Effect of sowing depths on <i>Cylas </i> spp infestation on some sweetpotato varieties

Abstract

The effect of sowing depths on Cylas spp infestation of four sweetpotato varieties ‘Sauti’, ‘Okumkom’,‘Santompona’ and ‘Faara’ was determined in a field trial at Kwame Nkrumah University of Science and Technology. Data on number of leaves and branches on upper plant canopy (top 30cm), vine thickness, internode length, soluble sugar and dry matter content were taken and correlated with Cylas spp infestation. A two-factorial experiment was conducted using four sweetpotato varieties and three sowing depths in a Randomized Completely Block Design with three replications. The incidence of Cylas spp on the upper canopy of sweetpotato varieties after sowing increased from 2nd,3rd to the 4th month. There was significant increase in the incidence of weevil (P<0.01) with time on the four sweetpotato varieties. The tuber stalk length of the four sweetpotato varieties measured at harvest was highly significant (P<0.01).There was a negative correlation between percent tuber infestation and the three sowing depths. The level of tuber infestation of the four sweetpotato varieties by Cylas spp decreased with increasing depth of sowing. This may explain why sweetpotato varieties with long tuber stalk had the least incidence of Cylas spp. The results also indicated that the sweetpotato variety which had the highest number of leaves and branches, as well as the thickest vine had the highest incidence of vine infestation at 5% level. The sweetpotato varieties used had varying levels of soluble sugar and percent dry matter was also significant (P<0.05).

Key words; Cylas spp, dry matter, soluble sugar, sweetpotato,