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PubMed2005

Development of a Bacillus sphaericus tablet formulation and its evaluation as a larvicide in the biological control of Culex quinquefasciatus.

This study aimed to analyze the final fermentation culture of Bacillus sphaericus 2362, standardize it and develop an active tablet formulation for use in urban mosquito breeding sites. It was performed in three phases: analysis and standardization of a B. sphaericus fermented culture; physical, chemical, and biological analysis of the active powder (solubility, residual humidity, particle size, resting angle, flowing off time, compacted density, and biological activity against Culex quinquefasciatus larvae); and the development of fast-disintegrating tablets. Five formulations with differing compositions were developed and a UV protector was added to the selected formulation. The formulation products with or without UV protector, as well as the active powder caused 100% larval mortality from 1 day to 2 months after a single treatment under simulated field conditions. These results show that the UV protector does not affect the initial larvicide activity of B. sphaericus, nor its persistence over a period of two months.

Animals↗

PubMed2003

Cloning of biologically active genomes from a Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus isolate by using a bacterial artificial chromosome.

Purification of genotypes from baculovirus isolates provides understanding of the diversity of baculoviruses and may lead to the development of better pesticides. Here, we report the cloning of different genotypes from an isolate of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HaSNPV) by using a bacterial artificial chromosome (BAC). A transfer vector (pHZB10) was constructed which contained an Escherichia coli mini-F replicon cassette within the upstream and downstream arms of HaSNPV polyhedrin gene. Hz2e5 cells were co-transfected with wild-type HaSNPV DNA and pHZB10 to generate recombinant viruses by homologous recombination. The DNA of budded viruses (BVs) was used to transform E. coli. One of the bacmid colonies, HaBacHZ8, has restriction enzyme digestion profiles similar to an in vivo cloned strain HaSNPV-G4, the genome of which has been completely sequenced. For testing the oral infectivity, the polyhedrin gene of HaSNPV was reintroduced into HaBacHZ8 to generate the recombinant bacmid HaBacDF6. The results of one-step growth curves, electron microscopic examination, protein expression analysis and bioassays indicated that HaBacDF6 replicated as well as HaSNPV-G4 in vitro and in vivo. The biologically functional HaSNPV bacmids obtained in this research will facilitate future studies on the function genomics and genetic modification of HaSNPV.

Animals↗

PubMedDate not supplied

[Malaria in the Republic of Djibouti. Strategy for control using a biological antilarval campaign: indigenous larvivorous fishes (Aphanius dispar) and bacterial toxins].

The authors take stock of the present situation of malaria in the Republic of Djibouti which, after several decades of silence, seems to have been reintroduced at the beginning of the seventies. Actually it is hypo-endemic malaria with Plasmodium falciparum of which the only vector seems to be Anopheles arabiensis, gambiae complex. The specificity of the larvae nests allows a control strategy based on the only treatment of larvae sites by biological control: larvivorous fishes (Aphanius Dispar) and in addition the pin-point use of bacterial toxins as a complementary measure. The first results obtained in the rural zones around the capital are encouraging and permit to envisage the extensions of such a strategy to the whole of the territory of the Republic.

Africa, Eastern↗

PubMed1994

Biological control of fungal pathogens.

Biological control of soil-borne plant pathogens is a potential alternative to the use of chemical pesticides, which have already been proved to be harmful to the environment. Several strains of the fungus Trichoderma have been isolated and found to be effective biocontrol agents of various soil-borne plant pathogenic fungi under greenhouse and field conditions. Different application approaches have been used including integration of Trichoderma with reduced doses of chemical agents. Biochemical and molecular biology studies carried out to explore the mechanisms involved in biological control revealed that Trichoderma is a rather specific mycoparasite. Lectins were found to be involved in the recognition between Trichoderma and its host fungi, whereas chitinase is involved in the degradation of the host cell wall. Genetic engineering techniques were employed in order to increase the effectiveness, stability, and biocontrol capacity of Trichoderma spp. as well as other biocontrol agents, such as Pseudomonass spp. and Rhizobium.

Chitinases↗

PubMed2006

Mass rearing and egg release of Buenoa scimitra Bare as biocontrol of larval Culex quinquefasciatus.

Backswimmers have been recognized as the most promising predators of mosquito larvae. The aim of this investigation was to study mass rearing and egg release of Buenoa scimitra for the biological control of Culex quinquefasciatus Say. Among the most important results were that production of backswimmer eggs occurred for 263 days, and also that eggs were released in artificial containers with production of new individuals until the adult stage was obtained. In addition, a statistically significant reduction in mosquito larval density was observed on some sampling dates.

Animals↗

PubMed2005

A clp gene homologue belonging to the Crp gene family globally regulates lytic enzyme production, antimicrobial activity, and biological control activity expressed by Lysobacter enzymogenes strain C3.

Lysobacter enzymogenes strain C3, a biological control agent for plant diseases, produces multiple extracellular hydrolytic enzymes and displays antimicrobial activity against various fungal and oomycetous species. However, little is known about the regulation of these enzymes or their roles in antimicrobial activity and biocontrol. A study was undertaken to identify mutants of strain C3 affected in extracellular enzyme production and to evaluate their biocontrol efficacy. A single mini-Tn5-lacZ(1)-cat transposon mutant of L. enzymogenes strain C3 that was globally affected in a variety of phenotypes was isolated. In this mutant, 5E4, the activities of several extracellular lytic enzymes, gliding motility, and in vitro antimicrobial activity were reduced. Characterization of 5E4 indicated that the transposon inserted in a clp gene homologue belonging to the Crp gene family of regulators. Immediately downstream was a second open reading frame similar to that encoding acetyltransferases belonging to the Gcn5-related N-acetyltransferase superfamily, which reverse transcription-PCR confirmed was cotranscribed with clp. Chromosomal deletion mutants with mutations in clp and between clp and the acetyltransferase gene verified the 5E4 mutant phenotype. The clp gene was chromosomally inserted in mutant 5E4, resulting in complemented strain P1. All mutant phenotypes were restored in P1, although the gliding motility was observed to be excessive compared with that of the wild-type strain. clp mutant strains were significantly affected in biological control of pythium damping-off of sugar beet and bipolaris leaf spot of tall fescue, which was partially or fully restored in the complemented strain P1. These results indicate that clp is a global regulatory gene that controls biocontrol traits expressed by L. enzymogenes C3.

Acetyltransferases↗

PubMed1990

[A review of larvivorous fish].

Recently, because of concern about the effects of insecticide on the environment, increased attention is being given to the use of biological agents for controlling the vectors of human disease. Biological control may encompass the use of predators, pathogens, parasites, pheromones, insect growth regulators, and other factors. Of these agents only fish and bacteria have so far been used operationally in mosquito control. Since 1988 fish have been employed for controlling Aedes larvae in water containers in Liuchiu, Pingtung. A review of larvivorous fish (mainly Gambusia affinis) and the present status of the use of fish in mosquito control in Mainland China are thus made for ready reference for the workers in mosquito control in Taiwan.

Animals↗

PubMed2006

Molecular identification of Bacillus thuringiensis var. israelensis to trace its fate after application as a biological insecticide in wetland ecosystems.

AIMS: To determine the fate of viable Bacillus thuringiensis var. israelensis (Bti) spores dispersed in the environment, using a universally applicable molecular detection methodology. METHODS AND RESULTS: Soil samples were spread on growth medium, after a temperature selection of the spores. A PCR amplification of the cry4Aa and cry4Ba insecticidal genes was applied on the colonies. Ribotyping was performed subsequently. This combined molecular method proved to be very specific for Bti, which was easily differentiated from the other B. thuringiensis serovars. A site regularly treated with Vectobac-G was chosen within the 'Bolle di Magadino' natural reserve, and monitored throughout 1 year for the detection of Bti spores. The results showed that the numbers were relatively high after insecticidal applications (1.4 x 10(5) CFU g(-1)), and decreased approx. 10-fold after 220 days. A successive treatment induced a new increase. CONCLUSIONS: The results show that yearly repeated use of Vectobac-G does not seem to have a major ecological impact on the 'Bolle di Magadino' natural reserve. Bti spores followed a trend leading to their eventual disappearance from the ecosystem, despite the seasonal application of this biological insecticide for more than a decade. SIGNIFICANCE AND IMPACT OF THE STUDY: The molecular identification of Bti cells through the PCR analysis of the delta-endotoxins genes coupled to ribotyping, is an innovative method, that has enabled the identification of this organism into wetland environments.

Bacillus thuringiensis↗

PubMed1999

Induction of stable benomyl-tolerant phenotypic mutants of Trichoderma pseudokoningii MTCC 3011, and their evaluation for antagonistic and biocontrol potential.

Trichoderma pseudokoningii MTCC 3011 is a very useful strain for biological control of the plant pathogen Sclerotium rolfsii under post-harvest conditions. In the present investigation, several benomyl-tolerant phenotypic mutants of this strain have been generated using a two step mutagenesis-chemical followed by gamma irradiation. The mutants differed from the wild type strain in antibiotic and disease control potential. Some of the mutants are superior to the wild type in biocontrol potential on S. rolfsii.

Antifungal Agents↗

PubMedDate not supplied

Biological control of weeds: research by the United States Department of Agriculture-Agricultural Research Service: selected case studies.

Research by the USDA-Agricultural Research Service (ARS) on biological control of weeds has been practiced for many years because of its inherent ecological and economic advantages. Today, it is further driven by ARS adherence to Presidential Executive Order 13112 (3 February 1999) on invasive species and to USDA-ARS policy toward developing technology in support of sustainable agriculture with reduced dependence on non-renewable petrochemical resources. This paper reports examples or case studies selected to demonstrate the traditional or classical approach for biological control programs using Old World arthropods against Tamarix spp, Melaleuca quinquenervia (Cav) ST Blake and Galium spurium L/G aparine L, and the augmentative approach with a native plant pathogen against Pueraria lobata Ohwi = P montana. The examples illustrated various conflicts of interest with endangered species and ecological complexities of arthropods with associated microbes such as nematodes.

Agriculture↗

PubMed2003

Biological control of Fusarium wilt of pigeonpea Cajanus cajan (L.) Millsp with chitinolytic Alcaligenes xylosoxydans.

Alcaligenes xylosoxydans protected pigeonpea from Fusarium wilt in a pot experiment and field trials. When seeds of pigeonpea (C. cajan) were treated with A. xylosoxydans and sown in soil infested with Fusarium, the incidence of wilt was reduced by 43.5% and resulted in 58% higher grain yield. The antifungal activity of A. xylosoxydans was based on chitinase production and was comparable in efficacy to commercial antifungal agents such as benlate, monitor WP, thiram and bavistin.

Alcaligenes↗

PubMedDate not supplied

United States Department of Agriculture-Agricultural Research Service research programs in biological control of plant diseases.

A number of USDA-ARS programs directed at overcoming impediments to the use of biocontrol agents on a commercial scale are described. These include improvements in screening techniques, taxonomic studies to identify beneficial strains more precisely, and studies on various aspects of the large-scale production of biocontrol agents. Another broad area of studies covers the ecological aspects of biocontrol agents-their interaction with the pathogen, with the plant and with other aspects of the environmental complex. Examples of these studies are given and their relevance to the further development and expansion of biocontrol agents is discussed.

Agriculture↗

PubMed2002

Ecophysiology and breeding of mycoparasitic Trichoderma strains (a review).

Losses due to plant diseases may be as high as 10-20% of the total worldwide food production every year, resulting in economic losses amounting to many billions of dollars and diminished food supplies. Chemical control involves the use of chemical pesticides to eradicate or reduce the populations of pathogens or to protect the plants from infection by pathogens. For some diseases chemical control is very effective, but it is often non-specific in its effects, killing beneficial organisms as well as pathogens, and it may have undesirable health, safety, and environmental risks. Biological control involves the use of one or more biological organisms to control the pathogens or diseases. Biological control is more specialized and uses specific microorganisms that attack or interfere with the pathogens. The members of the genus Trichoderma are very promising against soil-born plant parasitic fungi. These filamentous fungi are very widespread in nature, with high population densities in soils and plant litters [1]. They are saprophytic, quickly growing and easy to culture and they can produce large amounts of conidia with long lifetime.

Antibiosis↗

PubMed1994

Larvivorous capacity of some indigenous fish of Haryana state.

Studies were undertaken to assess the role of some indigenous fish of Haryana state for the biological control of mosquitoes. Total of 28 fish species were encountered. Only six fresh water fish species Puntius ticto, Colisa fasciata, Aplocheilus panchax, Rasbora daniconius, Chanda nama, and Esomus danricus species possessed good feeding potential on mosquito larvae. The small size, well developed eyes and position of the mouth seem to be probably the important factors helping their voracity on mosquito larvae. These fish are either surface, subsurface or column feeders.

Animals↗

PubMed2003

Efficacy of Paecilomyces lilacinus (strain 251) for the control of root-knot nematodes.

The egg pathogenic fungus Paecilomyces lilacinus (strain 251), is a unique strain with a wide range of activity against the most important plant parasitic nematodes. Due to increased production capacity by solid state fermentation and a new water dispersible granule (WDG) formulation, this biological nematicide may be used in an integrated approach to control plant parasitic nematodes. Dose response experiments were conducted with the root-knot nematode Meloidogyne incognita on tomatoes using the new WDG formulation. The results revealed a clear correlation between rate applied and the degree of control concerning the reduction in damage to the root and multiplication of the nematode. Best control was achieved by applying the biological nematicide at rates of 2 to 4 times 10(9) conidia per plant as a soil treatment one week before planting. Monitoring the P. lilacinus population in the rhizosphere showed a decline after 2 to 3 month which can lead to insufficient control over a full growing season. Repeated application to maintain the antagonist population at a sufficient level could be used to secure long term control of root-knot nematodes.

Analysis of Variance↗

PubMed2005

Evaluation of various control agents against mosquito larvae in rice paddies in Taiwan.

A field test was conducted in rice paddies adjacent to Wufeng, Taichung County in Central Taiwan to evaluate the efficacy of control agents against mosquito larvae. The agents included Bacillus thuringienesis israelensis (Bti), two Lagenidium giganteum products (Lg product A and T), and temephos. The major mosquito species found in the rice paddies were Culex tritaeniorhynchus/vishnui and Anopheles sinensis. Compared to controls, a 7-day treatment with Bti or Lg products A and T caused overall reductions in the number of immatures (larvae and pupae) of Cx. tritaeniorhynchus/vishnui of 77.5%, 49.7%, and 21.9%, respectively, whereas temephos caused an increase of 66.9%. The overall reductions in An. sinensis were 85.4%, 8.6%, 44.6%, and 92.1%, respectively. There was no significant reduction in the number of mosquito larvae following 42 days of treatment with these agents. In summary, 1-week treatments with both biological control agents produced moderate overall reductions in mosquito larvae in rice paddies. The insecticide temephos, on the other hand, was very effective at suppressing the larvae of An. sinensis but significantly increased the number of Cx. tritaeniorhynchus/vishnui larvae in temephos-treated plots.

Animals↗

PubMed2006

Isolation and characterization of rhizosphere bacteria with potential for biological control of weeds in vineyards.

AIMS: Deleterious rhizosphere inhabiting bacteria (DRB) have potential to suppress plant growth. This project focuses on the isolation of DRB with potential for development as commercial products for weed control. METHODS AND RESULTS: Bacteria were isolated from the rhizosphere, rhizoplane, and endorhizosphere of seedlings and mature plants of wild radish (Raphanus raphanistrum), annual ryegrass (Lolium rigidum) and capeweed (Arctotheca calendula) growing in vineyards in the Swan Valley, Western Australia. A majority (81.5%) of the 442 strains was obtained from either rhizospheres or rhizoplanes. Rapid screening techniques were developed to evaluate in the laboratory and glasshouse the effects of bacteria on plants. Strains were screened in the glasshouse for deleterious effects on annual ryegrass, wild radish, grapevine rootlings (Vitis vinifera) and the legume cover crop subterranean clover (Trifolium subterraneum). Three strains were identified using the Biolog system and 16S rRNA gene sequencing as two strains of Pseudomonas fluorescens (WSM3455 and WSM3456) and one strain of Alcaligenes xylosoxidans (WSM3457). One of the P. fluorescens (WSM3455) strain produced hydrogen cyanide, an inhibitor of plant roots and a broad-spectrum antimicrobial compound. CONCLUSIONS: Three strains specifically inhibited wild radish but had no significant deleterious effects on either grapevine rootlings or subterranean clover. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggested manipulation of the weed seedling rhizosphere using identified DRB as a potential biocontrol agent for wild radish.

Bacteria↗

PubMed1984

Laboratory observations on Toxorhynchites splendens Wiedemann in Thailand.

The biology of Toxorhynchites splendens predaceous larvae which breed in domestic containers like Aedes aegypti was studied. Egg stage lasts 52.64 +/- 0.13 hours. There are four larval instars lasting 2.38 +/- 0.04, 1.24 +/- 0.26, 8.09 +/- 1.6 and 28.78 +/- 5.39 days respectively. Pupal development lasts 5.18 +/- 1.06 days. The adult life span is 29.55 +/- 8.06 days. Growth increment was by measuring the size of head capsule. Number of second instar prey larvae consumed by 1 to 4 instars predaceous larvae were 9.32 +/- 1.77, 5.94 +/- 1.11, 37.03 +/- 7.05 and 273.06 +/- 50.69 respectively. The fourth instar was very aggressive especially 2-3 days before pupation when it killed without eating them. The construction of biological life table indicated net reproductive of increase (R0) of 16.3, capacity for increase (rc) of 0.094, finite rate of increase (lambda) of 1.08 and mean duration of a generation (Tc) of 44.445 days. The mortality at the first and second larval instar was high and the calculated population index (I) was 14.81.

Aedes↗