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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 L earthen water-storage jars was studied by exposing the packets for four to nine wk in one set ofjars and then transferring them sequentially to new sets ofjars 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 1 g/100 L (0.05 mg/L 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/L AI) per 200-L 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 Ae. 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 program more cost effective.

Novaluron, a new chitin synthesis inhibitor type of insect growth regulator, was evaluated in the laboratory and field against larvae of the mosquito Aedes aegypti (L.). In the laboratory, the technical material showed a high level of activity against 2nd and 4th instar larvae. The inhibition of emergence (IE) was 100% at concentrations of 0.25 to 1.0 microg/L. Second instars were slightly more susceptible than fourth instars. At the high concentration (1 ppb), most of the mortality occurred in the larvae, but at sublethal concentrations (for larvae) mortality also occurred in pupae and adults (incomplete eclosion). An EC10 (emulsifiable concentrate containing 10% active ingredient) formulation of novaluron was evaluated against Ae. aegypti in water-storage containers in the field in Thailand. Two tests at high (0.05 to 1 mg/L) and low (1 to 20 microg/L) concentrations were carried out in clay jars (200 L) and plastic pails (75 L). At high concentrations in clayjars, we obtained 86-96% inhibition of emergence (IE) for about 190 d, but the mortality declined at low concentrations after 190 d. At much lower concentrations, in jars and plastic pails in the second experiment, the IE was 80-100% for 2 mo. The highest concentrations of this series (10 microg/L in jars and 20 microg/L in pails) were active for 75 and 68 d respectively, losing efficacy by 82 d post-treatment. In the experiment using low concentrations, all treatments in jars and plastic pails failed to provide adequate control 90 d after treatment. These studies show that novaluron, even as EC10, has exceptional long-term activity against Ae. aegypti in water-storage containers, with higher concentrations yielding greater long-term control than low concentrations.