Acaricidal effects of fenvalerate and cypermethrin against Rhipicephalus (Boophilus) annulatus

The acaricidal effects of two most commonly used acaricides viz., fenvalerate and cypermethrin against Rhipicephalus (Boophilus) annulatus were studied using Adult Immersion Test (AIT). The LC50 values observed for fenvalerate and cypermethrin were 1570 ppm and 184 ppm respectively. The death of ticks was not an immediate process. Fenvalerate caused death only after 7 days while cypermethrin after 5 days of treatment. The eggs laid by treated ticks did not hatch at all concentrations tested.

Acaricidal effect of Cassia fistula Linn. leaf ethanolic extract against Rhipicephlaus (Boophilus) annulatus

The present study evaluates the acaricidal properties of crude ethanolic extract of Cassia fistula leaves for controlling Rhipicephalus (Boophilus) annulatus based on adult immersion test (AIT). The percentage of adult mortality, inhibition of fecundity and hatching of ova laid were studied at different concentrations of the extract ranging from 50 to 100 mg / ml. The results were compared using one-way ANOVA. The extract produced complete inhibition of hatching of eggs at concentrations above 80 mg / ml of the extract. Mortality of adult engorged female ticks and inhibition of fecundity were concentration dependent. The LC50 value of extract against R. (B.) annulatus was 97.1 mg / ml.

In vitro evaluation of acaricidal activity of fipronil against Haemaphysalis bispinosa based on adult immersion test

Fipronil is a phenylpyrazole family insecticide which mainly affects the nervous system of insects. In the present study, the in vitro acaricidal effects of the compound against the widely prevalent multihost tick, Haemaphysalis bispinosa was assessed. The lowest concentration at which complete adult tick mortality was observed was at 25 ppm while complete absence of egg mass observed at 10 ppm. Hundred per cent inhibition of fecundity was observed at 1 ppm while complete blocking of hatching of the laid ova was observed even at 500 ppb.

Effects of solvents and surfactants against Haemaphysalis bispinosa

As per the report published by FAO (2004), the tick population in India has developed resistance against all the available acaricides. Hence, newer methods of control including potential herbal agents are required to reduce the problems caused by the ticks. Most of the herbal extracts or their fractions are dissolved in polar or non-polar solvents or detergents before tested for acaricidal activity and these diluents should be of little acaricidal activity. In the present study, adult immersion test (AIT) was carried out on adult engorged female Haemaphysalis bispinosa ticks to detect the acaricidal activity of different solvents viz., nbutanol, glycerol, acetone, ethanol, methanol and surfactants (at 1 per cent dilution) like dimethyl sulphoxide (DMSO), tween 20 and triton X- 100. The study revealed that methanol was the least toxic solvent while tween 20 (1 per cent) was the least toxic detergent against H. bispinosa.