bifenthrin and chlorpyrifos-methyl

The efficacy of mosquito nets treated with bifenthrin (pyrethroid) and chlorpyrifos-methyl (organophosphate), alone and in mixture, was evaluated against the pyrethroid-resistant strain (VKPR) of Anopheles gambiae using the tunnel test technique. Results first showed that bifenthrin and chlorpyrifos-methyl kept a good excito-repellency effect against resistant mosquitoes despite the low doses applied on nets. With the mixture, irritancy significantly increased, which consequently limited the duration of exposure of females to impregnated surface. This phenomenon most probably explained the absence of synergism between bifenthrin and chlorpyrifos-methyl concerning the insecticidal activity of this mixture. This study demonstrated the importance of the mosquito behaviour in the global effectiveness of insecticide treated materials and in the development of alternative strategies for vector control. Concerning the prospective insecticide mixtures, not only will we have to consider the insecticidal properties of each insecticide selected, but also their excito-repellency which affects the time of duration of mosquitoes on the treated surface.

Topics: Animals; Anopheles; Bedding and Linens; Behavior, Animal; Chlorpyrifos; Cholinesterase Inhibitors; DDT; Drug Resistance, Multiple; Drug Synergism; Insect Vectors; Insecticide Resistance; Insecticides; Malaria, Falciparum; Mosquito Control; Protective Devices; Pyrethrins

The efficacy of a binary mixture of bifenthrin (pyrethroid) and chlorpyrifos-methyl (organophosphate) has been tested against susceptible and pyrethroid-resistant strains of Anopheles gambiae Giles, the major malaria vector in sub-Saharan Africa. Dose-mortality regression lines were determined for each insecticide alone and in mixtures by topical applications on adult female mosquitoes. A combination index (CI) was used to quantify the interactions occurring between the pyrethroid and organophosphate insecticides. The results revealed synergism at high doses against both susceptible (0.7 > CI > 0.3) and pyrethroid-resistant (0.9 > CI > 0.7) An. gambiae. These results suggest that insecticide mixtures may be an alternative strategy for vector control, especially in areas where mosquitoes are resistant to pyrethroids.

Topics: Animals; Anopheles; Chlorpyrifos; Female; Insecticide Resistance; Insecticides; Mosquito Control; Pyrethrins

In order to prevent the resistance of Anopheles gambiae s.l. to pyrethroids from spreading too quickly and to lengthen the effectiveness of insecticide impregnated mosquito nets, it has recently been suggested to use mixtures of insecticides that have different modes of action. This study presents the results obtained with tulle mosquito nets treated with bifenthrin (a pyrethroid) and chlorpyrifos-methyl (an organophosphorous) both separately and in mixture on two strains of An. gambiae, one sensitive to all insecticides, and the other resistant to pyrethroids. The values of KDt50 and KDt95 and the mortality induced with the mixture of bifenthrin (25 mg/m2) and chlorpyrifos-methyl (4.5 mg/m2) show a significant synergistic effect on the strain of An. gambiae susceptible to insecticides. However, the tested combination does not induce any synergistic effect on the VKPR strain selected with permethrin, but only enhances the effectiveness of the two insecticides taken separately.

Topics: Animals; Anopheles; Bedding and Linens; Chlorpyrifos; Dose-Response Relationship, Drug; Drug Synergism; Insect Vectors; Insecticide Resistance; Insecticides; Malaria; Mosquito Control; Organophosphorus Compounds; Pyrethrins; Treatment Outcome

The efficacy of bifenthrin (0.5 mg/kg) + piperonyl butoxide (7 mg/kg) + chlorpyrifosmethyl (10 mg/kg) against beetle and psocid pests of sorghum was evaluated in silo-scale trials in southeast Queensland, Australia. The pyrethroid bifenthrin was evaluated as a potential new protectant in combination with the organophosphate chlorpyrifos-methyl, which is already registered for control of several insect pests of stored cereals. Sorghum (approximately 200 metric tons) was treated after both the 1999 and 2000 harvests and sampled at intervals to assess treatment efficacy and residue decline during up to 7 mo of storage. Generally, test strains of the beetles Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L), and Cryptolestes ferrugineus (Stephens) were prevented from producing live progeny for up to 7 mo. The treatment failed against one strain of R. dominica known to be resistant to bioresmethrin and organophosphates. Two malathion-resistant strains of O. surinamensis were marginally controlled with 94-100% fewer adult progeny produced. For psocids, no strains of Liposcelis bostrychophila Badonnel, Liposcelis decolor (Pearman), or Liposcelis paeta Pearman produced live progeny, although the control of a field strain of Liposcelis entomophila (Enderlein) was generally poor. Results show that this treatment should protect sorghum for at least 7 mo against most prevalent strains of grain insect in eastern Australia, although control may be limited in areas in which L. entomophila or pyrethroid-resistant R. dominica are present.

Topics: Animals; Chlorpyrifos; Coleoptera; Drug Synergism; Insect Control; Insecticide Resistance; Insecticides; Pyrethrins; Sorghum