Traitements insecticides et dynamique des populations de Bemisia tabaci Gennadius en culture cotonnière au Burkina Faso

Abstract

Considéré dans le passé comme un ravageur secondaire, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) est devenu depuis la campagne agricole 1997-1998 un des ravageurs importants en culture cotonnière au Burkina Faso. La mise en place d'une méthode de lutte efficace contre B. tabaci passe nécessairement par une meilleure connaissance de la biologie de ce ravageur. L'objectif de cette étude est, d'une part de développer une technique d'échantillonnage rapide des larves, d'autre part de suivre les effectifs de B. tabaci sur deux sites de l'ouest du Burkina Faso (Boni et Farako-Bâ). Les résultats obtenus dans cette étude montrent que les larves de B. tabaci sont plus importantes sur les feuilles basales des branches 3, 4 et 5 numérotées de haut en bas. Sur chaque feuille, les lobes délimités par les deux nervures latérales (B et C) représentent la zone de prédilection des formes larvaires de B. tabaci. L'étude de la dynamique des populations de B. tabaci montre que les traitements chimiques ne semblent pas avoir d'effet. Ils pourraient même avoir un effet favorable sur le développement du ravageur. Les dégâts observés sont faibles et aucune différence n'est observée entre les champs traités et non traités. L'ensemble des résultats obtenus dans cette étude a permis d'avoir quelques renseignements sur la biologie de B. tabaci, ce qui devrait constituer une avancée notable dans l'élaboration d'une stratégie de lutte contre ce ravageur au Burkina Faso. Abstract Insecticides and dynamics of Bemisia tabaci Gennadius populations in cotton fields of Burkina FasoRegarded in the past as a secondary pest, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) has since the 1997-1998 cropping season become one of the most significant pests in the cotton fields of Burkina Faso. The implementation of an effecient control strategy against B. tabaci necessarily implies a better knowledge of the biology of this pest. The objective of this study is to develop a fast technique for the sampling of the larvae on the one hand and to follow the biology of B. tabaci in two sites of western Burkina Faso (Boni and Farako-Bâ) on the other hand. The results obtained show that the larvae of B. tabaci are more important on the basal leaves of branches 3, 4, and 5. On each leave, lobes B and C are the zones B. tabaci larvae are most partial to. The survey of the dynamics of B. tabaci populations shows that chemical treatments seem to have no impact on the total number of B. tabaci. They may even have a favourable effect on the development of the pest. Moreover, the damage observed is slight and no difference is found between treated and untreated fields. The overall results of this study provide some information as to the biology of B. tabaci and should pave the way for the development of an efficient integrated control strategy against this pest in Burkina Faso.

Distribution of Bemisia tabaci (Homoptera: Aleyrodidae) biotypes and their associated symbiotic bacteria on host plants in West Africa

“…This situation had already been observed among the B and Q biotypes, the latter excluding the former in the context of insecticide treatment (Chu et al, 2010;Crowder et al, 2010). The same phenomenon may occur in Western Africa among resistant Q and susceptible ASL biotypes, explaining (Gnankine´et al, 2007). However, in the localities where we sampled twice, in 2007 and in 2009, the prevalence of these biotypes was similar.…”

“…, 2010). The same phenomenon may occur in Western Africa among resistant Q and susceptible ASL biotypes, explaining why the sensitivity of adult populations of B. tabaci can vary greatly from one place and 1 year to another in Burkina Faso (Gnankiné et al. , 2007).…”

Detection of genetically isolated entities within the Mediterranean species ofBemisia tabaci: new insights into the systematics of this worldwide pest

“…The mutation that confers resistance to organophosphates was found in both Q1 and ASL, but, while this resistant allele was almost fixed in Q1 [mean 0.98, standard error (SE) 0.02], its frequency was intermediate in ASL (mean 0.59, SE 0.08). The high selection pressure due to the repetitive organophosphate treatments applied in western Africa, particularly on cotton and vegetables, has probably driven the spread of this mutation. On the other hand, while the resistant mutation on the para ‐type voltage‐gated sodium channel gene that confers resistance to pyrethroids was also almost fixed in Q1 populations, it was rarely detected in ASL.…”

“…In B. tabaci , two mutations in the para ‐type voltage‐gated sodium channel gene, L925I and T929V, and one mutation in the acetylcholinesterase enzyme ace1 (F331W) confer resistance to pyrethroids and organophosphates respectively . Previous studies have shown that the use of these insecticides results in the development of resistant B. tabaci populations, which is undermining the current management of this pest …”

Abundance of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and its parasitoids on vegetables and cassava plants in Burkina Faso (West Africa)

“…In 1998, outbreaks were recorded in cotton fields in Burkina Faso, Mali, and Côte d'Ivoire inducing severe crop damages (Otoidobiga, Vincent, & Stewart, ). The resulting losses severely impacted the economic activity of these countries (Gnankiné, Traore, Sanon, Traore, & Ouédraogo, ). Nowadays B. tabaci has been reported in all tropical and subtropical regions.…”