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PubMed2001

Population dynamics of the white wax scale, Ceroplastes destructor (Hemiptera: Coccidae), on citrus in South Africa, with implications for biological control.

The population dynamics of the white wax scale, Ceroplastes destructor Newstead, was studied intensively in four easy-peel citrus orchards in the Western Cape Province of South Africa over three consecutive years (1997-1999). Key factor analysis was used to determine and quantify the contribution of individual mortality factors to the total generation mortality. Key stage mortality, determined from a cohort life table, was in the third instar and pre-ovipositing female stages. Mortality of C. destructor was caused primarily by parasitoids, predators and miscellaneous factors. Parasitoids and miscellaneous factors acted as density-dependent regulatory agents during the pre-ovipositional and first instar stages respectively. This has implications for biological control of C. destructor. Some of the mortality factors acted either randomly with no reference to the population densities or in an inverse density-dependent manner during the egg-crawler, second or third instar stages.

Animals↗

PubMedDate not supplied

[Beetles as biological agents in fly control].

309 beetles of 11 species were collected in Apsheron and other regions of Azerbaijan on sites polluted by animal and human feces to study the feasibility of using them as biological agents for flies' control. Two beetle species--S. planus and B. lethifers pterotapha belonging to the Carabidae and Tenebrionidae families--turned out to be predators which could destroy the larva of L. sericata flies under experimental conditions.

Animals↗

PubMed1981

Biological control of the snail intermediate hosts of human Schistosoma spp.: a review of its present status and future prospects.

The biological control of freshwater snail hosts of schistosome parasites has attracted much attention in recent years, but the efficiency of such bio-control agents has rarely been tested outside laboratory conditions. The present paper attempts to summarize the present status of biological control of snails intermediate hosts, to indicate some major gaps in our knowledge of this subject, especially those of a practical kind and, not least, to identify studies and activities which apparently merit priority for further sponsorship and support.

Animals↗

PubMed2001

Bt toxin resistance from loss of a putative carbohydrate-modifying enzyme.

The development of resistance is the main threat to the long-term use of toxins from Bacillus thuringiensis (Bt) in transgenic plants. Here we report the cloning of a Bt toxin resistance gene, Caenorhabditis elegans bre-5, which encodes a putative beta-1,3-galactosyltransferase. Lack of bre-5 in the intestine led to resistance to the Bt toxin Cry5B. Wild-type but not bre-5 mutant animals were found to uptake toxin into their gut cells, consistent with bre-5 mutants lacking toxin-binding sites on their apical gut. bre-5 mutants displayed resistance to Cry14A, a Bt toxin lethal to both nematodes and insects; this indicates that resistance by loss of carbohydrate modification is relevant to multiple Bt toxins.

Amino Acid Sequence↗

PubMed2005

Response of multiple seeded cocklebur and other cocklebur types to herbicide treatment.

Multiple seeded cocklebur has been found in the last decade in Texas, and described as a biotype of Xanthium strumarium L with up to 25 seeds per bur instead of the usual two. The multiple seeded bur typically produces up to nine seedlings, causing concern that it may be harder to control than normal seeded common cocklebur. The efficacies of a series of fungal and conventional commercial herbicides have been compared in the greenhouse on seedlings of multiple seeded cocklebur from Texas (MSC-TX) and normal common cockleburs from Texas (NCC-TX), Arkansas (NCC-AR), Illinois (NCC-ILL) and two from Mississippi (NCC-MS#1, NCC-MS#2). Three measures of herbicidal activity (reductions in plant height and dry weight, and mortality) were used. The fungal herbicide Alternaria helianthi (Hansf) Tubaki & Nishihara at 1 x 10(5) conidia ml(-1) + 2 g liter(-1) Silwet L-77 with an 8-h dew period was an effective herbicide with all biotypes, as were the commercial chemical herbicides chlorimuron (14.8 g ha(-1)), imazaquin (29.6 g ha(-1)), sodium hydrogen methylarsonate (MSMA; 279.1 g ha(-1)) and imazethapyr (39.5 g ha(-1)). The membrane-disrupting organic arsenical MSMA was effective with all biotypes, whereas commercial chemical herbicides which act by inhibiting branched-chain amino acid synthesis (chlorimuron, imazaquin and imazethapyr) were less effective against normal seeded common cocklebur biotypes with short stature. These studies showed that multiple seeded cocklebur was at least as susceptible to the biological agent A helianthi and to the conventional commercial herbicides studied as were normal seeded cockleburs, suggesting that existing methods should be adequate to control this novel biotype.

Alternaria↗

PubMed2000

Environmental biotechnology.

There is an increasing interest in environmental biotechnology owing to a worldwide need to feed the world's growing population and to maintain clean soil, air and water. The major technological developments are in plant and microbial biology. Plants can be more readily engineered for resistances that enhance yield or produce new products whereas microorganisms are exploited for their catalytic diversity and ease of genetic engineering.

Biotechnology↗

PubMed2004

Combining plant- and soil-dwelling predatory mites to optimise biological control of thrips.

The efficiency of a natural enemy combination compared to a single species release for the control of western flower thrips (WFT) Frankliniella occidentalis (Pergande) on cucumber plants was investigated. Since a large part of F occidentalis seems to enter the soil passage, a joint release of the plant-inhabiting predatory mite Amblyseius cucumeris (Oudemans) that feeds on thrips first-instar larvae and the soil-dwelling predatory mite Hypoaspis aculeifer (Canestrini) that preys on thrips pupae in the ground might offer a promising approach for a holistic control strategy. Therefore, two sets of experiments were conducted in cooperation with a commercial vegetable grower where the plants in plots were infested with a defined number of larval and adult F occidentalis. Two species of natural enemies were released either synchronously or solely, and their efficacy was compared to control plots devoid of antagonists. In both experiments, the predatory mites were released twice with a density of 46 A. cucumeris/m2, and 207 H. aculeifer/m2 (low-density) in the first experiment and 528 H. aculeifer/m2 (high-density) in the second one. Population growth of all arthropod species on the plants and in the soil was quantified at regular intervals and included all soil-dwelling mites and alternative preys present in the substrate. The results showed that H. aculeifer alone had a significant impact on thrips population development only when released at high-densities, but competence was lower compared to the other antagonist treatments. The impact of A. cucumeris alone and A. cucumeris & H. aculeifer combined was similar. Thus, the pooled exploitation of natural enemies did not boost thrips control compared to the single species application of A. cucumeris (non-additive effect), which could be explained by resource competition between both predatory mite species. Species number and population size in the soil of the experimental plots both showed a high variability, a possible consequence of their interaction with released soil-dwelling predatory H. aculeifer mites. The impact of resource competition and presence of alternative preys on thrips biological control is exhaustively discussed. From our study, we can extract the subsequent conclusions: (1) the combined use of H. aculeifer and A. cucumeris cannot increase thrips control on cucumber compared to the release of A. cucumeris alone, but the overall reliability of thrips biological control might be enhanced, (2) the availability of alternative preys seemed to affect the thrips predation rate of H. aculeifer, and (3) the impact of naturally occurring soil predatory mites on the control of WFT seemed to be partial.

Animals↗

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↗

PubMed2003

[Identification on an antagonistic rhizobacterium X3 from rhizosphere of cucumber].

Classical physiological and biochemical methods, Biolog, and 16S rDNA analysis were used to identify the strain X3 which could control cucumber seedling damping-off. Physiological and biochemical identification showed that it belonged to Pseudomanas aeruginosa, but Biolog identification showed it was P. spinosa. 16S rDNA determination and analysis was used for further identification, which showed that the 16S rDNA sequence of X3 shared 93.7% homologies with published sequence of P. aeruginosa from GenBank, and both sequences constituted a branch in Phylogenetic tree. Based on these results, it is considered that the strain X3 belongs to one strain of P. aeruginosa.

Base Sequence↗

PubMed1995

The sigma factor sigma s affects antibiotic production and biological control activity of Pseudomonas fluorescens Pf-5.

Pseudomonas fluorescens Pf-5, a rhizosphere-inhabiting bacterium that suppresses several soilborne pathogens of plants, produces the antibiotics pyrrolnitrin, pyoluteorin, and 2,4-diacetylphloroglucinol. A gene necessary for pyrrolnitrin production by Pf-5 was identified as rpoS, which encodes the stationary-phase sigma factor sigma s. Several pleiotropic effects of an rpoS mutation in Escherichia coli also were observed in an RpoS- mutant of Pf-5. These included sensitivities of stationary-phase cells to stresses imposed by hydrogen peroxide or high salt concentration. A plasmid containing the cloned wild-type rpoS gene restored pyrrolnitrin production and stress tolerance to the RpoS- mutant of Pf-5. The RpoS- mutant overproduced pyoluteorin and 2,4-diacetyl-phloroglucinol, two antibiotics that inhibit growth of the phytopathogenic fungus Pythium ultimum, and was superior to the wild type in suppression of seedling damping-off of cucumber caused by Pythium ultimum. When inoculated onto cucumber seed at high cell densities, the RpoS- mutant did not survive as well as the wild-type strain on surfaces of developing seedlings. Other stationary-phase-specific phenotypes of Pf-5, such as the production of cyanide and extracellular protease(s) were expressed by the RpoS- mutant, suggesting that sigma s is only one of the sigma factors required for the transcription of genes in stationary-phase cells of P. fluorescens. These results indicate that a sigma factor encoded by rpoS influences antibiotic production, biological control activity, and survival of P. fluorescens on plant surfaces.

Amino Acid Sequence↗

PubMed1987

Differential effects of Bacillus sphaericus strain 2362 on Culex quinquefasciatus and its competitor Culex cinereus in West Africa.

The larval susceptibility to Bacillus sphaericus strain 2362 of the non-man-biting mosquito Culex cinereus and the urban filariasis vector Culex quinquefasciatus, two competitor mosquitoes in polluted habitats, was compared. In the laboratory, both species ingested a similar amount of B. sphaericus spores when fed c. 2 x 10(5) spores per ml for 30 min. However, in the same experiment, third-instar larvae of Cx quinquefasciatus were reduced by 98% at 24 h exposure while Cx cinereus larvae were only reduced by 6% at 72 h. In the field, preimaginal populations of Cx cinereus ingested, within a week, more than 99% of the applied spores, but showed no significant decrease through 14 days in cesspools treated at 10 g/m2 of a flowable concentrate of B. sphaericus 2362, containing 2 x 10(10) spores/g. It is proposed that specific biological control of Cx quinquefasciatus could result from appropriate treatment of breeding-sites with larvicidal B. sphaericus and competitive displacement by Cx cinereus or other mosquitoes with larvae that are more tolerant of B. sphaericus.

Africa, Western↗

PubMed1997

Extended screening by PCR for seven cry-group genes from field-collected strains of Bacillus thuringiensis.

An extended multiplex PCR method was established to rapidly identify and classify Bacillus thuringiensis strains containing cry (crystal protein) genes toxic to species of Lepidoptera, Coleoptera, and Diptera. The technique enriches current strategies and simplifies the initial stages of large-scale screening of cry genes by pinpointing isolates that contain specific genes or unique combinations of interest with potential insecticidal activities, thus facilitating subsequent toxicity assays. Five pairs of universal primers were designed to probe the highly conserved sequences and classify most (34 of about 60) genes known in the following groups: 20 cry1, 3 cry2, 4 cry3, 2 cry4, 2 cry7, and 3 cry8 genes. The DNA of each positive strain was probed with a set of specific primers designed for 20 of these genes and for cry11A. Twenty-two distinct cry-type profiles were identified from 126 field-collected B. thuringiensis strains. Several of them were found to be different from all published profiles. Some of the field-collected strains, but none of the 16 standard strains, were positive for cry2Ac. Three standard and 38 field-collected strains were positive by universal primers but negative by specific primers for all five known genes of cry7 and cry8. These field-collected strains seem to contain a new gene or genes that seem promising for biological control of insects and management of resistance.

Animals↗

PubMed1989

Control of schistosomiasis in the Gezira.

For the control of schistosomiasis in irrigated agricultural schemes, the inhabitants must have:- 1) Enough potable water. 2) Latrines. 3) Proper health education to motivate the community to participate in the control. 4) Proper diagnostic facilities. 5) Proper available chemotherapy. 6) Focal mullusciciding. 7) If possible trial of biological and environmental methods of control. Following the above methods, we could reduce the prevalence of schistosomiasis from over 50% to about 13%. The important achievement, is the improvement of the health of the community; therefore more production and reduced morbidity and mortality.

Animals↗

PubMed2001

The distribution of Biomphalaria spp. in different habitats in relation to physical, biological, water contact and cognitive factors in a rural area in Minas Gerais, Brazil.

A total of 256 sites in 11 habitats were surveyed for Biomphalaria in Melquiades rural area (State of Minas Gerais) in August and November 1999 and in March 2000. Of the 1,780 Biomphalaria collected, 1,721 (96.7%) were B. glabrata and 59 (3.3%) B. straminea. Snails were found in all habitats except in wells, with the largest mean numbers in tanks, seepage ponds and canals, and the smallest numbers in springs, rice fields and fishponds. People's knowledge of the occurrence of Biomphalaria at the collection sites and the presence of Biomphalaria ova were strongly correlated with the occurrence of snails, and distance between houses and collection sites, as well as water velocity were inversely correlated with Biomphalaria occurrence (p < 0.001). The strongest predictor o f Biomphalaria occurrence was the presence of tilapia fish in fishponds. Fourteen Biomphalaria (0.8% of all snails) found at 6 sites were infected with Schistosoma mansoni. Suggestions are made for the utilization of local people's knowledge in snail surveys and further studies are recommended on the possible use of tilapia for biological control of Biomphalaria in fishponds, as well as modeling of S. mansoni transmission and reinfection.

Animals↗

PubMed2004

Pre-germinated conidia of Coniothyrium minitans enhances the foliar biological control of Sclerotinia sclerotiorum.

The relatively slow germination rate of Coniothyrium minitans limits its control efficiency against Sclerotinia sclerotiorum. Pre-germinated conidia of C. minitans enhanced its efficiency significantly: in foliar experiments with oilseed rape, hyphal extension of S. sclerotiorum was inhibited by 68%, while formation of sclerotia was completely inhibited when pre-germinated conidia were applied.

Ascomycota↗

PubMed2001

Infiltration of a Hawaiian community by introduced biological control agents.

To examine the community-wide effects of introduced biocontrol agents on Kauai Island, Hawaii, we constructed quantitative food webs showing interactions among plants, moths, and moth parasitoids in a native forest. Eighty-three percent of parasitoids reared from native moths were biological control agents, 14% were accidental immigrants, and 3% were native species. Although parasitism by biological control agents reached 28% in some species of moth, all biocontrol agents reared had been released before 1945. This study highlights the importance of considering the potential damage caused by an introduced control agent, in addition to that caused by the target alien species.

Animals↗

PubMed1984

Vector control of snail-mediated human trematode infections.

Inspite of the recent general acceptance of the use of safe and effective chemotherapeutic drugs in the treatment of major human trematode infections, vector control e.g. control of the snail intermediate host will continue to play an important role in programmes for controlling schistosomiasis, clonorchiasis, opisthorchiasis and paragonimiasis. The main vector control measures are: a) use of chemical pesticides or molluscicides and plants showing molluscicidal properties; b) biological control through introduction of competitor species or natural enemies of snails; c) alteration of the environment either by application of one or a combination of the following; drainage, filling, ponding, clearing of vegetation and regulation of use of water for agricultural purposes.

Animals↗

PubMed1993

Prospects for the use of larvivorous fish for malaria control in Ethiopia: search for indigenous species and evaluation of their feeding capacity for mosquito larvae.

Because of problems with drug and insecticide resistance, the National Organization for the Control of Malaria and other Vectorborne Diseases, Ethiopia, has embarked on a programme of research on alternative malaria control methods, including the use of biological control agents, such as larvivorous fish. The objectives of the study were to identify indigenous larvivorous fish species which could be potential candidates for use as biological control agents; to extend knowledge of their distribution in Ethiopia; and to conduct laboratory tests to determine their feeding capacity. An extensive search resulted in the identification of 11 larvivorous fish species indigenous to Ethiopia, including five species previously unrecorded in the country. Seven species were assessed under standard laboratory conditions for their feeding capacity on larvae of Anopheles gambiae s.l. and Culex andersoni. All species tested were efficient larvivores in the laboratory. However, their larvivorous capacity should be tested further in field trials. Based on the findings of this study, two priority areas for the assessment of biological control using larvivorous fish were identified, the port city of Assab, using the local species Aphanius dispar, and the Ogaden, south-eastern Ethiopia, using the local species Oreochromis spilurus spilurus.

Animals↗