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Insect Resistance to Pyrethroids

Khandoker Azizul Islam
Department of Zoology, Unviersity of Dhaka, Bangladesh

David Orwin
Faculty of Science, Technology and Design, University of Luton, Park Square, Luton, Bedfordshire Lu1 3JU, U.K..

Bhupinder P. S. Khambay
Faculty of Science, Technology and Design, University of Luton, Park Square, Luton, Bedfordshire Lu1 3JU, U.K..

Abstract/ Executive Summary:

Two clones of Aphis gossypii (clone 171B of U. K. origin and clone Adana of Turkey origin) were reared and treated against Cypermethrin, Bifenthrin, Fenfluthrin, Deltamethrin, NRDC 196, BTG502 and RH63421. The pyrethroids were treated with two replications against topical application method and leaf dip method. Pyrethroids, BTG 502 and RH 63421 were confirmed as the high level of resistant strain (Turkey Adana) and susceptible strain (171B). The topical application gave more reproducible results with higher confidence limits than the leaf-dip method.

Keywords: Resistance, Aphis gossypii, Pyrethroids.

Location: Faculty of Science, Technology and Design, University of Luton, Park Square, Luton, Bedfordshire Lu1 3JU, U.K.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Insects

Objectives:

To assess the resistance of A. gossypii to pyrethroids.

Methodology:

Bio-assay methods were applied to assess the resistance of the insects throughout the work. The methods, such as topical application and leaf-dippings were useful in assessing the resistance levels in the laboratory. The two clones of A. gossypii cultures investigated were maintained without insecticide selection as anholocyclic clones derived from a single female in the original field samples. The aphids were reared routinely at a constant temperature of 20 ºC in the Laboratory in plastic boxes containing leaves excised from pumpkin (Cucurbita pepo). A number of measures was taken to prevent cross-contamination between clones. In addition to the isolation of the clones in different rooms, no two cultures were supplied with fresh plants on the same day. All plant materials removed from cages was bagged, deep-frozen and then incinerated. All glasshouse works were carried out prior to culture work, and the glasshouse was not re-entered till the next day. The pumpkin leaf discs (35 mm diameter) dipped in the aqueous solutions of insecticide (containing 0.01% agral surfactant) were placed upside down on an agar bed (25 mm in depth) in disposable plastic containers (30 mm high) and allowed to air-dry. The apterous adult aphids (10 per container; 3 batches per concentration) were then placed onto the treated leaf surface and confined by applying a ring of fluon to the exposed lip of the container. Results for at least two independent bioassays with insecticides were pooled and subjected to probit analysis using the POLO computer program (LeOra Software, Berkeley, CA). For comparison of results, the resistance factor (RF) was calculated for each compound as follows: Resistance Factor: LD₅₀(μg per aphid) of resistant strain / LD₅₀(μg per aphid) of susceptible strain, % mortality = (Some of mortality in three replicates / Total number tested per concentration) x 100.

Source of Information: Bangladesh J. Zool. 34(2): 173-179, 2006

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Results from a range of compounds against the susceptible and resistance strains of the following observations can be made: Both the susceptible and resistant strains of A. gossypii tested exhibited high levels of resistance (i.e., high RF values) and RFs for all the compounds tested fell within a narrow range. Thus no relationship between structure and RFs could be discerned. This is in contrast to observations with super-kdr insect species where significant differences have been observed. B. The two compounds BTG502 and RH63421, representing two distinct chemical classes (alkylamide and dihydropyrazole, respectively), are also highly resisted by the resistant strain of A. gossypii (adana) tested in this study. So from the results it is clear that there is a variation in resistance factors to pyrethroids in two clones of A. gossypii. This may be due to the increased level of detoxifying enzymes, (e.g. esterases) produced by adana, that modifies the pyrethroids to inactive metabolites. Esterase modifications in resistant strains of A. gossypii have been noted and have been claimed to be responsible for resistance. It can therefore be concluded that pyrethroid resistance in adana is an autosomally inherited, largely recessive trait. No decrease in the degree of resistance of adana to pyrethroids was observed from previous work by Xiaowen (2001) (unpublished) in the laboratory at Rothamsted, implying a high level of homozygosity for the resistance gene(s) in this strain.

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