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Cirad

Nouveaux essais de terrain d'un myco-insecticide destiné à la lutte contre les criquets au Brésil (10 novembre au 22 décembre 2002)

Lecoq M., Foucart A., Tavares da Silva J.B.. 2003. Montpellier : CIRAD-AMIS, 20 p.. numero_rapport: CIRAD-AMIS N° 74/2002.

The current experiments have been conducted within the framework of a joined project EMBRAPA CIRAD whose objective is to limit the use of chemical insecticides for the control of locusts and grasshoppers, and to assess in the field the efficacy (and inocuity for non target fauna) of a myco-insecticide containing the fungus Metarhizium anisopliae var. acridum. In November and December 2002, field trials have been conducted in Mato Grosso. The absence of hopper bands of Rhammatocerus schistocercoides, now apparently in recession, obliged to assess the effects of the mycopesticide only on non target grasshoppers and non target arthropods in general and to compare these effects with a classical pesticide (fenitrothion). The experimental device consisted of three plots of 4 hectares, one as control, one sprayed with the mycopesticide (3,8x10E12 spores/ha) and the third with fenitrothion (Sumithion CE at 342 gma/ha). With the fenitrothion the mortality was 94 and 78% at 6 days post treatment respectively for nymphs and adults; then the grasshopper population recover, but very slowly. With the mycopesticide the mortality rate was 46% at 22 days post treatment for the nymphs, but only 10% for the adults. The global mortality rate (nymphs and adults) is 88% at 6 days for fenitrothion and 30% at 16 days for the mycopesticide. This low mortality rate (50% was at least expected for the whole population considering previous experiments) is certainly the result of application and formulation problems. Concerning the non target arthropods, the samples have not been analysed yet. A final report will be written after a complete data analysis.

Mots-clés : rhammatocerus schistocercoides; lutte anti-insecte; lutte biologique; metarhizium anisopliae; expérimentation au champ; efficacité; faune; mato grosso; brésil; metarhizium anisopliae var. acridum

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