2.9.3. Criteria used to determine the disease intensity and quantification of the effectiveness of preventative treatments

The criteria used to classify the disease were as follows (NY/T, 3621-2020, Agricultural industry standard of the People's Republic of China, 2020): Grade 0, normal root system, asymptomatic; Grade 1, small clubbed roots <0.5 cm in diameter formed on one-third or fewer lateral roots, no clubbing on the main root; Grade 2, one-third to two-third of the lateral roots had clubbing, or the diameter or length of clubbing on the main root <3 times the diameter of stem base; Grade 3, two-third or more of the lateral roots exhibited clubbing, which was obvious on the main root, and the diameter or length of clubbing >3 times the diameter of stem base, or the clubbed roots were ulcerated.