non-target organisms, production, stability and field trials are all giving promising results.

Culicidae↗
PubMed2005

Biological control agent of common scab disease by antagonistic strain Bacillus sp. sunhua.

AIMS: To identify an antagonistic strain against Streptomyces scabiei and to characterize the antibiotic agent. The efficacy of the isolated strain in controlling common scab disease was also evaluated. METHODS AND RESULTS: A bacterial strain antagonistic against S. scabiei was isolated from the soil of a potato-cultivating area. This bacterium was identified as a Bacillus species by 16S rRNA gene sequence analysis and was designated Bacillus sp. sunhua. Antibiotics produced by this strain were proven to be stable within a broad pH range and at high temperatures. The culture broth was extracted with ethyl acetate, and then the crude extract was applied to HPLC. Two compounds were isolated and identified as iturin A and macrolactin A by 1H-NMR, 13C-NMR, HMBC, HMQC and mass spectrometer. The culture broth of Bacillus sp. sunhua had a suppressive effect on common scab disease in a pot assay, decreasing the infection rate from 75 to 35%. This strain also suppressed Fusarium oxysporum, the pathogen of potato dry rot disease. CONCLUSIONS: Bacillus sp. sunhua was shown to inhibit S. scabiei effectively. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report demonstrating that macrolactin A and iturin A inhibit S. scabiei. This study demonstrated the possibility of controlling potato scab disease using Bacillus sp. sunhua.

Anti-Bacterial Agents↗
PubMed2002

Modelling population dynamics of Orius laevigatus and O. albidipennis (Hemiptera: Anthocoridae) to optimize their use as biological control agents of Frankliniella occidentalis (Thysanoptera: Thripidae).

ORIUS LAEVIGATUS: (Fieber) and O. albidipennis (Reuter) play an important role in the control of Frankliniella occidentalis (Pergande) in crops and natural vegetation in the Mediterranean area. The biological parameters of the two anthocorids were studied and modelled in relation to temperature to optimize their use in thrips control programmes. Development times and reproductive parameters of O. laevigatus and O. albidipennis were determined at 20, 25, 30 and 35 degrees C. Pre-imaginal development times ranged from 34.6 and 37.2 days at 20 degrees C to 12.3 and 10.2 days at 35 degrees C in O. laevigatus and O. albidipennis, respectively. The lower thermal development threshold was significantly higher for O. albidipennis (14.2 +/- 0.9 degrees C) than for O. laevigatus (11.3 +/- 0.7 degrees C). No significant differences in fecundities between the two anthocorids were observed at 20, 25 and 30 degrees C. At 35 degrees C, O. albidipennis had a significantly higher fecundity than O. laevigatus. Non-linear models were used to explain reproduction and female survivorship in relation to temperature. The upper reproductive thresholds were estimated at 40.9 +/- 0.3 and 35.5 +/- 0.1 degrees C for O. albidipennis and O. laevigatus, respectively. The different optimum temperatures may explain, at least in part, the different distributions of the two species in the Palaeartic region and their population dynamics in greenhouses and natural vegetation in the south of Spain. The estimation of rm as a function of temperature showed high variability between years. Three release rates of 0.75-0.25 Orius per plant are recommended from early March to mid May to deal with thrips outbreaks in pepper crops.

Animals↗