Objective To evaluate the insecticide resistance of Aedes albopictus in Tongchuan city and Ankang city of Shaanxi province, China. Methods Distinguishing dosage method was used to measure the mortality rates of Ae. albopictus larvae within 24 h of exposure to three insecticides; median lethal dose (LC ₅₀) method was used to measure the LC ₅₀ of nine insecticides for Ae. albopictus larvae. Results The distinguishing dosage method showed that Ae. albopictus in Ankang and Tongchuan had resistances to dichlorvos, permethrin, and deltamethrin. The LC ₅₀ method showed that for Ae. albopictus in Ankang and Tongchuan, the LC ₅₀ of β-cypermethrin was 0.003 71 mg/L and 0.001 45 mg/L, the LC ₅₀ of permethrin was 0.006 25 mg/L and 0.017 67 mg/L, the LC ₅₀ of deltamethrin was 0.002 69 mg/L and 0.000 76 mg/L, the LC ₅₀ of cypermethrin was 0.017 46 mg/L and 0.009 37 mg/L, the LC ₅₀ of DDT was 0.809 54 mg/L and 0.217 06 mg/L, the LC ₅₀ of dichlorvos was 0.040 15 mg/L and 0.026 77 mg/L, the LC ₅₀ of parathion was 0.002 22 mg/L and 0.003 10 mg/L, the LC ₅₀ of propoxur was 0.348 14 mg/L and 0.651 91 mg/L, and the LC ₅₀ of fenobucarb was 0.157 19 mg/L and 0.543 77 mg/L. Ae. albopictus in the two areas developed higher resistance ratios to dichlorvos, parathion, and propoxur than to other insecticides. Conclusion Insecticides should be used properly to control Ae. albopictus in a geographic area with certain ecological characteristics, so as to retard the development of insecticide resistance in Ae. albopictus.

Objective To understand the resistance of Musca domestica to insecticides in the four areas of Shaanxi province for providing evidence for scientific application of insecticides. Methods Insects were collected in the fields in urban areas where flies bred and sensitive insects were reared in laboratory without exposure to insecticides. Topical dropping method was used to determine the death rate by different drug concentrations, with LD ₅₀ obtained by POLO software analysis. Results The LD ₅₀ of sensitive insects to DDVP, temephos, DDT, propoxur, beta-cypermethrin, deltamethrin, cypermethrin and permethrin was 0.004, 0.113, 0.010, 0.214, 0.003 07, 0.000 63, 0.003 and 0.013 μg/♀, respectively. Different degrees of resistance of M. domestica to the eight commonly used insecticides were observed in Ankang, Weinan, Baoji, Tongchuan city of Shaanxi province. The LD ₅₀ of M. domestica in four areas to DDVP, temephos, DDT, propoxur, beta-cypermethrin, deltamethrin, cypermethrin and permethrin was 0.051-0.301, 4.429-14.480, 1.259-1.573, 13.579-33.556, 0.024-0.303, 0.017-0.046, 0.047-0.269 and 0.016-0.053 μg/♀, respectively, with the average LD ₅₀ to the eight insecticides from 0.028 to 23.549 μg/♀. The resistance ratio (R/S) was from 2.54 to 140.20, DDT being the highest and permethrin the lowest. Conclusion Insecticides should be applied scientifically to effectively curb the increase of resistance of M. domestica to the insecticides.

Objective To identify the resistance of Culex pipiens pallens to five commonly used insecticides in Xianyang city so as to provide evidence for control strategy development. Methods The mortality of larvae exposed to five insecticides was determined by the distinguishing dosage method. Results The resistance level of Cx. pipiens pallens was high under the diagnosis dose to DDT, DDVP, permethrin, and deltamethrin, and the mortality in 24 hours was 23.45%, 14.02%, 28.77%, 25.00%, respectively. The resistance to cypermethrin was moderate and the mortality was 58.63%. Conclusion The resistance of Cx. pipiens pallens to five commonly used insecticides in Xianyang has reached middle to high levels. Different kinds of insecticides should be used for control of mosquitoes.

Objective To determine the population composition, density and distribution of vectors in Yulin urban area, providing evidence for control of these insects. Methods Human baited net trap method and lamp baited trap method were employed for mosquito collection, cage-trapping for fly collection and sticky-paste for cockroach collection. Results Mosquitoes caught belonged to 5 species 4 genera, with Culex pipiens pallens being the dominant species. The average density based on the human baited net trap method was 19.11 per net per hour, or 1.61 per lamp per hour based on lamp baited trap method. The density in the urban area was higher than that in the villages. Flies belonged 23 species 19 genera 5 family, and the common species were Chrysomya megacephala, Lucilia sericata, Musca domestica, Muscina stabulans, Boettcherisca peregrine and L. cuprina, accounting for 36.49%, 20.41%, 14.78%, 10.61%, 8.65% and 2.61%, respectively. The average density was 4.42/ cage, the highest density observed in the farm produce markets. Cockroach density was 16.28/piece·night, highest observed in the restaurants, with Blattella germanica being the predominant species. The peak of flies and cockroaches was in August, and that of mosquitoes in July. Conclusion The population composition, density and distribution of vectors were basically grasped. Integrated measures should be taken with focus on such major areas as restaurants, farm produce markets and residential areas.

Objective To identify Musca domestica insecticide resistance in Xianyang city for proper application of insecticides. Methods Topical dropping method was used to determine the LD₅₀. Results The LD₅₀ values of DDVP, beta- cypermethrin, deltamethrin and propoxur for M. domestica were 0.019, 0.098, 0.013 and 6.627 μ g/♀, respectively. The resistances ratios (R/S) to four insecticides were 4.71, 31.92, 20.63 and 31.02, respectively. Conclusion The resistance of M. domestica in Xianyang city to four insecticides in Xianyang city has developed to varying degrees, particularly that to beta- cypermethrin and propoxur. Development of resistance may be due to improper administration of insecticides in the agricultural and construction areas. Additional resistance monitoring, proper use of insecticides and comprehensive vector control strategies are key to preventing the occurrence of drug resistance in these vectors.

Objective To evaluate the resistance in Culex pipiens pallens to commonly used insecticides in different areas of Shaanxi province. Methods Larval mortality for 4 insecticides and LC₅₀ of 8 insecticides determined via the dosing method and median lethal dose method, respectively. Results The resistance level of Cx. pipiens pallens in all five areas was high except the population in Yulin city, which had elementary resistance to permethrin. The LC₅₀ values for larvae to β - cypermethrin, permethrin, deltamethrin, cypermethrin, DDT, DDVP, parathion and propoxur were 0.001 82-0.012 24, 0.008 16-0.094 19, 0.000 58-0.005 59, 0.002 76-0.020 17, 0.100 96-1.296 86, 0.144 11-0.512 40, 0.001 47-0.007 06, and 0.234 60-1.182 37 mg/L, respectively. The highest resistance level to all pesticides was found in Baoji city, except for deltamethrin, cypermethrin and parathion, while the lowest level was found in Yulin city, except for parathion and propoxur. Conclusion The development of mosquito resistance was closely related with the use of insecticides. Therefore, it is important to ensure appropriate administration and regular resistance surveillance to defer and prevent the occurrence of resistance in mosquitoes.

【Abstract】 Objective To investigate the resistance of Culex tritaeniorhynchus to insecticides used frequently in high incidence areas of Japanese encephalitis in Shaanxi province. Methods The density of mosquitoes was calculated by labor hour method. Larva death rate of five insecticides and LC50 of eight insecticides were determined by distinguishing dosage method and median lethal dose method respectively. Results The average density of Cx.tritaeniorhynchus in breeding farm was 194.91/man· hour. The mortality of mosquitoes in Nanzheng, Hanyin, Hanbin and Pingli county was 1.84％-13.65％ and 10.86％-31.25％ after treatment by DDVP and deltamethrin for 24 h. Maximum LC50 of the same insecticide in different areas was1.27-8.00 times of the minimum. Conclusion Cx.tritaeniorhynchus developed different resistance to tested insecticides in four investigation sites, except that it was susceptible to cypermethrin in Hanbin, Nanzheng county and to DDT in Pingli, Nanzheng county. Cx.tritaeniorhynchus populations had developed high resistance to DDVP and deltamethrin, moderate resistance to permethrin. Rotational or mixed use of insecticides with different action mechanisms should be adopted to postpone the development of insecticide resistance.

Objective To investigate the composition and density of acaroid mites breeding in stored products of rural areas in Anhui province. Methods Acaroid mites were isolated by Waterflotation and Tullgren, and counted and identified under XTB microscope. Results 31 species of acaroid mites were isolated from 40 different stored products(700 samples), which were identified to 20 genera of 7 families. Acaroid mites can be checked out from each sample above all. The highest density (332.67±7.85)No./g was found in seasame, while the lowest was (13.43±5.28)No./g in hot peppers. In addition, Tyrophagus putrescentiae was most widely distributed and was found in 23 different stored products. Conclusion Many species of acaroid mites breeding in stored products are widely distributed and are seriously harm to stored products, so effective measures should be taken for control.