LAUSR

The combination of plant density, fungicide, and levels of genotype resistance to white mold (WM) has not been studied for the role played in affecting performance of common bean with type III growth habit under WM pressure. We established four sprinkler-irrigated trials in the fall-winter season in Brazil, combining density (8, 14, 20 or 26 plants/m2), genotype (susceptible or partially resistant to WM), and fungicide to manage WM (two fluazinam applications or without fluazinam) at 0.5 m row spacing in fields infested with sclerotia. One trial was established in a warm region, aiming to obtain low WM pressure. For three trials, the linear mixed model was used. WM pressure in the trials ranged from low to high. Genotype × density × fungicide and genotype × density interactions were not significant for incidence, severity, and yield for all trials. In the three trials, severity was 29% lower at 8 than at 26 plants/m2, and yield at 14 plants/m2 (3,294 kg/ha) was 14% higher than yield at 8 plants/m2 (P = 0.035) where fluazinam was applied. However, without fluazinam, density did not affect yield. In conclusion, plant density for type III bean cultivars does not need to take into account their resistance levels to WM in the fall-winter season. However, fungicide treatment to manage WM affects the decision on density, with 8 to 12 plants/m2 recommended if fungicide is not an option to manage WM (as in organic systems), and 10 to 14 plants/m2 recommended if fungicide applications are likely.