Assessment of Sweet Potato (Ipomoea batatas Lam.) Viral Diseases and Homopterous Insects in Wolaita Zone, Southern Ethiopia

Abstract

The study was conducted in sweet potato fields to determine the current distribution of common sweet potato viral diseases and homopterous insect pests in Wolaita zone, Southern Ethiopia. A total of 60 sweet potato fields were examined for incidence and severity of viral diseases. Based on the observations of the symptoms all of the surveyed fields (100%) showed virus-like symptoms due to virus infection or other factors inducing similar responses. For the virus identification, 300 symptomatic and 20 asymptomatic sweet potato samples were collected from farmers’ fields of which an average of 38.7% of symptomatic and 25% of the symptomless samples were positive for at least one virus by ELISA test. The most prevalent sweet potato infecting viruses detected throughout the study areas were Sweet potato chlorotic stunt virus (SPCSV), (14.7 to 84 %) Sweet potato feathery mottle virus (SPFMV) (13.3 to 21.3%) and Sweet potato chlorotic fleck virus (SPCFV) (4.5%) in order of their prevalence. Mixed (dual and triple) infections were also common. Incidences of co-infection by SPCSV and SPFMV reached 20% in Damot Galle. Mixed infections by SPCFV+SPCSV and SPCFV+SPCSV+SPFMV were about 13.6% and 31.8%, respectively. Sweep net and pan trap collections of homopterous insects during the vegetative growth of sweet potato crops indicated that Cicadellidae family was the most prevalent followed by family Cercopoidea. Whiteflies were predominant while aphids were absent during the survey periods. A total of 600 symptomatic and 200 asymptomatic sweet potato plants were randomly harvested from farmers’ fields at maturity. Significant yield differences were obtained and the average mean weights of tuber yield from symptomatic and symptomless plants were 0.21 kg and 0.65 kg per plant, respectively. The study showed that the incidence and severity of sweet potato viral diseases had a significant positive relation with insect abundance and a significant negative relationship with sweet potato yield. Our study was only from four districts and more studies of a wider scale are recommended on assessments of viruses and vectors on sweet potatoes in different agroecologies in Ethiopia.