Impact of pest management practices on the frequency of insecticide resistance alleles in Bemisia tabaci (Hemiptera: Aleyrodidae) populations in three countries of West Africa

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Résumé

In West Africa, the use of organophospates and pyrethroid insecticides to control cotton pests has led to the
evolution of resistance in field populations of Bemisia tabaci Gennadius. Three pest management programs have
been commonly recommended: the Conventional Program (CP) where 6 treatments are applied, the use of Bt
cotton plants for which only 2 applications of neonicotinoids are required and that has been adopted in many
countries, and a biological program (BP) without any chemical treatment. The present study aimed to determine
the influence of these practices on the frequency of mutations that confer resistance to pyrethroids (mutation
L925I in the para-type voltage-gated sodium channel gene) and organophosphates (mutation F331W in the
acetylcholinesterase enzyme ace1: allele Ace1R) in B. tabaci populations using Bt cotton and CP areas in Pô and
Saria (Burkina Faso), CP and BP areas in Kandi (Benin) and only CP areas in Tové and Infa (Togo). All individuals
sampled belonged to the MED (biotypes MED-Q1) and Africa Silver Leafing (ASL) species. MED-Q1 was found in
sympatry with ASL in Burkina Faso both on CP and Bt cotton areas at variable frequencies. In Togo and Benin,
only ASL was found, except in Tové where MED-Q1 was also detected, but at low frequency. Frequencies of
mutations that confer resistance varied between localities and species but we did not find any strong evidence of
a relationship between the pest management program and these frequencies except for the allele Ace1R in
Burkina Faso for which the frequencies decrease when chemical applications are reduced. This study provides
valuable information for the development of efficient integrated pest management programs.

Mots-clés

Pest management programs, Insecticides, kdr, Ace1R , Bemisia tabaci