ABSTRACT

 A survey was carried out in three locations (American quarters farm, National Root Crops and Research Institutes farm, Michael Okpara University of Agriculture, Umudike farm) to access the incidence and severity of bacterial leaf spot on three yam species (Dioscorea alata, Dioscorea rotundata and Dioscorea dumentorum) in Umudike. Also a field experiment and screen house trials were conducted at National Root Crops Research Institutes (NRCRI), Umudike, southeastern Nigeria to assess bacterial leaf spot disease ofthese three different yam species (Z>. alata, D. rotundata, D. dumentorum). Bacterial leafspot disease of yam was surveyed in the field during the 2016 cropping season. Results from the survey were based on varietal performance. D. alata (1166) variety recorded (4.58,5.67, 7.33, 8.08, 9.75 and 37.50%, 41.67%, 50.00%, 54.17%, 62.50%) for disease severity and incidence respectively, D. rotundata (Nwa) variety recorded (1.50, 2.75, 2.75, 3.58, 8.83 and 16.67%, 33.33%, 54.17%,66.67%,75.00%) for disease severity and incidence respectively and D. dumentorum (Ekpe) variety recorded (1.58, 2.58, 3.17, 4.58, 9.00 and 20.83%, 37.50%, 29.10%, 79.17%, 87.50%) for disease severity and incidence respectively. These three varieties (1166 for D. alata, Nwa for D. rotundata, and Ekpe for D. dumentorum) were all observed to be more susceptible than other varieties of the same species and the disease symptoms were more with increase in rainfall. Infected leaves were taken to the plant pathology laboratory for isolation and identification and pure culture obtained used for pathogenicity in the screen house. Both field and screen house trials conducted showed the potential of each extracts (Azadirachta indica, Eucalyptus officinalis, Cymbopogon citratus, Ocimum gratissimum) in controlling bacterial leafspot. Results obtained showed that all the plant extracts assessed reduced disease incidence and severity when compared with control (sterile water). A. indica recorded the best performance in growth and yield attributes (5.47kg) closely followed by C. citratus (4.34kg). Therefore the study shows that plant extracts could offer a safe alternative in management ofleafspot disease in Umudike