Effectiveness of cultural practices and sweet potato varieties (Ipomoea batatas Lam) in managing sweet potato weevil (Cylas spp) in Zanzibar

Field experiments were conducted simultaneously from April to July 2012 at agro- ecologies; Bambi (Latitude 06 o 09’S, Longitude 039 o 16’E; and Altitude 20m above sea level) Central District and Kizimbani (Latitude 05 o 54’S, Longitude 039 o 16’E; and Altitude 20 m above sea level) Western Unguja district. The aim was to investigate the effectiveness of selected cultural practices (weeding and hilling-up once, twice and thrice), vine portions (apical, middle and basal) and variety (Mbirimbi, Shangazi and Mayai) on damage due to sweet potato weevil. The experiments were laid out in split-split in a randomized complete block design with three replications. The main plot factor was three varieties, the sub plot factor was three vine portion and the sub-sub plot factor was cultural practices. The main plots were consisted of twenty seven, sub plots nine while sub-sub plot three ridges. The vines were planted at a spacing of 0.3 m apart on a ridge of six metre long and one metre apart. Weeding and hilling-up the soil were done simultaneously at four weeks, eight weeks and twelve weeks after planting. Data collected were sweet potato weevil incidence (weevil/m 2 ), severity (1-5 scale) and number of infested tubers. The data were subjected to Analysis of Variance (ANOVA) at p ≤ 0.05 and GENSTAT statistical package. Tukey’s test was used for mean separation. The results show that varieties, vine portion and cultural practices have significant effect on sweet potato weevil incidence and severity. With regard to variety, Mayai was significantly (p<0.05) had higher weevil incidence (LSD 0.397) than Mbirimbi and Shangazi. Using apical vine portion significantly (p<0.05) had low weevil severity (LSD 0.115) than middle and basal vine portions. Weeding and hilling-up thrice (12 WAP) significantly (p<0.05) had low weevil damage (LSD 0.768).

Commission of Science and Technology (COSTECH)