2.11. Calculation of disease severity
The degrees of the severity of A. vera leaf spot disease in the
course of experiments carried on in the greenhouse as well as on
the field were rated as follows (Panwar et al., 2013): 0 – no leaf
spot symptoms; 1 – up to 1% leaves area covered by symptoms;
3 – 1–10% leaves area covered by symptoms; 5 – 11–25% leaves
area covered by symptoms; 7 – 26–50% leaves area covered by
symptoms and 9 – >50% leaves area covered by symptoms. At
intervals of 15 days disease severities were calculated according
to the formula: Disease severity = {Sum of all disease rating/Total
number of rating Maximum disease grade} 100.