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PubMed2005

Toxicity of Bacillus thuringiensis to parasitic and free-living life-stages of nematode parasites of livestock.

A collection of Bacillus thuringiensis (Bt) strains (Bts) were screened for activity against the free-living larval stages of nematode parasites of livestock. Two strains were identified with significant activity in inhibiting larval development of Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia circumcincta. These strains were also toxic to the adult parasitic stages of these nematode species in vitro. Adult H. contortus and O. circumcincta showed complete cessation of movement within 2 and 4 days, respectively. Trichostrongylus colubriformis adults were less affected, however, movement was still significantly reduced compared with controls. The in vitro activity against the larval stages was of a magnitude similar to or greater than that seen with the anthelmintic drugs thiabendazole and levamisole. N-terminal amino acid sequencing indicated that the two Bts contained either Cry5A and Cry5B proteins, or a Cry13 protein, and the presence of the corresponding cry5A, cry5B and cry13 genes was confirmed by PCR and sequencing. Bacillus thuringiensis spore-crystal suspensions exposed to acidic pH conditions (pH<or=3) showed greatly reduced toxicity in subsequent bioassays with nematode larvae, highlighting the need to protect the toxin from the acidic conditions of the sheep abomasum if it were to be administered per os as an anthelmintic. This study indicates that both the parasitic adult stages and the free-living larval stages of economically significant nematode parasites are susceptible to the effects of Bt, thus identifying this group of toxins as potential biocontrol agents.

Animals↗
PubMed1996

Induction of traps by Ostertagia ostertagi larvae, chlamydospore production and growth rate in the nematode-trapping fungus Duddingtonia flagrans.

Biological control of parasitic nematodes of domestic animals can be achieved by feeding host animals chlamydospores of the nematode-trapping fungus Duddingtonia flagrans. In the host faeces, D. flagrans develop traps that may catch nematode larvae. In experiments on agar, D. flagrans had a growth rate between 15 and 60 mm/week at temperatures between 20 and 30 degrees C. The presence of nematodes induces the fungus to produce traps. The rate of trap formation in D. flagrans has an optimum at 30 degrees C, producing 700-800 traps/cm2/2 days, when induced by 20 nematodes/cm2 on agar. Approaching 10 and 35 degrees C the ability to produce traps is gradually reduced. The response of chlamydospore production on agar to changes in temperature is the same as that for trap formation. On agar, at 10, 20 and 30 degrees C D. flagrans loses its trap inducibility after 2-3 weeks. During the ageing process, increasing numbers of chlamydospores are produced up to a certain limit. The time for reaching maximum chlamydospore concentration coincided with the time for loss of induction potential. The implications of these results in relation to biological control in faeces are discussed.

Animals↗
PubMed1986

Dispersal of the parasitic ciliate Lambornella clarki: implications for ciliates in the biological control of mosquitoes.

Lambornella clarki (Ciliophora: Tetrahymenidae), an endoparasite of Aedes sierrensis (Diptera: Culicidae), is dispersed by infected adult mosquitoes. Invasion of the ovaries induces parasitically castrated females to exhibit oviposition behavior and thereby actively disperse ciliates through deposition into water. Oviposition behavior of infected females is prolonged and mimics that of normal gravid females in their first gonotropic cycle. Adults of both sexes also passively disperse ciliates by dying on water surfaces, and infected adults are more likely to die on water than uninfected adults. Ciliates dispersed by infected adults can infect larvae and form desiccation-resistant cysts. Parasite-induced dispersal by hosts, desiccation-resistant cysts, an active host-seeking infective stage, and high infection and mortality rates all indicate significant biological control potential for these and related ciliates against container-breeding mosquitoes.

Aedes↗
PubMed1992

Predation of Biomphalaria and non-target molluscs by the crayfish Procambarus clarkii: implications for the biological control of schistosomiasis.

The North American crayfish Procambarus clarkii was examined under laboratory conditions for its ability to prey on Biomphalaria pfeifferi and B. glabrata, molluscan intermediate hosts of human schistosomiasis, and other, non-target gastropod species. Both male and female adult crayfish significantly reduced survival of neonate snails, even though alternative animal and plant foods were both available. In subsequent experiments, no differences in snail consumption were detected, for either adult or juvenile crayfish, in the presence or absence of a plant food alternative. Both adult and juvenile crayfish were able to consume small (2.5 mm) and large (17.5 mm) B. glabrata, suggesting that no size refuge from predation exists. Both adult and juvenile crayfish consumed Biomphalaria egg masses, although this consumption was significantly greater for juveniles. Procambarus clarkii adults were unable to consume substantial numbers of the relatively thick-shelled prosobranch snails Pila ovata and Lanistes carinatus. Crayfish did consume a third prosobranch, Melanoides tuberculata, and the pulmonate snail Physa acuta, but at a lower rate relative to consumption of Biomphalaria. Physa acuta, itself of North American origin, responded to the presence of crayfish by rapidly leaving the water and thereby avoided predation. Implications of these results for the biological control of schistosome-transmitting snails in East Africa are discussed.

Animals↗
PubMed1994

Expression of mosquitocidal toxin genes in a gas-vacuolated strain of Ancylobacter aquaticus.

A series of plasmids bearing the binary toxin genes of Bacillus sphaericus 2297 or 2317.3, the 100-kDa toxin gene of B. sphaericus SSII-1, or the 130-kDa (cryIVB) toxin gene of Bacillus thuringiensis subsp. israelensis were constructed and introduced into Ancylobacter aquaticus by electroporation. The transformed A. aquaticus cells exhibited significant toxicity towards mosquito larvae, demonstrating a potential use of recombinant A. aquaticus for biological control of mosquitoes.

Animals↗
PubMed2002

Wolbachia as a potential tool for suppressing filarial transmission.

There is currently a great deal of interest in Wolbachia because of their wide distribution in arthropods and filarial nematodes and their striking effects on the biology of their hosts, including a possible role in speciation. They manipulate the reproduction of arthropod hosts through various effects on their hosts' biology, particularly cytoplasmic incompatibility (CI), to increase the proportion of infected individuals in the population, often to the point of fixation. This ability of Wolbachia to sweep through host populations indicates several potential applications of Wolbachia in the control of mosquito-borne disease. One uses Wolbachia-induced CI as a form of sterile-insect technique, to suppress mosquito populations. Another envisages the application of CI for population replacement, with the intention of preventing the transmission of human pathogens, by substituting desirable genotypes, including those carried in transgenes. A third possibility is to use Wolbachia to reduce the survival of mosquito populations and thereby reduce their ability to transmit the infection. This article provides an overview of the biological effects of Wolbachia on arthropod hosts, with discussion of the possible future exploitation of these effects in the control of filariasis.

Animals↗
PubMedDate not supplied

Haematophagy and cleptohaematophagy of clerada apicicornis (Hemiptera: lygaeidae), a potential biological control agent of rhodnius prolixus (Hemiptera: reduviidae).

Because of its ability to prey on Triatominae in rural houses, Clerada apicicornis has been suggested as a potential biological control agent of Rhodnius prolixus. It has also been suggested as a potential vector of mammalian trypanosomes such as Trypanosoma cruzi, because of its ability to take blood directly from mammals. To help resolve these conflicting ideas, we assessed the haematophagic behaviour of C. apicicornis by carrying out feeding trials on laboratory animals. Cleptohaematophagic behaviour was also assessed by allowing C. apicicornis to feed on R. prolixus previously engorged with avian blood. The low proportion of blood meals taken directly from laboratory animals indicates a facultative haematophagy in this species, whereas a greater proportion of nymphs and adults were able to obtain vertebrate blood by predation on engorged R. prolixus. The results suggest that C. apicicornis is unlikely to be effective as a biological control agent, but is also unlikely to have a significant role in the transmission of vertebrate pathogens.

Animals↗
PubMed1970

Control methods for snail-borne zoonoses.

All trematodes which cause infections and diseases in humans (zoonoses) require snails for their first intermediate host. Some have additional intermediate hosts such as crustaceans, fishes and frogs. In this paper I have discussed the use of various procedures for controlling snail populations thereby reducing the population of trematodes whose cercariae penetrate the skin of man, or which are acquired by eating raw aquatic vegetation such as watercress, or which cause pathology in fish. Biological, chemical, and physical snail control techniques are discussed. The most promising molluscucides are copper compounds, Bayluscide, biocidal rubber and molluscicidal bait.

Animals↗
PubMed2001

Spinosad, a new tool for insect control in vegetables cultivated in greenhouses.

Spinosad is a biological insecticide derived as a fermentation product from the soil actinomycete Saccharopolyspora spinosa. The compound was tested for its possible use in northwestern Europe in vegetables cultivated in greenhouses. Spinosad is an insect control agent that has activity against a wide range of insect pests including caterpillars, leafminers and thrips. Because of its selectivity on a large number of beneficials used in greenhouses, spinosad is an interesting tool for insect control. A SC formulated product, containing 480 g a.i. litre-1, was tested in 1998, 1999 and 2000 in a range of trials at the research stations of Naaldwijk/Netherlands, and Gembloux/Belgium. This paper reviews and discusses the efficacy results on Trialeurodes vaporarium, Frankliniella occidentalis, Chrysodeixis Chalcites, Liriomyza Bryoniae. According the target insect rates from 4.8 till 36 g a.i./hl were tested. Consistent performance was recorded on F. occidentalis at rates of 9.6 g a.i./hl or above. Interesting efficacy results were recorded on the other above-mentioned insects.

Animals↗
PubMed2004

Symbioses of grasses with seedborne fungal endophytes.

Grasses (family Poaceae) and fungi of the family Clavicipitaceae have a long history of symbiosis ranging in a continuum from mutualisms to antagonisms. This continuum is particularly evident among symbioses involving the fungal genus Epichloe (asexual forms = Neotyphodium spp.). In the more mutualistic symbiota, the epichloe endophytes are vertically transmitted via host seeds, and in the more antagonistic symbiota they spread contagiously and suppress host seed set. The endophytes gain shelter, nutrition, and dissemination via host propagules, and can contribute an array of host fitness enhancements including protection against insect and vertebrate herbivores and root nematodes, enhancements of drought tolerance and nutrient status, and improved growth particularly of the root. In some systems, such as the tall fescue N. coenophialum symbioses, the plant may depend on the endophyte under many natural conditions. Recent advances in endophyte molecular biology promise to shed light on the mechanisms of the symbioses and host benefits.

Animals↗
PubMed2004

Steinernema glaseri Santa Rosa strain (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora CCA Strain (Rhabditida: Heterorhabditidae) as biological control agents of Boophilus microplus (Acari: Ixodidae).

The present study was carried out to evaluate the action of Steinernema glaseri Santa Rosa strain and Heterorhabditis bacteriophora CCA strain as biological control agents of Boophilus microplus. Engorged females ticks were distributed on Petri dishes containing different concentrations of infective juvenile (IJ) nematodes (0, 375, 500, 750, 1,500, 2,500, 5,000 and 25,000). The data showed a reduction of approximately 90% in the eggs laid at a concentration of 5,000 S. glaseri IJs and approximately 80% at a concentration of 1,500 H. bacteriophora IJs. The female mortality increased linearly with the increase in S. glaseri concentrations. However, in the tests with H. bacteriophora this linearity was not observed. The effectiveness of the treatment with both species of entomopathogenic nematodes was compatible with other control methods. The results show the potential of S. glaseri and H. bacteriophora as biological control agents for the control of B. microplus under laboratory conditions.

Animals↗
PubMed1992

Biological control of Culicidae with the copepod Mesocyclops aspericornis and larvivorous fish (Poeciliidae) in a village of French Polynesia.

The copepod Mesocyclops aspericornis Daday and the larvivorous fishes Gambusia affinis (B. & G.) and Poecilia reticulata R. & B., were released into mosquito breeding sites in Tuherahera village, Tikehau atoll, French Polynesia, to control larvae of Aedes aegypti (L.), Ae.polynesiensis Marks, Culex annulirostris Skuse and Cx quinquefasciatus Say. Treatments were completed within a week, in January 1990. Fish quickly eliminated mosquito larvae from the open breeding sites (ponds, wells). The impact of copepods in water tanks, drums and covered wells was inconsistent, apparently depending on the availability of microfaunal diet for growth of copepod nauplii. As the biting rate of adult Ae.aegypti seemed to be unaffected by the biological control of larvae, this village-scale experiment was judged to be unsuccessful as a means of vector control.

Aedes↗
PubMed2001

Cross-resistance and inheritance of resistance to Bacillus thuringiensis toxin Cry1Ac in diamondback moth (Plutella xylostella L) from lowland Malaysia.

A field population of Plutella xylostella from Malaysia (SERD4) was divided into five sub-populations and four were selected (G2-G5) with the Bacillus thuringiensis insecticidal crystal (Cry) toxins Cry1Ac, Cry1Ab, Cry1Ca and Cry1Da. Bioassay at G6 gave resistance ratios of 88, 5, 2 and 3 for Cry1Ac, Cry1Ab, Cry1Ca and Cry1Da respectively compared with the unselected sub-population (UNSEL-SERD4). The Cry1Ac-selected population showed little cross-resistance to Cry1Ab, Cry1Ca and Cry1Da, (3-, 2- and 3-fold compared with UNSEL-SERD4), whereas the Cry1Ab-SEL sub-population showed marked cross-resistance to Cry1Ac (40-fold), much greater than Cry1Ab itself. In contrast, the Cry1Ca- and Cry1Da-SEL sub-population showed little if any cross-resistance to Cry1Ac and Cry1Ab. The mode of inheritance of resistance to Cry1Ac was examined in Cry1Ac-selected SERD4 by standard reciprocal crosses and back-crosses using a laboratory insecticide-susceptible population (ROTH). Logit regression analysis of F1 reciprocal crosses indicated that resistance to Cry1Ac was inherited as an incompletely dominant trait. At the highest dose of Cry1Ac tested, resistance was recessive, while at the lowest dose it was almost completely dominant. The F2 progeny from a back-cross of F1 progeny with ROTH were tested with a concentration of Cry1Ac that would kill 100% of ROTH. The mortality ranged between 50 and 95% in seven families of back-cross progeny, which indicated that more than one allele on separate loci were responsible for resistance to Cry1Ac.

Animals↗
PubMed2004

Prey stage preference and functional response of Euseius hibisci to Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae).

The aims of this study were: (a) determine the prey stage preference of female Euseius hibisci (Chant) (Phytoseiidae) at constant densities of different stages of Tetranychus urticae Koch (Tetranychidae), (b) assess the functional response of the predator females to the varying densities of eggs, larvae, or protonymphs of T. urticae, and (c) estimate the functional response of E. hibisci when pollen of Ligustrum ovalifolium was present as well. We conducted experiments on excised pieces of strawberry leaf arenas (Fragaria ananassa) under laboratory conditions of 25+/-2 degrees C, 60+/-5% RH and 12 h photophase. Our results indicated that the predator consumed significantly more prey eggs than other prey stages. Consumption of prey deutonymphs and adults was so low that they were excluded from the non-choice functional response experiments. The functional response on all food items was of type II. The two parameters of the functional response were estimated for each prey type by means of the adjusted non-linear regression model. The highest estimated value a' (instantaneous rate of discovery) and the lowest value of Th (handling time, including digestion) were found for the predator feeding on prey eggs, and a' was lowest and Th highest when fed protonymphs. Using the jack-knife method, the values for the functional response parameters were estimated. The values of a' and Th produced by the model were similar among all prey types except for the eggs, which were different. Using pollen simultaneously with prey larvae decreased the consumption of the latter over the full range of prey densities The suitability of this predator for biological control of T. urticae on strawberry is discussed.

Animals↗
PubMed2004

[Effects of ultra low volume Beauveria bassiana oil formulation on biological diversity].

In 2001-2003, an ultra low volume (ULV) Beauveria bassiana (Bb) oil formulation was used to prevent against Dendrolimus punctatus, and its effect on biological diversity (species richness, individual number, species diversity index and evenness index, and dominant index) was investigated. The results showed that there were 473, 392 and 266 species in non-control, Bb control and chemical control areas, respectively. The individual number ratio of natural enemies to pest in Bb control area (0.1049:1) was close to that in non-control area (0.1051:1), but much higher than that in chemical control area (0.0558:1). In Bb- and chemical control areas, the species richness and diversity decreased, but dominant index increased. There existed significant difference between chemical control and non-control areas, but no significant difference was found between Bb control and non-control areas. ULV Bb had no obvious effect on the natural enemies and non-target insects.

Biodiversity↗