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PubMed2006

Field evaluation of Bacillus thuringiensis H-14 against Aedes mosquitoes.

Studies were carried out on the residual efficacy of Bacillus thuringiensis H-14 (water dispersible granule, VectoBac ABG 6511) as direct application in the control of Aedes larvae in the field. Field Aedes sp populations in the earthen and glass jars were predetermined before initiation of the trial. On confirmation of the presence of Aedes species in the designated area, Sungai Nibong Kecil, Penang Island, Malaysia, Bti was introduced in the 55L earthen and 3L glass jars). Two test designs were carried out. The first design had treated water replenished daily with 6L of seasoned water and the second design is without the replenishment of water but evaporated water was replenished. Bti was effective in the field for at least 35 days with more than 80% reduction in the Aedes larvae in the treated containers. For earthen jars with daily replenishment of water, 100% reduction was recorded for the first 3 days, while more than 80% reduction was recorded up to day 40. At day 60, Bti still provided an efficacy of 54.32 +/- 4.61 (%) of reduction. Whilst for earthen jars without daily replenishment of water, 100% reduction was recorded for the first 5 days, while more than 80% of reduction was recorded up to day 40. For the glass jars studied, similar efficacy was observed. In jars with daily replenishment of water a better larval control was observed. Percentage of reduction from day 50 to 60 for replenishment of water was between 50 to 70% compared to without replenishment of water with less than 40%.

Aedes↗
PubMed2006

Formulation of tablets from the crude extract of Rhinacanthus nasutus (Thai local plant) against Aedes aegypti and Culex quinquefasciatus larvae: a preliminary study.

Dried root powder of Rhinacanthus nasutus, Thong Phan Chang (Thai name) were extracted with methanol (MeOH) in a Soxhlet apparatus and made into 2 formulations of tablet containing the extract at 5% and 10% concentration. Due to the viscous and poor flow properties of the crude MeOH extract obtained, a wet granulation method was conducted in developing the tablets. Lactose was used as a filler. Polyvinyl pyrrolidone (PVP) K30 (15% w/w solution in alcohol) was used as the binding agent, while stearic acid (2% w/w) was used as a lubricant. Both formulas of prepared tablets had a smooth shiny surface with a round shape. Other physical properties of the tablets, such as weight variation, friability and disintegration time, met the requirements of the USP XX standard. The mosquito larvicidal activity of prepared tablets containing 5% and 10% R. nasutus extract against Aedes aegypti were not significantly different from each other (p > 0.05), with 48-hour LC50 values of 13.6 and 14.2 mg/I for the 5% and 10% tablets, respectively, while their activities against Culex quinquefasciatus were similar (p > 0.05) with LC50 values of 18.7 and 17.3, respectively. The larvicidal activity levels against Ae. aegypti and Cx. quinquefasciatus were also not significantly different from each other (p > 0.05). No larval mortality was observed in the two control groups: lactose solution and dechlorinated water. Toxicity to female and male fish (Poecilia reticulata) was tested with the prepared tablets. The toxicity of tablets containing 5% and 10% extracts were not significantly different from each other for the P. reticulata females with 48-hour LC50 values of 105.2 and 110.8 mg/I, respectively, and for P. reticulata males with LC50 values of 99.1 and 103.4 mg/I, respectively. Female and male P. reticulata were sensitive to the same dose of the extract. No fish died in the two control groups, with lactose solution and dechlorinated water. Acute-toxicity bioassay with fish showed that with an exposure of 48 hours the LC50 values of the tablets containing 5% and 10% were 5- to 10-fold higher than the LC50 of R. nasutus against mosquito larvae. These prepared tablets could possibly used to control mosquito vectors and be introduced into the mosquito control program.

Acanthaceae↗
PubMed1992

The SCS/ARS/CES pesticide properties database for environmental decision-making.

The only thing all pesticides have in common is that they are used to control pests. Otherwise, they come from almost every imaginable class of chemical. Everyone associated with pesticide use--farmers, Extension, EPA, state regulatory agencies, manufacturers, and environmentalists--needs information that will allow them to distinguish between pesticides that may be a problem as pollutants in certain situations, and those which may not. There are five basic properties that, when combined with information about site and use, provide much information about the potential of a pesticide to be a pollutant. These five properties are solubility in water, volatility, soil sorption tendency, persistence, and ionization potential. We have compiled the most complete collection of these properties available, using others' compilations but verifying values from the primary literature in many cases. A complete primary literature search was not done. For each parameter we suggest a "Selected Value" which we believe to be the best available, recognizing, however, that persistence and soil sorption are sensitive to specific site conditions. These Selected Values are being incorporated into pesticide environmental-impact risk assessment procedures by state and federal agencies, and are considered to be consensus values. However, there is a serious potential for misuse of these data, particularly the error of using small differences between active ingredients to make regulatory distinctions between them. The ability to relate these data to environmental impact is an essential need and is improving, but is currently at a primitive level.

Animals↗
PubMed1991

[Experimental models for study of fluorosis].

In most animal species, acute fluorosis is triggered by the accidental consumption of substances with a high content of fluorine, widely used in pest control. Fluorine normally concentrates in bones and teeth, and forms nearly 0.05% of these structures in mature animals, positively contributing to increase resistance of enamel to caries and favoring mineralization after eruption, a process which increases with age. The present article submits a form of study of fluorosis, stressing due warning as to its harmful effects.

Animals↗
PubMed1991

Exposure to inorganic bromides from greenhouse crops where methyl bromide was applied for soil fumigation.

The Authors determined the concentration of inorganic bromides in soil and tomatoes from greenhouses where soil fumigation had been performed using methyl bromide (greenhouse B) and alternative pest control systems (greenhouse A and greenhouse B) before planting. The results obtained demonstrate that concentration of inorganic bromides in foodstuffs should be considered as a marker of exposure to methyl bromide poisoning risk.

Bromides↗
PubMed1991

Fermentation of a Malaysian Bacillus thuringiensis serotype H-14 isolate, a mosquito microbial control agent utilizing local wastes.

A screening program searching for indigenous microbial control agents of mosquitos in Malaysia is initiated since 1987 and to date at least 20 isolates of mosquitocidal Bacillus thuringiensis serotypes have been obtained. Preliminary field evaluation of several isolates indicated that they are highly effective in the control of medically important mosquito species. For operational purposes, there is an urgent need to produce this agent utilizing cheap and locally available wastes through fermentation biotechnology. Fermentation studies in shake-flasks containing standard nutrient broth and soya bean waste, respectively, indicate that it takes about 37 hours for a Malaysian isolate of B. thuringiensis serotype H-14 to mature. In the grated coconut waste, fishmeal and rice bran, the bacteria took 28 hours, 26 hours and 126 hours respectively to mature. The endotoxin was harvested from the standard nutrient broth at 55 hours and at 50 hours from soybean, grated coconut waste and fishmeal. The endotoxin could only be harvested 150 hours after inoculation from rice bran medium. However, no bacterial growth was detected in palm oil effluent. In terms of endotoxin and biomass production, fishmeal appears to be a suitable medium. Variations in the pH of the fermenting media were also noted.

Agriculture↗
PubMed1990

[The pathogens of Taiwan mosquitoes--Coelomomyces species].

A brief mention was made of the history of world studies on the Coelomomyces fungi, the life cycle of the fungi, their importance as biological agents for mosquito control, and the known ecological information concerning the Taiwan mosquitoes parasitized by the fungi. Special accounts were made of the results of experiments infecting four mosquito species, Aedes aegypti, Ae. albopictus, Ae. triseriatus and Tripteroides aranoides with Coelomomyces stegomyiae var. chapmani, using the copepod, Phyllognathopus viguieri as an alternate host. The dead 4th instar larvae of Ae. albopictus containing sporangia were put together with healthy copepods for 10 days, then healthy 2nd instar mosquito larvae were added for a 1-day exposure. Then the larvae were transferred to clean water and subsequent examinations for signs of infection were made at 3-day intervals for a period of 21 days. The experiments demonstrated an infection rate of 59.7% and 90% respectively for Ae. albopictus and Ae. aegypti in the first trial, 18.5% and 23.3% in the 2nd trial, and none in the 3rd trial. The low infection rate in the 2nd trial and no infection in the 3rd trial were thought to be due to the extensive contamination of test water with algae. Therefore, in the 4th trial the rearing water was renewed with dechlorinated tap water and new copepods instroduced. The infection rate again rose to 41.1% and 56% respectively for the two species. Experiments with Ae. triseriatus and Tp. aranoides failed to produce signs of infection. Experimental infection of susceptible Ae. albopictus larvae with the sporangia stored at 8 degrees C showed that storage for one month produced an infection rate of 38.2%. However, storage for two months or longer produced no infection in the larvae of the same mosquito species.

Aedes↗
PubMed1990

The effect of Bacillus thuringiensis israelensis [H-14] on emergence of Mansonia mosquitos from natural breeding habitat.

The measurement of the ultimate effects of the microbial insecticides on mosquito density is best obtained by assessment of adult populations. The main aims of this study are: (1) to assess the effect of Bacillus thuringiensis israelensis (Bti) FC Skeetal and Bactimos briquettes on the emergence rate of Mansonia bonneae developed from the introduced first-instar stage larvae and (2) to measure the effect of these two formulations of insecticides on Mansonia adult populations emerging from the natural breeding plots. Bti Skeetal and Bactimos briquettes at the lower applied dosages of 2.3 kg/ha and 1 briquette case/20 m2 respectively achieved 39-40% pupation rates and 31.5-34.2% adult emergence rates. At these low applied dosages, there was little or no direct effect on pupation from the surviving larvae and thereafter on the emergence of adults from the pupae. A two-fold increase in dosage, however, produced a drastic decline in the pupation rate and adult emergence rate. The rates dropped to 6.5% (pupation) and 4.3% (adult emergence) of the total larvae for Bactimos briquettes and to merely 1.5% (pupation) and 1.3% (adult emergence) of the total larvae for Skeetal. In studying the effect of Bti on the field populations of Mansonia mosquitos, two plots each were treated with Bactimos at 1 briquette case/10 m2 and Skeetal at 4.6 kg/ha. A wooden pyramid-shaped screened cage was placed on a cluster of host plants for a period of 2 weeks to trap the emerging adult mosquitoes. There were a total of 24 clusters of host plants in each plot.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Isolation of indigenous larvicidal microbial control agents of mosquitos: the Malaysian experience.

A nationwide screening program searching for microbial control agents of mosquitos was initiated in Malaysia in 1986. A total of 725 samples were collected and 2,394 bacterial colonies were isolated and screened for larvicidal activity. From such screening, 20 Bacillus thuringiensis, 6 B. sphaericus, 1 Clostridium bifermentans and 2 Pseudomonas pseudomallei larvicidal isolates were obtained. Of these, a new B. thuringiensis named as subspecies malaysianensis was found, while the C. bifermentans was also a new anaerobe individualized as serovar malaysia. It was concluded that this screening program was highly successful.

Animals↗
PubMed1990

[Distribution pattern of chemicals in surface waters as a reflexion of entry pattern--description of the problems].

The distribution pattern of persistent substances made transparent chemically-analytically, in surface waters reflects--considering spatial-temporal limitations--an image of the input pattern. This permits in special cases repercussions on attributable (industrial enterprises, trade, plant production, pest control) or partly or completely anonymous (landfills, ancient deposits, contamination centres, traffic, atmospheric depositions) causative agents The classification of these information requires the knowledge of substance and substrate specifics, especially detailed information about production and/or application of the substances and so represents an interdisciplinary task. Assessing single substance analyses permits a comparison with limit values or literature data. The consideration of combinations of substances which belong together due to production, application and/or transformation may help to elucidate the input patterns. This differential-diagnostic method is presented by a first evaluation of analytical findings in surface waters of an industrialized town and its surroundings.

Hydrocarbons, Halogenated↗
PubMed1990

[Application and environmental impact of the biocontrol agent--Bacillus thuringiensis subsp. israelensis for vector control].

In 1976, Goldberg and Margalit found a potent isolate of Bacillus thuringiensis subsp. israelensis, which has great mosquitocidal activity and was commercialized within 5 years in the USA. It is now the only bio-control agent on the market for vector control worldwide. Because of concerns about environmental pollution and ecological preservation, vector control can no longer be solely dependent on the use of chemicals. It appears that the best strategy is to be integrated with biological control. When considering the value and future progress of BTI, it is important to evaluate applicability based on (1) production technology and economic considerations (2) standardization and quality control, and (3) field realization and environmental impacts. Finally, government policy and regulation limitations are the key factors which influence the availability of BTI in the vector control program.

Animals↗
PubMed1990

[The biocontrol of container-breeding mosquitoes by using Toxorhynchites].

Container-breeding mosquitoes not only bite people but also transmit many human and animal diseases. The problem with chemical control of these mosquitoes is that the breeding sites are always well dispersed and not easily located, and more manenergy and money are required to treat them individually. Since the adverse effects of pesticides on vector control have been recognized, Toxorhynchites mosquitoes are being reconsidered as a means of reducing the populations of other mosquito species. The bionomic interaction of predator and prey, mass rearing, and some examples of biological control of Toxorhynchites are discussed in this article. Integrated controls combining periodic mass release of gravid Toxorhynchites females and ULV pesticide applications can be used to suppress container-breeding mosquitoes.

Animals↗
PubMed1990

[Applications of bacterial pathogens to the mosquito control].

Both Bacillus thuringiensis subsp. isrealensis (Bti) and Bacillus sphaericus are common bacteria found in a variety of soil and aquatic habitats. Some strains of them can produce a protein crystal, called parasporal body (or crystal) beside the spore in the cell during sporulation, and it is toxic if eaten by mosquito larvae. As the parasporal bodies are ingested into a mosquito digestive tract, they will be digested and activated by certain enzymes in alkaline digestive juice. The activated toxins can destroy midgut epithelium and other tissues, and then the mosquitoes will be intoxicated and killed. There are some factors affecting efficiency of the toxins produced by these two mosquitocidal bacteria. First, the toxicity of the toxins will decrease as larval age and density increase. Second, difference in mosquito species will demonstrate a different tolerance to both toxins. However, larvae of Anopheles are more tolerant to Bti than those of Aedes and Culex; whereas larvae of Aedes are more tolerant to B. sphaericus than Culex and Anopheles. Environmental factors are as important as the mosquito hosts in influencing the efficiency of the toxins. For examples, raising temperature under suitable ranges may increase the toxicity of the toxins. The UV light of sunlight could inhibit activity of the toxins and therefore decrease their efficiency. Quality and depth of the water are also important environmental factors affecting toxicity of the toxins to the mosquito larvae. The precipitation of the crystal and organic materials absorbing the toxins decreases their toxicity to the mosquito larvae as well.

Animals↗
PubMed1990

[Preliminary study on the biological control of dengue vectors by fish in Liouchyou Prefecture, Pingtung County, Taiwan].

An investigation made in May 1989 with questionnaires to 2,480 families in Liouchyou Prefecture, Pingtung County, showed that there were about 6,533 water containers in the whole village, of which 49.83% were used to store water for drinking, and the remaining 50.17% were used for washing clothes and watering plants. 32.42% of the residents volunteered to rear fish in the family water containers to control the mosquito population. During the period from April to October 1989, there was a total approximately 17,600 Gambusia affinis, Poecilia reticulata, Tilapia mossambica, and Sarotherodon niloticus released into the household water containers in the Liouchyou areas to control dengue vectors--Aedes aegypti and Aedes albopictus. One month after the release, a comparison of the container index of Aedes larvae showed that among 530 containers with fish in them, the positive container index was 3.58; among the 3,219 containers without fish in them, it was 25.97. Furthermore, the positive container index without fish was as high as 97.32 in May 1989, and dropped to as low as 18.00 at the end of September 1989. This indicats that rearing fish to control household mosquitoes yielded significant results in the initial stage. Also, in some water containers Gambusia affinis and Porcilia reticulata lived longer than five months, and Gambusia affinis could eat 31.33 Aedes larvae/0.4078g fish per day on the average. It appears that the biological control of dengue vectors by fish in the Liouchyou areas would be advantageous.

Animals↗
PubMed1987

Microcarriers as a culturing system of insect cells and insect viruses.

There is an increasing interest in culturing of insect cells, which are host for arthropod-born (Arbo) viruses. The potential applications of Arbo viruses are in the following two main fields: 1. Medical applications (e.g. preparation of viral vaccines and viral antigens for diagnostic purposes). 2. As bioinsecticides in pest control in horticulture, agriculture and forestry. One of the potential cell substrates for these applications is an anchorage-dependent-mosquito cell line established from embryonic tissues of Aedes aegypti (AA). The following areas were investigated in the reported research with the AA cell line: The AA cells were successfully propagated in microcarrier (MC)-culturing-systems. Of the tested MC's the cellulose-based microgranular MC (DE-53 of Whatman, having an exchange capacity of 2 meq/g) was found to be the best MC. Cells grew in MCs-cells aggregates in submerged spinner culture. The AA-MC's culture was successfully scaled-up to 8 litre culture volume. "Trypsinization" of the AA cells from the MC surface is successfully done by RDB, a dispersion agent from a plant origin (produced and marketed at the author's Institute). Other known dispersion agents (trypsin, collagenase, pronase) failed to disperse the AA cells from the MC. A serum-free medium was developed for culturing the AA cells on the DE-53 MC's. Bovine serum albumin was the main serum substituant in the developed medium. Arboviruses, from the Toga group, were grown in the AA-MC culture. Sindbis virus (from alpha-group) and West Nile virus (from the Flavi group), chronically infected the AA cells, which continuously produce and liberate these two viruses.(ABSTRACT TRUNCATED AT 250 WORDS)

Aedes↗
PubMed1985

Evaluation of slow-release formulations of temephos (Abate) and Bacillus thuringiensis var. israelensis for the control of Aedes aegypti in Puerto Rico.

Formulations of temephos (Abate) and Bacillus thuringiensis var. israelensis (B.t.i.) on corncob and dried coconut husk carriers were tested for slow-release insecticide properties against Aedes aegypti larvae in Puerto Rico. Granular formulations of 5% and 10% temephos gave continuous larval control in used automobile tires for 27 to 124 days and 34 to 162 days, respectively. Temephos on radial sections of corncob and coconut husk chips gave good larval control in tires for 27 to 63 and 61 to 134 days, respectively, depending on the size of the carrier. Small (2-3 g) and large (3-5 g) coconut husk chips tested in 167 liter drums provided continuous control for 55 to 105 days, respectively. Granular formulations of B.t.i. controlled Ae. aegypti in tires for 19 to 33 days, and B.t.i. briquets exhibited larvicidal activity in large containers for 26 to 78 days.

Aedes↗
PubMedDate not supplied

[Recent experience with mites in stored products].

The A.A. refer a recent experience about the isolation and identification of same species of storaged timber mites. They believe that these mites are responsible of dermatitis at the trunk and the arms of timber workers. Mites are the most elderly living species on the earth, they can live and grow in different environments, such as plants, flowers, animals, men, earth, lake and sea waters, organical rubles, houses, mattresses, old books etc. There are free-living, saprophitic, parasitic and predator mites. Generally, primary mites live either freely or as commensals feeding on conserved foodstuff and on what they find available. Secondary mites, i.e. parasites and predators, live off primary mites and insects infesting foodstuff. Direct damage to foodstuff are not to be considered important, whereas indirect damages are more serious, due to the contamination of bodies and stools of mites that are rich in nitrogen. Some secondary mites may attack foodstuff workers causing characteristic dermatitis: they can act either directly, by sting and bites, or indirectly, provoking on allergic hypersensitivity. In this study the A.A. used the floating method to isolate timber mites, and then, these have been photographed at the microscope to obtain an easier and more complete identification. The A.A. describe a heterogeneous fauna consisting of both adult and larval-status insects, some species of free-living mites (Oribatula Tibialis) and, in particular, of two species secondary mites, predator, belonging to the Prostigmata sub-order. The Cheyletus Eruditus (Cheylatidae family) is a whitish mite feeding mostly on insect larva and primary mites living in foodstuff. When no prey is available, the Cheyletus Eruditus eats individuals of its own species. The Pyemotes Herfsi (Pyemotidae family) is a little white mite feeding on insect larva. It lives in conserved foodstuff and may attack man causing characteristic dermatitis such as those described by the A.A. The A.A. conclude dealing with the possible preventive and therapeutic measures tend to keep phisic-chemicals parameters of foodstuff and others conserved products afar from the values suitable for the growth of parasites (water content min. 13%, environmental humidity min. 60-65%, appropriate temperature etc.). Therapeutic procedure are based either on physical media: infra-red rays, gamma-rays, electric fields for the transformation of temperature or using chemical mixtures containing methyl bromide, carbon tetrachloride and hydrogen sulphide. Among the therapeutic procedures, however, the biological pest control using chemical media associated with antagonist mites of the infesting species is to be preferred.

Animals↗