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- Title
Effect of a mixture of iprobenfos and malathion on the development of malathion resistance in the mosquito Culex pipiens pallens Coq.
- Authors
Li-Ming Tao; Jian-Zhong Yang; Pei-Jun Zhuang; Zhen-Hua Tang
- Abstract
A malathion-resistant (RM) strain of Culex pipiens pallens Coq was obtained by successively selecting a field population with malathion in the laboratory. The synergistic effect of iprobenfos on malathion toxicity and α-naphthyl acetate (α-NA) esterase assay revealed that malathion resistance in the RM strain was associated with increased α-NA esterase activity and the synergism was mainly due to the inhibition by iprobenfos of this activity. There was no difference in α-NA esterase activity between the larvae and female adults in the susceptible (S) strain, but the activity in the adults was 13-fold higher than in the larvae of the RM strain. To understand the effect of the application of a mixture of iprobenfos and malathion on the evolution of malathion resistance, an artificial strain (Syn) was generated by mixing the RM and S strains with 0.1 frequency of the malathion-resistant individuals. The offspring of the Synstrain were divided into two substrains, Rm and Rm+ibp, which were successively treated with, respectively, malathion alone and malathion + iprobenfos (1:2) at LC70. In the mixture, the fungicide iprobenfos acted as a synergist of malathion. After treatment for 10 generations, the resistance level to malathion was 317.4-fold for the Rm sub-strain, whereas for the Rin+ibp sub-strain it was only 38.9-fold, compared with the Syn strain. Similar results were obtained by measurement of α-NA esterase activity from both larvae and female adults. The α-NA esterase activities in larvae and female adults at F10 generation were 2.6- and 10.9-fold from the Rm+ibp sub-strain and 5.7- and 98.5-fold from the Rm sub-strain, respectively, compared with the Syn strain. The above results suggested that iprobenfos, although it cannot completely stop or prevent the onset of malathion resistance, could dramatically delay its evolution.
- Subjects
CULEX pipiens; MALATHION; CHOLINESTERASE-inhibiting insecticides; BIOLOGICAL assay; ORGANOPHOSPHORUS compounds; DEVELOPMENTAL biology; LARVAE; WOOD preservatives; MOSQUITOES
- Publication
Pest Management Science, 2006, Vol 62, Issue 1, p86
- ISSN
1526-498X
- Publication type
Article
- DOI
10.1002/ps.1125