Interferência e nível de dano econômico de picão-preto sobre o feijão do tipo preto

Abstract

Bean is in the brazilian scenario as a crop with economic, social and cultural importance for smallholders farms. Among biotic factors that affect bean productivity and quality, weed infestation can be highlighted, being beggartick one of the most problematic species in southern Brazil. Beggarstick control decision based on the concept of economic injury level (NDE) allows farmers to adopt management practices only when damage caused by the weed is greater than the cost of control, making it an important measure for rational use of pesticides. Thus, the objective was to test mathematical models and identify explanatory variables in order to determine beggartick NDE depending on bean cultivar and weed population. The experiment was installed in the field in a randomized block design with no replication. Treatments consisted of six black bean cultivars (IPR 88 Uirapuru, BRS Supremo, BRS Campeiro, Fepagro 26, BRS Esplendor and IPR Tuiuiú) and ten beggarstick populations. Plant population (m2), leaf area (cm2 m-2), ground cover (%) and beggarstick shoot dry weight (g m-2) were assessed. The rectangular hyperbolic model was used to describe the relationship between productivity loss of bean and the explanatory variables in plants, soil cover, leaf area and beggarstick shoot dry mass. Losses in grain yield of beans due to interference of beggartick can be satisfactorily estimated by the hyperbolic model. Beggarstick plant population fits better to the model than shoot dry weight, ground cover or leaf area. The results show that cultivars respond differently to productivity losses when living with beggartick. NDE associated with the bean cultivar ranged from 0.74 to 8.72 beggartick plants m-2. The cultivars that were more competitive than beggartick were BRS Esplendor and IPR Tuiuiú.