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
Minista Issa
Plant Production and Protection Unit, Department of Biological Sciences, Faculty of Science, University of Ngaoundere, P.O.Box 454, Ngaoundere, Cameroon.
Albert Ngakou *
Plant Production and Protection Unit, Department of Biological Sciences, Faculty of Science, University of Ngaoundere, P.O.Box 454, Ngaoundere, Cameroon.
Christophe Laba Haouvang
Plant Production and Protection Unit, Department of Biological Sciences, Faculty of Science, University of Ngaoundere, P.O.Box 454, Ngaoundere, Cameroon.
Elias N. Nukenine
Applied Zoology Laboratory, Department of Biological Sciences, Faculty of Science, University of Ngaoundere, P.O.Box 454, Ngaoundere, Cameroon.
*Author to whom correspondence should be addressed.
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).
Keywords: Cylas puncticolis, Ipomoea batatas, arbuscular mycorrhiza fungi, aqueous neem leaves extract, damages severity, crop yield