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Effects of Formulated Imidacloprid on Two Mite Pathogens, Neozygites Floridana (Zygomycotina: Zygomycetes) and Hirsutella Thompsonii (Deuteromycotina: Hyphomycetes)

  • Surenda K. Dara
  • Fabien C. C. HountondjiEmail author
Research Article

Abstract

Neozygites floridana (Weiser & Muma) Remaudière & Keller and Hirsutella thompsonii Fisher are important fungal pathogens of mites on cassava in Benin. Bioassays were conducted to evaluate the influence of four concentrations (50, 100, 200 and 500 ppm) of a water-dispersible formulation (Gaucho 70 WS) of imidacloprid on the conidial germination of these two fungi. Imidacloprid significantly reduced the germination of primary conidia and formation of infective capilliconidia in N. floridana. In contrast, imidacloprid concentrations of 100 ppm and above increased conidial germination in H. thompsonii. Another bioassay was conducted to evaluate possible synergism between imidacloprid and H. thompsonii in the mortality of the cassava green mite, Mononychellus tanajoa (Bondar). Hirsutella thompsonii alone and in combination with imidacloprid both killed around 95% of the mites after five days. In contrast, the mortality of mites treated with imidacloprid alone was close to that of untreated mites, which was around 30% on the fifth day after treatment.

Key Words

imidacloprid Mononychellus tanajoa Neozygites floridana Hirsutella thompsonii synergism 

Résumé

Neozygites floridana (Weiser & Muma) Remaudière & Keller et Hirsutella thompsonii Fisher sont des champignons pathogènes des acariens du manioc au Bénin. Des essais ont été conduits afin d’évaluer l’influence de quatre différentes concentrations (50, 100, 200 et 500 ppm) de la formulation en poudre hydrosoluble de l’insecticide imidacloprid sur la germination des conidies des deux champignons. Les résultats prouvent une action spécifique de l’imidacloprid sur chacun’des deux champignons. La germination des conidies primaires et des capilloconidies de N. floridana est significativement affectée, alors que chez H. thompsonii, le pourcentage de germination est significativement plus élevé aux plus fortes concentrations. Vu ces résultats, de nouveaux essais ont été entrepris pour évaluer une éventuelle synergie de l’imidacloprid et de H. thompsonii pour lutter contre l’acarien vert du manioc, Mononychellus tanajoa Bondar. Comparativement au traitement à l’imidacloprid seul, la mortalité est significativement plus élevée chez les acariens traités avec H. thompsonii seul ou avec la combinaison imidacloprid-H. thompsonii. L’efficacité entre ces deux derniers traitements est comparable.

Mots Clés

imidacloprid Mononychellus tanajoa Neozygites floridana Hirsutella thompsonii synergisme 

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Copyright information

© ICIPE 2001

Authors and Affiliations

  1. 1.Plant Health Management DivisionInternational Institute of Tropical AgricultureCotonouBenin

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