Distribution and incidence of cylas puncticollis in sweet potato and their economic losses in small holder farming systems of Gairo district, Tanzania

Journal article

This study assessed the incidences, distributions and yield losses in sweet potatoes (Ipomoea batatas (L.) Lam) associated with Cylas puncticollis in small holder farming systems of Gairo District, Tanzania. This was accelerated by the fact that small holder farm ers produce sweet potatoes in areas with high risks of sweet potato weevils. At the farmer’s fields, plots measured 5m × 5m in each replicate, sweet potatoes were harvested and assessments were done on the variables such as number of weevils, species, roots infested by Cylas and areas infested (above-below ground). Two sweet potato varieties namely Morogoro and Shangazi in Mtumbatu village were involved. Results indicated that the number of weevils and their species were more in vines than in roots but serious damage was observed in roots. These were also more prevalent in variety Morogoro compared to variety Shangazi. The mean number of undamaged sweet potato was significantly (P<0.001) higher in Shangazi variety (54.7) compared to Morogoro variety (43.3). In addition, economic losses of marketable roots were highly caused by Cylas infestations (USD 306) in variety Morogoro and breaking (USD 425), cutting (282.5) and rotting (USD 67.5) in variety Shangazi. It was concluded that variety Morogoro is more susceptible to economic losses caused by Cylas infestations compared to variety Shangazi. Therefore, variety Morogoro should be harvested as early as it reaches maximum maturity and where possible farmers in Gairo District and similar areas should invest more on variety Shangazi.