Pesticide resistance in Plutella xylostella (Lepidoptera: Plutellidae) populations from Togo and Benin

Abstract

AbstractThe diamondback moth,Plutella xylostella(L.) is the major insect pest of cabbage crops in Togo and Benin. For control, farmers very often resort to spraying chemical insecticides at high dosages with frequent applications. Bioassays were carried out on three populations ofP. xylostella, two from Togo (Kara and Dapaong) and one from Benin (Cotonou), to assess their level of susceptibility to currently used insecticides. A reference strain ofP. xylostellafrom Matuu in Kenya was used as a control. In the laboratory, three insecticide representatives of different chemical families (deltamethrin, chlorpyrifos ethyl and spinosad) were assayed against third instar larvae ofP. xylostella. Results revealed thatP. xylostellapopulations from Dapaong, Kara and Cotonou were more resistant to deltamethrin (13 to 59-fold at LC50level, 149 to 1772-fold at LC90level) and chlorpyrifos ethyl (5 to 15-fold at LC50level, 9 to 885-fold at LC90level) than the reference strain. Spinosad was more toxic toP. xylostellapopulations than the other insecticides with LC50and LC90values less than 1 µg/ml and 15 µg/ml, respectively. However, the population from Cotonou appeared significantly more resistant to spinosad compared to the reference strain. These results are discussed in the light of developing an integrated pest management strategy for reducing the selection pressure of spinosad.