Potentials of Arbuscular Mycorrhiza Fungi (AMF) and Neem (Azadirachta indica A. Juss.) Leaves Extract as Biological Control Agents against the Sweet Potato Weevil (Cylas puncticollis Boh.) in Two Agro-ecological Zones of Cameroon

Abstract

Sweet potato [Ipomea batatas (L.) Lam.] ranks second in production and value after cassava among the root crops in Cameroon. Its production has been declining mainly due to the damaging effects of Cylas puncticolis Boheman (Coleoptera: Apionidae), its primary pest. Therefore, this study was carried out to determine the effectiveness of Arbuscular Mycorrhiza Fungi, aqueous neem leaves extract and synthetic chemical fertilizer-NPK against C. puncticolis. The experiment was conducted under field conditions at Garoua and Ngaoundere, respectively in the agro-ecological zone I and II, and during the two consecutive cropping seasons of 2013 and 2014. Results indicate that, whereas  mycorrhiza improved the stem length by 58 and 64%, the combination neem-mycorrhiza did so by 59 and 66%, respectively for the local and the TIB1 sweet potato varieties compared to treatment control that weakly enhanced the stem length. Neem-mycorrhiza and Arbuscular Mycorrhiza alone in this order contributed to a significant (p < 0.05) reduction of damages caused to the local sweet potato variety by C. puncticollis within the two agro-ecological zones. Among the cultivated varieties used in the field, the local variety proved to be more resistant to pest infestations, despite its low yield (12.65 t/ha) compared to the improved variety TIB1 (15.82 t/ha).