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

ABSTRACT

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 revealed 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 increase yield, while at same time reduce sweet potato weevil infestation.

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