1. Medical Research Institute
Department Of Entomology
23.05.11
Registrar of Pesticides
Office of the Registrar of Pesticides
Department of Agriculture
Getambe
Peradeniya
Report on the biological efficacy of Mosquito larvicide Sample No. WP/10/21 and RH/0/22
(Bacillus thuringiensis)
The biological efficacy of Mosquito larvicides, sample numbers WP/10/21 and RH/0/22
(Bacillus thuringiensis ) were tested against the laboratory reared 4* instar larvae of Aedes
aegypti. The larval bio assays were carried out according to the WHO guidelines for the
laboratory testing of mosquito larvicides. Laboratory reared 25, 4* instar larvae were exposed to
4 replicates as well as for the controls. The mortality was counted after 24 hr exposure period.
Observation -100% mortality of the larvae of Aedes aegypti were observed in all the replicates
used. The residual activity of the products were observed upto 30 days under laboratory
conditions and 100% mortality of the mosquito larvea were observed during that period.
The biological efficacy of the Mosquito larvicides, sample numbers WP/10/21 and RH/0/22 were
tested under field conditions, according to the WHO guidelines for the testing of mosquito
larvicides. In these trials, artificial containers (barrels.) of water were placed in the field and
mosquito larvicides were tested against field-collected larvae. The water-filled containers were
given a period of 24 h for conditioning. A batch of 50 field collected , third instar larvae of Aedes
aegypti, were released into each container and larval food was added. Four replicates were
carried out with a control. The containers were treated with mosquito larvcides and covered
with nylon mesh screen to prevent other mosquitoes or other insects from laying eggs. All the
containers were examined afte 24 hrs. and live larvae were counted to score post-treatment
larval mortality. To test residual activity, a new batch of field collected / laboratory-reared, late
third / early 4'*' instar larvae of the same mosquito species were introduced to each container, and
mosquito larval food was added on alternate days or weekly.
Larvae survival was assessed 24 h post addition. This process continued upto 30 days.
Observation - 100% mortality of Aedes aegypti was observed after 24 hrs. of the application
of the product. The residual effect of the mosquito larvicides sample numbers WP/10/21 and
RH/0/22 were was observed for 30 days and observed 100%) mortality of Aedes aegypti during
that period
Thanking you.
Yours sincerely
Dr. l.S.Weerasinghe
Entcmol'-yist ^R D A N I S T E R
D DE SILVA MAWATHA COLOMBO 8 SRI LANKA
Dop-^itrnent o f Er,?.oviio?ogy P H O N E : 9 4 - 1 1 - 2 6 9 1 3 50 FAX: 9 4 - 1 1 - 2 6 9 1 4 50
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