Where ni ¼ number of plants with the respective disease rating; vi ¼ the disease rating; V ¼ the highest disease rating (5); and N ¼ the total number of observed plants.The disease rating was calculated using the following scale:
0: no symptoms;
1: up to 10% of the leaf area wilted;
2: 11-40% of the leaf area wilted;
3: 41-60% of the leaf area wilted,
4: 61-85 of the leaf area wilted and
5: >85% of the leaf area wilted or leaf is dead.