author(s)
Issa Minista, Albert Ngakou, Lame Younoussa and Elias Nchiwan Nukenine

abstract
The insecticidal efficacy of neem in storage at Dang (Ngaoundere) and Kismatari (Garoua) was investigated in the present study under controlled conditions for two consecutive years (2013, 2014). In each of the studied site and and during each year, a factorial fully randomized block design ((3x2) x 4) was adopted, with two varieties (local and TIB1) as the first factor, and treatments (Neem oil, Neam leaves Extract, Control) as the second factor, each of which was repeated four times. The rate and severity of attacks, as well as the population dynamic of Cylas puncticollis were assessed. Results indicate that, after 2 months of storage, neem oil has proven to be the best bi-oinsecticide to preserve the two varieties of sweet potato grown in storage, causing 100% mortality of the weevils, and 0% attack of tubers. The neem leaves extract also significantly (p<0.001) reduced the number of holes inflicted to tubers in storage by 2.46 and 2 folds in 2013, 1.64 and 1.7 folds in 2014 for the local variety, by 2.21 and 2.2 folds in 2013, 1.8 and 1.8 folds in 2014, respectively at Kismatari-Garoua and Dang-Ngaoundere compared to the controlled tubers. The improved sweet potato variety TIB1 was the most attacked by C. puncticollis, with average attack rates of 57% and 56% respectively at Kismatari-Garoua and Dang-Ngaoundere against 39% and 40% for the local variety. Refering to these results, neem oil could be applied by farmers as an alternative control measure to effectively control the sweet potato weevil (C. puncticollis) in storage.