author(s)
Barry Borkeum Raoul, Ngakou Albert, Tamò Manuele and Nukenine Elias Nchiwan

abstract
The ability of Azadirachta indica aqueous extract and the mycoinsecticide Metarhizium anisopliae interactions in controlling the cowpea thrips (Megolurothips sjostedti) was compared in the field grown Vigna unguiculata at Dang, Ngaoundere-Cameroon. The field trial was arranged in a completely randomized block design with five treatments, each of which was replicated four times. The five treatments included the control and the four tested insecticide products. V. unguiculata plants were sprayed three times at flowering stage with the insecticide products at five days interval. The parameters taken into account were adult thrips counts after three sprays, the number of cowpea plant ramifications, the number of dry pods, and the weight of dry grains at harvest. All the tested insecticides significantly reduced the M. sjostedti population, with the efficiency grade A. indica < M. anisopliae < A. indica + M. anisopliae < Decis®. Insecticides applications also increased V. unguiculata grain yields, with effectiveness similar to that of thrips populations, although Decis® and the combination A. indica + M. anisopliae had the same effect. There was a strong inverse linear correlation between grain yield and thrips population size (R² = 0.96). M. anisopliae and A. indica induced more ramifications in V. unguiculata than Décis® and the combination A. indica + M. anisopliae. Our results suggest that the combination A. indica + M. anisopliae could be considered as a potential insecticide in the management of thrips in V. unguiculata fields. This would increase V. unguiculata grain yields, alleviate hunger and malnutrition as well, and reduce environmental impact of residual synthetic chemical insecticides such as Decis®.