Increased susceptibility to Fusarium oxysporum is one of the most conspicuous characteristics of the Arabidopsis mutants lacking the heterotrimeric G protein β and γ1 subunits. The molecular mechanisms placing these G proteins in the plant innate immunity network are yet to be discovered. However, a method to test susceptibility to and disease progression of an important plant pathogen, such as F. oxysporum, is of central importance to many plant defense studies. The optimized protocol presented here allows the routine processing and analysis of symptom progression in young Arabidopsis soil-grown seedlings and yields highly reproducible results.