In Argentina, more than 25,000 cases of dengue were reported in the summer of 2009, even in provinces where the disease was formerly absent. We analysed the susceptibility levels to the larvicide temephos in seven populations of Aedes aegypti, the primary vector of dengue, collected during summer 2007/2008, using the susceptible Rockefeller strain as a control. Although no control failures were observed during the experiment, a majority of the lethal concentration and resistance ratio values indicate an incipient resistance. An integrative program to monitor the resistance of Ae. aegypti to insecticides is needed in the country.

Ultra low volume (ULV) aerial spraying is a common methodology for spatial treatments for Aedes aegypti (L.) control. Previous studies from our laboratory indicated that the cis isomer of permethrin has an excellent efficacy for vector control, in particular for Triatoma infestans. It was of interest to determine the efficacy of this pure isomer in a ULV water-based formulation for adult A. aegypti control, since both vectors usually are found together in South America. A method is presented to make a quick measure at laboratory level of the knock down effect (KT50) of a new EC water-based formulation of cis-permethrin, in a small Peet Grady chamber of 0.34 m3, with a specially designed glass sprayer. A deltamethrin standard ULV formulation "CISLIN" was used for comparison. cis-Permethrin showed a significantly lower KT50 value than deltamethrin (7.50 and 9.65 min, respectively). When the mosquitoes were introduced into the chamber 10 min after spraying KT50 values were almost equal (15.59 and 15.88 min, respectively). In scaled up bioassays the ULV formulation of cis-permethrin showed 100% mortality of A. aegypti adult mosquitoes at the beginning of the treatment (t=0) and some mortality at 1h post treatment of freshly introduced mosquitoes. It was concluded that cis-permethrin could be an excellent tool for control of A. aegypti and other vectors of medical importance, with fewer side effects and better cost-effectiveness than with the cyanopyrethroids.

Isomers of pyrethroids usually have different insecticidal activities. Permethrin, a non-cyano pyrethroid, is not an exception and cis-permethrin is much more active than the trans-isomer against Triatoma infestans, vector of Chagas' Disease in Argentina. The large-scale separation of cis-and trans-permethrin was performed by successive recrystallizations from ethanol-water mixtures. An aqueous suspension concentrate (flowable) formulation of pure crystalline cis-permethrin was prepared and assayed for its insecticidal activity on wood and ceramic surfaces against nymph V of T infestans. This formulation was at least three times more effective than deltamethrin, with LC50 values on ceramic of 0.11 mu gcm(-2) and 0.33 mu gcm(-2) respectively. On wood surfaces, the LC50 value was 0.57 mug cm(-2) compared with 3.20 mu gcm(-2) for deltamethrin. Against other insect species such as Periplaneta americana, Aedes aegypti and Culex quinquefasciatus, the suspension concentrate formulation of cis-permethrin was, however, less effective than similar formulations of deltamethrin or beta -cypermethrin. (C) 2000 Society of Chemical Industry.

Topical application of different sulfhydryl (SH) reagents in acetone solution resulted in a deterrence of the feeding activity of Triatoma infestans nymph V. The ED50 for topical application of N-ethylmaleimide (NEM), the more active compound assayed, was 8.9 μg/insect. This effect showed a dose-dependent reversibility. We also observed feeding deterrency when a gauze cloth impregnated with NEM was located between the food source and the nymphs. After topical NEM treatment, mating deterrency was assessed by counting spermatophores dropped and eggs laid. When a population of adult insects, nymphal stages and eggs was reared in a cage containing filter papers treated with 0.4 mg/cm2 of NEM, a significant decrease of population density was seen after 200 days of exposure. Weekly replacement of filter papers impregnated with 0.13 mg/cm2 NEM for a period of one year enabled population control to be maintained. Antifeeding and antimating effects of NEM in Triatoma infestans and the resulting population control could be attributed to a chemoreceptor blockage produced by SH reagents.

1. A new series of organophosphorus compounds derived from N-substituted maleamic esters by reaction with dimethyl and diethyl phosphorodithioic acid was synthesized. 2. Two isomers, with chemical structures analogous to malathion were obtained for each maleamic ester assayed. 3. They were characterized, and their toxicity against a resistant strain of Musca domestica (strain G), a susceptible one (strain RAC) and Triatoma infestans (vector of Chagas' disease) were measured. 4. The structural chemical modification introduced by replacing a carboxyester group for a N-substituted amido one, reverted the resistance obtained for malathion. 5. Replacement of methyl by ethyl dithiophosphoric acid did not introduce significative differences. 6. In the case of Triatoma infestans, the synthesized compounds were less active than malathion.

1. Fenoxycarb (RO-13-5223) exhibits a strong juvenile hormone type of activity against Triatoma infestons.

The entomopathogenous agent Bacillus thuringensis var. israelensis (Bti or Bti H-14), produces a proteic toxin that is a promissory tool to use in chemical control of larvae of Aedes aegypti. Bti (H-14) as a liquid suspension, has been used in national campaigns against Ae. aegypti , vector of Dengue disease, but its lack of residual effect is a major inconvenient. In the search of new strategies in vector control, this paper presents some results of an alternative slow release formulation of Bti (H-14), the "Mosquito Dunks" . III instar or young IV instar larvae of a susceptible strain of Aedes aegypti (CIPEIN strain) was used in laboratory assays. The "Mosquito Dunks" at recommended use dosis (14,4 mg / 100 cm2 surface) were assayed for residual activity. 100% mortality was found for at least 180 days (6 month) with 48 hs larvae exposition. The results presented in this work suggests that this new solid slow release formulation of Bti with more residual activity could be a good alternative for Temephos for Aedes aegypti larvae control, specially for those cases in which resistance to the organophosphorus compound is reported. Keywords: Mosquito, Aedes aegypti, Control, Bacillus thuringiensis, Dengue.