Sequential release and residual activity of temephos applied as sand granules to water-storage jars for the control of Aedes aegypti larvae (Diptera: Culicidae)
Thavara, U.; Tawatsin, A.; Srithommarat, R.; Zaim, M.; Mulla, M.S.
Journal of Vector Ecology Journal of the Society for Vector Ecology 30(1): 62-72
2005
ISSN/ISBN: 1081-1710 PMID: 16007957 Document Number: 591798
Two long-term experiments were carried out on the release profile and efficacy of temephos 1% GR (sand granules) against Aedes aegypti larvae in water-storage containers. In the first experiment, the efficacy of temephos 1% GR enclosed and tied in a muslin cloth and placed in water at the bottom of 200 litre earthen water-storage jars was studied by exposing the packets for four to nine wk in one set of jars and then transferring them sequentially to new sets of jars four times successively. Temephos released slowly from the granules, the magnitude of release being adequate in the initial period of two to three wk after treatment. Following this period, the efficacy of the granules increased substantially where 92-100% inhibition of emergence even at the lowest dosage of 1g/100 litre (0.05 mg/litre AI) was obtained for about another five mo or longer. On removal of the packets from a given set of jars, the released residues remaining in the jars and water lasted a maximum of one to six wk post-removal depending on the magnitude of prior release into the jars. This experiment provided clear evidence that temephos is released slowly over a long period of time in water-storage jars. In the second experiment, we compared the efficacy of temephos 1% GR at 1 and 10 g (0.05 and 0.5 mg/litre AI) per 200-litre water in jars painted and unpainted on the inside. The efficacy in the painted jars, although high, was consistently lower than that in the unpainted jars, where 99-100% control of larvae was achieved at both rates for a minimum of five mo after treatment. On the basis of this experimental evidence, it is desirable to study the efficacy of lower dosages of temephos than those currently used in A. aegypti control programs. The use of controlled release formulations or sachets that are retrievable during cleaning and washing will be more practical and desirable. Both of these interventions will make the programme more cost effective.