Scutellonema bradys and Pratylenchus spp. associated with weeds in yam fields

Abstract

Summary Dry root disease of yam (Dioscorea spp.), caused by Scutellonema bradys, Pratylenchus coffeae and P. brachyurus, is prominent among the plant disease problems of yam in Brazil. In order to evaluate the association of these nematode species with weeds, field sampling was performed during 2016 and 2017 in yam-growing areas with a history of the disease within the major counties in the state of Alagoas, Brazil. The frequency of occurrence of both weeds and nematodes was determined, in addition to the estimated population of nematodes in roots. Forty-three weed species were found, of which 23 were infected with at least one of the causal agents of the dry rot disease, Pratylenchus spp. being the most prevalent in the fields. Ageratum conyzoides, Commelina benghalensis and Emilia coccinea (in Zona da Mata) and C. benghalensis (Agreste region) were especially important due to their high frequency of occurrence and also for supporting populations of S. bradys and Pratylenchus spp. Cyperus flavus, E. coccinea and Spermacoce verticillata are now recorded as new weed species associated with S. bradys.