$\mathrm{DI},\%=\frac{\mathsf{\Sigma }\left(\mathrm{d}\times {\mathrm{n}}_1\right)}{4\mathrm{n}}\times 100$	0 - no disease symptoms
	1- weak symptoms (brown streaks or spots) on roots and above
	2 - are manifest, but medium symptoms
	3 - strong extensive symptoms
	4 - crown and root decaying or plant death