Sweet potato Weevil (Cylas puncticollis) Boheman Infestation: Cultivar Differences and the Effects of Mulching

The effects of infestation by the sweet potato weevil, Cylas puncticollis Bohemen, on yield in 3 sweet potato cultivars, in relation to different mulching levels were compared. The experiment was laid out in a randomized complete split plot design at three levels. It consisted of a main plot factor, the three sweet potato cultivars (slipot 2, 3 and 4) with mulching at three levels (0, 1, 3 and 5t/ha) as sub plot. The factors were replicated thrice. The results of the studies re- vealed that increase in mulching level resulted in significantly decreased infestation of sweet potato weevil and higher root yield. Mulching at the rate of 5t/ha recorded the least infestation (12.13% for the year 2012; 13.32% for the year 2013) followed by 3t/ha (17.86% for the year 2012; 21.24% for the year 2013), 1t/ha (25.18% for the year 2012; 29.49% for the year 2013) whilst the unmulched plot recorded the highest (35.75% for the year 2012; 41.30% for the year 2013). Root yield was the highest with mulching at the rate of 5t/ha (6242.42Kg/ha for the year 2012; 4828.45Kg/ha for the year 2013) followed by 3t/ha (5863.64Kg/ha for the year 2012; 4883.82Kg/ha for the year 2013), 1t/ha (4580.81Kg/ha for the year 2012; 3818.18Kg/ha for the year 2013) whilst the unmulched plot recorded the highest (4202.03Kg/ha for the year 2012; 3489.89Kg/ha for the year 2013). Significant negative correlation (r = -0.91, p = 0.0001) was observed between weevil root damage and root dry matter. Only two cultivars, Slipot 3 and Slipot 4 were observed to be less susceptible to the sweetpoto weevil. Thus, using mulch cover at the rate of 3- 5t/ha in a field planted with slipot 3 or slipot 4 will in- crease yield, while at same time reduce sweet potato weevil infestation.