Sweetpotato infestation by Cylas spp. in East Africa: Ii. Investigating the role of root characteristics

Abstract

The response of the sweetpotato weevil Cylas puncticollis (Coleoptera: Brentidae) to roots of different sweetpotato cvs was investigated as part of a project to examine the factors that affect susceptibility of sweetpotato cvs to weevil infestation in the field. Laboratory experiments were conducted at two sites (Ukiriguru and Kibaha) in Tanzania and at one site (Serere) in Uganda to determine if the harvested storage roots of sweetpotato cvs differed in their acceptability to C. puncticollis or if any root antibiosis towards C. puncticollis existed. For all experiments cultivar effects for the total number of emerging adults were significant to at least 10% and in most cases were much more significant. At Ukiriguru and Kibaha, the results showed reasonable consistency between years, and of the four cultivars used at both sites, fewer C. puncticollis adults emerged from roots of Sinia and Budagala than from SPN/0 and Mwanamonde on all occasions. A relationship between laboratory experiments and crown damage by Cylas spp. in the field suggests that cultivar differences in attraction/deterrence for Cylas spp. exist. However, correlations between adult emergence in laboratory antibiosis experiments and field infestation levels were generally not strong. Although this indicates that cultivar selection by laboratory experiments is not a useful strategy for reducing field infestation, there may be potential for using such techniques to select cultivars that are resistant to attack during long-term storage.