Essential Oils and Sulfur to Management Potato Late and Early Blight Diseases under Field Conditions

Both late and early blights caused by Phytophthora infestans and Aternaria solani respectively historically an important diseases of potato and tomato plants. Effect of Sulfur and some essential oils applied as alone or in combination to control late and early blight diseases of potato plants during two seasons was studied. The findings of laboratory investigations results revealed that Sulfur at 3.0 g/L and Thyme as well as Citral at 6.0 ml/L resulted in a total reduction in the linear growth of A. solani and P. infestans. In field trials, the data indicated the all tested treatments altogether decreased the late and early incidence during two seasons. Highest decrease in the incidence of late and early blight diseases was obtained with the combined treatments between Thyme + Sulfur and Citral + Sulfur, which reduced the late blight ranged between 83.3 and 88.2 %. and early blight between 69.2 and 76.9 %, respectively. As for the potato yield during the two winter planting seasons, the results showed that obtaining the highest increase in potato yield was achieved with the combination between Thyme + Sulfur and Citral + Sulfur, which led to an increase in potato yield ranged between 66.7 and 74.3 %. This treatments also showed an increase in potato yield during the two summer planting seasons, which led to an increase in potato yield ranged between 53.8 and 60.3 %. All previous treatments increased the enzyme activities.The best treatments are combined treatments between Thyme + Sulfur and Citral + Sulfur which increase peroxidase, chitinase and β,1-3- glucanase more than 300, 240 and 203.6 % respectively.