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


Abstract: Helicoverpa armigera (Hübner), a polyphagous moth, is the major cotton pest inAfrica. Larvae feed on bolls, flowers and squares, seriously reducing yield. To reduce the use ofinsecticides and to improve the management of this cotton pest, there is a growing interest inreinforcing the landscape’s suppressive properties. The aim of this study was to determine ifmoth abundance and larval infestation differs among landscapes with different composition(diversity of crops, proportion of bush) to test for a landscape effect on Helicoverpa armigeraabundance during peak infestation. In five cotton fields in four landscapes differing in land cover(cotton, cotton + maize, cotton + tomatoes, cotton + bush), measurements of larval infestationwere made four times from September 23th to October 18th 2011. Additionally, adult mothabundance was established using light trapping from September 24 to 1st November in the fourlandscapes plus one landscape without any cotton field in the area of the W National Park. Larvalinfestation was significantly higher in the fields previously cultivated with tomatoes. Results oflight trapping of moths did not reveal differences among the landscapes except in the landscapein the W National Park where no moths were trapped. This finding suggests that cottoninfestation by Helicoverpa armigera could be related to the proximity of market gardening.Subsequent analyses (analytical chemistry and molecular biology) are underway to investigatethis hypothesis.

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