| Abstract: |
Development of resistance to the developmental insecticides chlorfluazuron and flufenoxuron, and the bioinsecticide Bacillus thuringiensis aizawai (Xentari) in the newly hatched larvae of the pink bollworm Pectinophora gossypiella (Saunders) (laboratory and field colonies) was investigated under the laboratory conditions.Resistance ratios of chlorfluazuron in the laboratory and field strains ranged between 3.3- to 1022.3- , and 2.4- to 342.37-fold, respectively. The corresponding figures of flufenoxuron ranged between 2.7- to 489.9- , and 1.1- to 209.6- fold. With Xentari, the resistance ratios in the field strain ranged between 1.9 – and 81.4 – fold. The rate of building up of resistance was faster in the laboratory strain than with the field one. Chlorfluazuron exhibited higher capacity in the rate of building up of resistance in both colonies.Cross resistance between both chlorfluazuron -, and flufenoxuron – resistant field strains and some recommended insecticides such as carbaryl, thiodicarb, chlorpyrifos (Dursban 48%), chlorpyrifos (Octafos 48%), cypermethrin, tebufenozide, Xentari 10.3% WDG ( Bacillus thuringiensis) and Spinosade 24% SC (Saccharopolyspora spinosa) was not apparent. While, slight cross resistance was observed between chlorfluazuron and flufenoxuron – resistant field strains, and between flufenoxuron and chlorfluazuron – resistant field strain; the resistant ratios were 40.1 -, and 39.1 – fold, respectively. Quick reversion to susceptibility was observed with the flufenoxuron – resistant field strain when it was left for three generations without selection, the resistance ratios reduced from 236.0 – to 5.6 – fold. Slight reversion to susceptibility was observed with the chlorfluazuron – resistant field strain the resistance ratios reduced from 433.74 – to 377.37 – fold. Resistant to chlorfluazuron and flufenoxuron have a distinct latent effects on the larval, and pupal durations, adult longevity, sex ratio, reproductive potential. The results suggest that chitinase play an important role in chlorfluazuron and flufenoxuron resistance, while, protease play a role with B. thuringiensis (Xentari) resistance. Transverse section by electronic microscope showed that chlorfluazuron disturbed the components of the procuticle layer, such deformities was absent in the resistant strains.
|
|
|