Fusarium blight, caused by fungi of the genus Fusarium Link, is one of the damaging diseases of white mustard, black mustard and spring false flax. In the development of new varieties of these crops, it is necessary to carry out an annual evaluation of the varieties’ resistance to the disease. In order to improve the breeding process, it is necessary to carry out a laboratory evaluation in addition to the field evaluation of the resistance of samples to Fusarium blight. The existing method of evaluation is labor-intensive and time-consuming, so we carried out research to modify this method. As a result of the research, a 5-point scale was developed for Fusarium blight affection of seedlings of the studied crops when infected with Fusarium oxysporum Schlecht. emend. Synd. et Hans. We found that the evaluation of breeding material of black mustard is reliable when exposed for 5 hours and recorded on the day of the experiment. The evaluation of breeding material of white mustard and spring false flax is also objective at the exposure time of 5 hours, but with the recording of seedling affection by the disease 1 day after the end of the exposure time of the experiment.