| The chemical control is still playing an unsubstituted role in pest control. However, since the pest control has been unduly depended upon insecticides which sometimes are used irrationally for a long time, the pests have successfully adapted to most of the insecticides by becoming physiologically and/or behaviorally resistant to them. Insecticide resistance is now a complex problem involved in the pest control. German cockroach, Blattella germanica, as a domiciliary pest, is so highly dependent on humans for survival that it is one of the pests with high public health importance. And its invasion scope is spreading from some special areas, such as hotels, hospitals, and groceries so on, to homes. Therefor, it has become one of the uppermost control obsjects of the pests in cities. Since 1950s, the method of German cockroach control has gradually been turned to chemical ways. Unfortunately, frequent and extensive application of a variety of insecticides, such as organochlorines, organophosphates, carbamates, and pyrethroids for control of German cockroach, has resulted in the emergence and development of insecticide resistance in some field populations. It doubtless brings a big challenge to control program.For the purpose of the rational usages of insecticides and improvement the effort of control, an evaluation of the resistance level of field populations of German cockroaches to commonly used insecticides was made by comparing them with that of susceptible population. F, offspring of adult male cockroaches (2~3 weeks old) delivered by the field populations, namely TZ, XY, WJ and HH population, under standard condition (25℃±1 ℃ and 65%±5% RH) were used in the tests.The glass residual bioassay was performed in this study. Permethrin(0.05% industrial dose) and propoxur (0.03% industrial dose) were prepared respectively in acetone solvent and 1ml was pipetted into each 0. 3-liter experimetal glass jar (the mean of inner surface area is about 240cm2). The dosage of insecticides used was 0.50 mg for permethrin or 0. 30 mg for propoxur per jar. Time to 50% knockdown (KT5(I) was determined by using the probit-logit option of Probit2 of the time-mortality program under Mathematica 3. 0. Resistance ratios were estimated by comparing the resistance level of field populations with that of the susceptible population. The results showed that the resistance of the four field populations to both permethrin and propoxur were in different levels, the resistance ratios ranged from 3. 63 ~ 8. 73 and 1. 26 -1. 84 for permethrin and propoxur respectively.Corresponding biochemical assays were selected on the basis of the bioassay results. The total cytochrome P450 content of the whole microsomal resuspension was tested by CO-difference spectra and nonspecific esterase activity was measured with p-nitrophenyl acetate (PNPA) as the substrates. Nonspecific esterase activity and total cytochrome P450 content of each field population were compared with that of the susceptible population respectively through the program of the Repeated Measures Analysis. Significant difference of nonspecific esterase activity occurred in JZ and WJ stains when compared with that of in susceptible population, and did not occur in HH and XY populations. With a view of bioassay result that there were relatively higher resistance ratios to permethrin in JZ and WJ populations, it was consistent with that of biochemical assays results. According to the results, the nonspecific esterase-based resistance mechanism was involved in permethrin resistance in JZ and WJ populations. Statistical difference occurred in total cytochrome P450 content among the 4 field populations when compared with that of in the susceptible population. The rank of total cytochrome P450 content by population (and magnitude of difference over the susceptible population) was JZ (4.88-fold), WJ (3.88-fold), XY (2.13-fold), and HH (2. 00-fold). According to the earlier findings and current study result, permethrin resistance might be correlated with total cytochrome P450 con...
|
PDF Full Text Request