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Is there a landscape effect on moth pest (H. armigera ) abundance and infestation rate in cotton fields in North Benin?

Tsafack Menessong N., Menozzi P., Brévault T., Deconchat M., Ouin A.. 2012. IOBC/WPRS Bulletin, 75 : p. 191-195. Meeting of IOBC-WPRS Working Group "Landscape Management for Functional biodiversity". 5, 2012-05-07/2012-05-10, Lleida (Espagne).

Helicoverpa armigera (Hübner), a polyphagous moth, is the major pest of cotton crops. Larvae feed on capsules, flowers and flower buds of cotton, severely reducing the yield. In order to reduce the use of chemicals and to improve the management of this cotton pest, there is a growing interest in reinforcing the landscape suppresiveness property to limit the damages caused by Helicoverpa armigera. The aim of this study was to determine if moth abundance and larval infestation will differ among landscapes presenting different composition (diversity of crops, proportion of bush) to test for a landscape effect on Helicoverpa armigera abundance during the infestation peak. In Five cotton fields in four landscapes (mainly cotton, cotton+maize, cotton + tomatoes, cotton + bush), measures of larvae infestation were conducted four times, from September 23 to october18Additionally, adult moth abundances were evaluated using light trapping from September 24 to 1st November in the four landscapes plus one landscape without any cotton field in the area of the W National Park. Larval infestation was significantly higher in the landscape C (landscape-cotton crops near tomatoes). However, results of light trapping of moths did not exhibit any differences among the landscapes except in the landscape in the W National Park where no moth were trapped. This finding suggests that cotton field infestation of Helicoverpa armigera could be related to the proximity of market gardening. Subsequent analyses (analytical chemistry and molecular biology) are underway to support or refute this hypothesis.

Mots-clés : helicoverpa armigera; gossypium; paysage; bénin

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