Abstract:
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).
