Response of Digitaria sanguinalis and Setaria spp. populations to the ALS inhibitor herbicide nicosulfurón

Abstract

Digitaria sanguinalis and the species of the genus Setaria (S. adhaerens, S. verticillata and S. viridis) are among the most important grass weeds affecting maize cultivation in Spain. This study analyzed the response to the acetolactate synthase (ALS) inhibitor herbicide nicosulfurón of 23 D. sanguinalis populations and 20 Setaria spp. populations collected in a random survey conducted in maize fields in León, Salamanca, Zamora and Valladolid, the main growing areas of Castilla y León, in the year 2017. The plants were pre-germinated, transplanted and treated with nicosulfurón at a dose of 45 g. m.a. ha-1 at the 2-3 leaf stage. Four weeks after treatment the plants were evaluated and differentiated according to their phenotype in relation to an untreated control in: dead and/or severely damaged (susceptible), moderately damaged (intermediate resistance) and slightly damaged (resistant). Percentage of resistant plants was used to classify populations as susceptible, developing resistance or resistant. For Setaria spp. the plant mortality was 100% in all the populations. For D. sanguinalis, surviving plants were found in all populations with a mean frequency of 8.6 ± 6.9% (1.8-30.4%), with 96% of the populations developing resistance and one population (4%) from the province of León being classified as resistant. Data obtained will be useful to monitor the evolution of the resistance over time in the surveyed geographical regions.