Abstract:
The present study evaluated the efficacy of nine larvicides for bio-rational
management of mosquito larvae in Bangladesh from 30 September 2018 to 11
February 2019. Experiment was conducted in the laboratory of SAU and insecticides
used in this experiment are spinosad, emamectin-benzoate, pyrazine, buprofezin,
cyfluthrin, lambda-cyhalothrin, temephos, neem seed kernel extract, neem leaf extract
at different concentration. Dosages used in this experiment were; spinosad (dose:1
ppm, 2 ppm, 5 ppm and 10 pmm), cyfluthrin (dose: 1 ppm, 2 ppm, 5 ppm and 10
pmm), lambda-cyhalothrin (dose:1 ppm, 2 ppm, 5 ppm and 10 pmm), pyrazine (dose:
25 ppm, 40 ppm, 80 ppm, 160 ppm), emamectin-benzoate (dose: 25 ppm, 40 ppm, 80
ppm, 160 ppm), buprofezin (5 ppm, 10 ppm, 20 ppm, 40 ppm) temephos (10 ppm, 5
ppm, 2 ppm, 1 ppm) and two botanical as neem leaf extract(dosages: 30000 ppm,
50000 ppm, 100000 ppm, 200000 ppm) and neem seed kernel extract(dose:1.0 ppm,
2.0 ppm, 5 ppm,10 ppm). Of the nine larvicides tested lambda-cyhalothrin gave the
lowest median lethal concentration of LC
0.000848 thereafter temephos gave
second lowest median lethal concentration of LC
50
0.00114 after 48 hours and
spinosad gave third lowest median lethal concentration of LC
50
0.00433. It was
followed by cyfluthrin with LC
50
1.1067, buprofezin with LC
50
50
1.7650, neem seed
kernel with LC
50
2.3360, pyrazine with LC
50
6.0700, emamectin-benzoate with LC
7.5823 and neem leaf extract gave median lethal concentration of LC
10534. From
the study it was revealed that order of toxicity of nine larvicides is lambda-cyhalothrin
> temephos > spinosad > cyfluthrin > buprofezin > neem seed kernel extract >
pyrazine > emamectin -benzoate > neem leaf extract. Mortality percentage also
calculated to find out the efficacy of nine larvicides. Lambda-cyhalothrin and
temephos gave highest mortality percentage of 100% after 48 hour. From the study
we found the order of mortality percentage of nine larvicides is lambda-cyhalothrin >
temephos > spinosad > pyrazine > emamectin-benzoate > buprofezin > neem seed
kernel extract > neem leaf extract > cyfluthrin. Considering environmental safety
temephos and spinosad could be effectively used for mosquito larvae control in
stagnant water bodies and lambda-cyhalothrin in small containers retaining water
temporarily with appropriate dosages.