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PubMedDate not supplied

Control of mosquito larvae by encapsulated pathogen Bacillus thuringiensis var. israelensis.

Bacillus thuringiensis var. israelensis (B.t.i.) containing alginate microcapsules were prepared in order to maintain durable formulations which could resist several effects causing reduced efficiency during applications. B.t.i. spores were harvested through NYSM agar plates and encapsulated in Ca-alginate (0.5-2.0% w/v) gels without any significant loss of sporal or larvicidal activity. The effect of acidic pH on the larvicidal toxin was tested using Culex sp. larvae in the laboratory. The alginate microcapsules pretreated with saturated KH2PO4 solution gave larvicidal activity after 24-48 h, by bioassay. Suspension and encapsulated forms of the pathogenic bacterium were exposed to pH variations (3.0-10.0), UV light and high temperature (50 degrees C). Durability to Pb++, Cu++, Fe++ compounds and phenol was also examined. As the alginate content increased, stability of B.t.i. drastically increased against the tested effects, but to obtain useful releasing microcapsules, 1.0-1.5% w/v alginate concentrations were found to be optimum.

Alginates↗
PubMed1998

Bacterial control of mosquito larvae: investigation of stability of Bacillus thuringiensis var. israelensis and Bacillus sphaericus standard powders.

Bacillus thuringiensis var. israelensis and Bacillus sphaericus products were assayed against their respective reference powders IPS82 and SPH88. Since their production in 1982 and 1988, the potency and larvicidal activity of these standard powders have been regularly checked on their test insects Aedes aegypti (for IPS82) or Culex pipiens (for SPH88). Over the 16-year evaluation period of IPS82 and 10-year evaluation period of SPH88, their potencies were considered stable. The global mean of each year's mean showed a coefficient of variation of less than 20%. Larval rearing was the most important factor in the reproducibility of the bioassay, although some variation also originated from the person performing the bioassay. This study demonstrated that the SPH88 standard could be kept in a stock suspension at 4 degrees C for 3 years without loss of potency. Moreover, after 9 years of storage in suspension, only a 2-fold decrease in the potency of SPH88 was detected.

Aedes↗
PubMed1990

Evaluation of the control of mosquitoes with insect growth regulators.

In this study, the effectiveness of eight insect growth regulators (IGRs) (chlorfluazuron, diflubenzuron, EL-494, flufenoxuron, teflubenzuron, juglone, plumbagin and methoprene) against five mosquito vectors (Armigeres subalbatus, Aedes albopictus, Aedes aegypti, Culex tritaeniorhynchus, and Culex quinquefasciatus) was investigated in the laboratory. The EC50s of chlorfluazuron, diflubenzuron, EL-494, flufenoxuron, teflubenzuron, and methoprene against the five mosquitoes ranged from 0.0001 to 0.3 ppm and those of juglone and plumbagin from 3-25 ppm. The five mosquito species had similar tolerances to the test IGRs. At pH 5 to 9, the effectiveness of the first five chemicals was very stable. After ultraviolet irradiation or heat management (45 degrees C-60 degrees C), diflubenzuron and flufenoxuron were very stable. EL-494 was not stable when exposed to ultraviolet irradiation or heat. Under 0.1 ppm, teflubenzuron was not stable upon exposure to heat and chlorfluazuron and methoprene were not stable when exposed to ultraviolet irradiation. Piperonyl butoxide reduces the effectiveness of the five IGRs. Administration of diflubenzuron (1-5 ppm), flufenoxuron (0.025 ppm), and teflubenzuron (1-5 ppm) reduced Culex quinquefasciatus larvae in ditches by 40-90%. The administration of diflubenzuron (0.5 ppm) to containers reduced 97% of the Aedes albopictus larvae.

Animals↗
PubMed1987

Control of mosquito nuisance in Britain.

The situation regarding mosquito nuisance and control in Britain is presented together with data resulting from a questionnaire circulated to Local Authorities throughout England, Scotland, Wales and Northern Ireland. Details of several recent control programs are given.

Animals↗